TY - JOUR A1 - Monkman, Gareth J. A1 - Sindersberger, Dirk A1 - Prem, Nina T1 - Magnetically enhanced photoconductive high voltage control JF - ISSS Journal of Micro and Smart Systems N2 - The recent surge of interest in electrostatic actuators, particularly for soft robotic applications, has placed increasing demands on high voltage control technology. In this respect, optoelectronic bidirectional switching and analogue regulation of high voltages is becoming increasingly important. One common problem is the leakage current due to dark resistance of the material or device used. Another is the physical size of such elements. However, their ability to provide galvanic separation makes them a very attractive alternative to conventional (wired) semiconductor elements. This paper gives an overview of available methods and devices before introducing a concept based on the combination of photoresistive and magnetoresistive effects in Gallium Arsenide that are potentially applicable to other semiconductor materials. KW - GaAs KW - High voltage actuators KW - Magnetoresistance KW - Opto-sensors KW - Photoconduction KW - Soft robotics Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-30606 N1 - Corresponding author: Gareth J. Monkman VL - 11 SP - 317 EP - 328 PB - Springer Nature ER - TY - JOUR A1 - Monkman, Gareth J. A1 - Striegl, Birgit A1 - Prem, Nina A1 - Sindersberger, Dirk T1 - Electrical Properties of Magnetoactive Boron‐Organo‐Silicon Oxide Polymers JF - Macromolecular Chemistry and Physics N2 - The electrical properties of rheopectic magnetoactive composites comprising boron-organo-silicon oxide dielectric matrices containing carbonyl iron microparticles are presented for the first time. The increase in interfacial magnetocapacitance is seen to greatly exceed that experienced when using conventional elastomeric matrices such as polydimethylsiloxane. In addition to the increase in capacitance, a simultaneous and sharp decrease in the parallel electrical resistance over several orders of magnitude is also observed. The effects are time dependent but repeatable. Potential applications include magnetically controlled frequency dependent devices, magnetic sensor systems, weighting elements for neural networks, etc. Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-26488 N1 - Corresponding author: Gareth J. Monkman VL - 221 IS - 4 SP - 1 EP - 8 PB - Wiley ER - TY - JOUR A1 - Prem, Nina A1 - Sindersberger, Dirk A1 - Monkman, Gareth J. T1 - Infrared spectral analysis of low concentration magnetoactive polymers JF - Journal of Applied Polymer Science N2 - This work concerns an area of magnetoactive polymer (MAP) research seldom considered. Traditionally only MAP with high concentrations of magnetic filler (typically between 10 and 90 wt%) have been investigated. This article deals with a hitherto neglected aspect of research, namely MAP containing lower magnetic filler concentrations (1 to 3 wt%). This article utilizes a range of spectroscopic analysis methods (Raman and FTIR) and their applicability to MAP characterization at wavelengths ranging from 2.5 to 25 mu m. Particular attention is paid to low carbonyl iron particle (CIP) concentrations in MAP for which the emergence of capillary doublets at a critical 2 wt% concentration is revealed. This results in measurable magnetic field-dependent changes in IR absorption at a wavelength of 4.255 mu m together with a detectable CO2 susceptibility. (c) 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48366. KW - ELASTOMERS KW - magnetism and magnetic properties KW - sensors and actuators KW - spectroscopy Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-25913 SN - 1097-4628 N1 - Corresponding author: Nina Prem VL - 137 IS - 7 SP - 1 EP - 7 PB - Wiley ER - TY - JOUR A1 - Monkman, Gareth J. A1 - Egersdörfer, Stefan A1 - Meier, Alexander A1 - Böse, Holger A1 - Baumann, Michael A1 - Ermert, Helmut A1 - Kahled, W. A1 - Freimuth, Herbert T1 - Technologies for Haptic Displays in Teleoperation JF - Industrial Robot N2 - Since the 1960s many alphanumeric to tactile data conversion methods have been investigated, mainly with the ultimate aim of assisting the blind. More recently, interest has been directed toward the display of pictures on haptically explorable surfaces – tactile imaging – for a range of medical, remote sensing and entertainment purposes. This paper examines the technologies which have been utilised for haptically explorable tactile displays over the past three decades, focussing on those which appear commercially viable in the immediate future. Y1 - 2003 U6 - https://doi.org/10.1108/01439910310506792 SN - 0143-991x VL - 30 IS - 6 SP - 525 EP - 530 PB - Emerald ER - TY - JOUR A1 - Prem, Nina A1 - Sindersberger, Dirk A1 - Striegl, Birgit A1 - Böhm, Valter A1 - Monkman, Gareth J. T1 - Shape memory effects using magnetoactive Boron-organo-silicon oxide polymers JF - Macromolecular Chemistry and Physics N2 - Thermomechanical shape memory materials have certain disadvantages when it comes to 3D volumetric reproduction intended for rapid prototyping or robotic prehension. The need to constantly supply energy to counteract elastic retraction forces in order to maintain the required geometry, together with the inability to achieve conformal stability at elevated temperatures, limits the application of thermal shape memory polymers. Form removal also presents problems as most viscoelastic materials do not ensure demolding stability. This work demonstrates how magnetoactive boron−organo−silicon oxide polymers under the influence of an applied magnetic field can be used to achieve energy free sustainable volumetric shape memory effects over extended periods. The rheopectic properties of boron−organo−silicon oxide materials sustain form removal without mold distortion. Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-23205 N1 - Corresponding Author: Gareth J. Monkman VL - 221 IS - 15 SP - 1 EP - 8 PB - Wiley ER - TY - JOUR A1 - Mayer, Matthias A1 - Rabindranath, Raman A1 - Börner, Juliane A1 - Hörner, Eva A1 - Bentz, Alexander A1 - Salgado, Josefina A1 - Han, Hong A1 - Böse, Holger A1 - Probst, Jörn A1 - Shamonin (Chamonine), Mikhail A1 - Monkman, Gareth J. A1 - Schlunck, Günther T1 - Ultra-Soft PDMS-Based Magnetoactive Elastomers as Dynamic Cell Culture Substrata JF - PLoS ONE N2 - Mechanical cues such as extracellular matrix stiffness and movement have a major impact on cell differentiation and function. To replicate these biological features in vitro, soft substrata with tunable elasticity and the possibility for controlled surface translocation are desirable. Here we report on the use of ultra-soft (Young’s modulus <100 kPa) PDMS-based magnetoactive elastomers (MAE) as suitable cell culture substrata. Soft non-viscous PDMS (<18 kPa) is produced using a modified extended crosslinker. MAEs are generated by embedding magnetic microparticles into a soft PDMS matrix. Both substrata yield an elasticity-dependent (14 vs. 100 kPa) modulation of α-smooth muscle actin expression in primary human fibroblasts. To allow for static or dynamic control of MAE material properties, we devise low magnetic field (≈40 mT) stimulation systems compatible with cell-culture environments. Magnetic field-instigated stiffening (14 to 200 kPa) of soft MAE enhances the spreading of primary human fibroblasts and decreases PAX-7 transcription in human mesenchymal stem cells. Pulsatile MAE movements are generated using oscillating magnetic fields and are well tolerated by adherent human fibroblasts. This MAE system provides spatial and temporal control of substratum material characteristics and permits novel designs when used as dynamic cell culture substrata or cell culture-coated actuator in tissue engineering applications or biomedical devices. Y1 - 2013 U6 - https://doi.org/10.1371/journal.pone.0076196 VL - 8 IS - 10 PB - PLOS ER - TY - JOUR A1 - Forster, Eva A1 - Mayer, Matthias A1 - Rabindranath, Raman A1 - Böse, Holger A1 - Schlunck, Günther A1 - Monkman, Gareth J. A1 - Shamonin (Chamonine), Mikhail T1 - Patterning of ultrasoft, agglutinative magnetorheological elastomers JF - Journal of applied polymer science N2 - A low-cost wax-cast molding technique for structuring ultrasoft (Young’s modulus ≤ 40 kPa), agglutinative magnetorheological elastomer (MRE) material is presented. MRE structures ranging from a few millimeters down to the micrometer range with highly reproducible results are possible. Semitransparent MREs are also fabricated and their surfaces modified accordingly. This method opens new possibilities for MREs in biomedical engineering and microfluidic applications. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 Y1 - 2013 U6 - https://doi.org/10.1002/app.38500 VL - 128 IS - 4 SP - 2508 EP - 2515 PB - Wiley CY - New York, NY ER - TY - JOUR A1 - Diermeier, Andreas A1 - Sindersberger, Dirk A1 - Krenkel, Lars A1 - Rosell, X. C. A1 - Monkman, Gareth J. T1 - Controllable Magnetoactive Polymer Conduit JF - The Open Mechanical Engineering Journal N2 - Objective: Magneto-active Polymers (MAP) are smart materials whose mechanical characteristics, such as elastic and shear moduli, may be controllable by means of an externally applied magnetic field. Methods: Various additives may be used to influence the characteristics of the polymer matrix whilst a suspension of soft and/or hard magnetic particles determine the magnetic properties of the composite. Both pre-cure and post-cure magnetization is possible. Results: A range of control strategies have been investigated for evaluation of the system using fluids of differing kinematic viscosity. Conclusion: Depending on the degree of magnetic field homogeneity, magneto-deformation and magnetostriction contribute to MAP actuation. This paper presents a novel application in the form of a peristaltic MAP tube system, applicable to flow control and pumping of hemorheological fluids in blood circulatory systems for biomedical research purposes. Y1 - 2018 UR - https://www.benthamopen.com/ABSTRACT/TOMEJ-12-192 N1 - Corresponding authro: Gareth J. Monkman VL - 12 IS - 1 SP - 192 EP - 200 PB - Bentham ER - TY - JOUR A1 - Loo, Xuyan A1 - Nagaraju, Bhavana A1 - Pathivada, Sai A1 - Bartsch, Alexander A1 - Schratzenstaller, Thomas A1 - Sattler, Robert A1 - Monkman, Gareth J. T1 - Electrical properties of bisphenol-A-free magnetoactive borosilicate polymers JF - AIP Advances N2 - The recent REACH regulations require the elimination of bisphenol-A and titanium dioxide from commercially available boron-based polymers. This has led to changes in some of the mechanical characteristics, which strongly influence the properties of magnetoactive borosilicate polymers. This work delivers results on the electrical properties and discusses some implications for future research using bisphenol-A and titanium-dioxide-free substitutes. KW - Electrical components KW - Electrical properties and parameters KW - Dielectric properties KW - Electrical resistivity KW - Magnetic materials KW - Viscoelasticity KW - Polymers KW - Non Newtonian fluids KW - Magnetic fluids Y1 - 2024 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-72936 SN - 2158-3226 N1 - Corresponding author der OTH Regensburg: Gareth J. Monkman VL - 14 IS - 5 PB - AIP Publishing ER - TY - JOUR A1 - Sorokin, Vladislav V. A1 - Stepanov, Gennady V. A1 - Shamonin (Chamonine), Mikhail A1 - Monkman, Gareth J. A1 - Khokhlov, Alexei R. A1 - Kramarenko, Elena Yu T1 - Hysteresis of the viscoelastic properties and the normal force in magnetically and mechanically soft magnetoactive elastomers: Effects of filler composition, strain amplitude and magnetic field JF - Polymer N2 - Hysteresis in dynamic modulus, loss factor and normal forces of magnetoactive elastomers (MAEs) comprising various proportions of small (3-5 mu m) and large (50-60 mu m) ferromagnetic particles are experimentally studied using dynamic torsion performed at a fixed oscillation frequency in varying DC magnetic fields. It is shown that hysteresis is a characteristic feature of MAEs observed both under increasing/decreasing magnetic field strength and increasing/decreasing strain amplitude. This hysteresis is attributed to the specific rearrangement of the magnetic filler network under simultaneously applied magnetic field and shear deformation. Rheological properties of the magnetic filler network formed in the magnetic field and, therefore, the rheological properties of MAEs depend strongly on the filler composition and the magnetic field magnitude. Larger magnetic particles and higher magnetic fields provide stronger magnetic networks. Both factors result in the extension of the linear viscoelastic regime to larger strain amplitudes and lead to higher values of shear storage and loss moduli. It is found that the hysteresis width maximises at an intermediate magnetic field where it is attributed to the balance between elastic and magnetic particle interactions. This is apparently where the most significant restructuring of the magnetic network occurs. The hysteresis width decreases with increasing fraction of large particles in the magnetic filler. The loss factor grows significantly when the magnetic network is physically broken by large strains gamma > 1%. A huge (more than one order of magnitude) increase of normal force at maximum magnetic field strengths is observed. It is predicted that any physical quantity depending on the internal structuring of the magnetic filler should demonstrate hysteresis either with a changing magnetic field and constant deformation amplitude or under variable deformation in a constant magnetic field. (C) 2015 Elsevier Ltd. All rights reserved. KW - BEHAVIOR KW - COMPRESSION KW - Dynamic modulus KW - GELS KW - hysteresis KW - Magnetorheological elastomers KW - magnetostriction KW - MODULUS KW - PARTICLES KW - POLYMER COMPOSITES KW - shear Y1 - 2015 U6 - https://doi.org/10.1016/j.polymer.2015.08.040 VL - 76 SP - 191 EP - 202 PB - Elsevier ER - TY - JOUR A1 - Monkman, Gareth J. A1 - Sindersberger, Dirk A1 - Diermeier, Andreas A1 - Prem, Nina T1 - The magnetoactive electret JF - smart materials and structures N2 - A magnet which adheres to every surface, not only those of ferromagnetic materials, has hitherto been the domain of science fiction. Now for the first time such a novel device exists. The fusion of a permanently magnetized magnetoactive polymer containing hard magnetic particles and an electret enhanced with ferroelectric particles has resulted in the development of a new smart device-the magnetoactive electret. Magnetoactive electrets can be made to exhibit the usual magnetic properties of permanent magnetism together with the electrostatic properties of electrets. This results in simultaneous magnetoadhesion and electroadhesion forces from the same elastomeric element. The biasing field, needed to avoid discontinuities concerned with transition through the zero point in operating curves, is normally provided by means of either a magnetic or an electric field. This novel technology provides both bias options in a single device. KW - 6D printing KW - electret KW - electroadhesion KW - FLUIDS KW - MAGNETIC-FIELD KW - magnetoactive electret KW - magnetoactive polymer KW - magnetoadhesion KW - Magnetorheological elastomers KW - RHEOLOGY Y1 - 2017 U6 - https://doi.org/10.1088/1361-665X/aa738f VL - 26 IS - 7 PB - IOP Publishing ER - TY - JOUR A1 - Monkman, Gareth J. A1 - Sindersberger, Dirk A1 - Prem, Nina A1 - Diermeier, Andreas A1 - Szecsey, Tamara T1 - Dielectric behaviour of magnetic hybrid materials JF - Physical Sciences Reviews N2 - The objectives of this work include the analysis of electrical and magnetic properties of magneto-elastic hybrid materials with the intention of developing new techniques for sensor and actuator applications. This includes the investigation of dielectric properties at both low and high frequencies. The behaviour of capacitors whose dielectrics comprise magnetic hybrid materials is well known. Such interfacial magnetocapacitance can be varied according to magnetic content, magnetic flux density and the relative permittivity of the polymer matrix together with other dielectric content. The basic function of trapping electrical charges in polymers (electrets) is also established technology. However, the combination of magnetoactive polymers and electrets has led to the first electromagnetic device capable of adhering to almost any material, whether magnetically susceptible or not. During the course of this research, in addition to dielectrics, electrically conductive polymers based on (PDMS) matrices were developed in order to vary the electrical properties of the material in a targeted manner. In order to ensure repeatable results, this demanded new fabrication techniques hitherto unavailable. The 3D printing of silicones is far from being a mature technology and much pioneering work was necessary before extending the usual 3 d.o.f. to include orientation about and diffusion of particles in these three axes, thus leading to the concept of 6D printing. In 6D printing, the application of a magnetic field can be used during the curing process to control the particulate distribution and thus the spatial filler particle density as desired. Most of the devices (sensors and actuators) produced by such methods contain levels of carbonyl iron powder (CIP) embedded magnetic filler of up to 70 wt%. Contrary to this, a hitherto neglected research area, namely magnetoactive polymers (MAPs) having significantly lower magnetic particle concentrations (1 to 3 wt% CIP) were also investigated. With filler concentrations lower than 3 wt%, structures are formed which are completely absent at higher filler levels. CIP concentrations in the range of 1wt% demonstrate the formation of toroidal structures. Further development of coherent rings with a compact order results as filler concentrations increase towards 2 wt%. Above 3 wt% the structure eventually disintegrates to the usual random order found in traditional MAP with higher CIP content. Structured samples containing 1%–3 wt% CIP were investigated with the aid of X-ray tomography where solitary ring structures can be observed and eventually the formation of capillary doubles. Over wavelengths ranging from 1 to 25 µm, spectroscopic analysis of thin film MAP samples containing 2 wt% CIP revealed measurable magnetic-field-dependent changes in IR absorption at a wavenumber 2350 (λ = 4.255 µm). This was found to be due to the diamagnetic susceptibility of atmospheric carbon dioxide (CO2). Consequently, the first potential application for sparse matrix MAPs was found. KW - cappillary doublet KW - diamagnetic KW - elastomer dielectric KW - FTIR KW - interfacial magnetocapacitance KW - magnetoactive polymer KW - PDMS KW - toroid Y1 - 2021 U6 - https://doi.org/10.1515/psr-2019-0121 N1 - Corresponding author: Gareth J. Monkman VL - 7 IS - 10 SP - 1169 EP - 1185 PB - de Gruyter ER - TY - JOUR A1 - Prem, Nina A1 - Sindersberger, Dirk A1 - Monkman, Gareth J. T1 - Mini-Extruder for 3D Magnetoactive Polymer Printing JF - Advances in Materials Science and Engineering N2 - This work describes the development of a new miniature extruder, essential to cavity-free 3D printing of silicone-based smart materials. This makes the 3D printing of magnetoactive and electroactive polymer soft robotic components and devices directly from CAD data possible. The special feature of such an extruder is that it is designed for use with addition-crosslinking RTV-2 silicones, including solid particulate additives. The extruder merges the respective components automatically during extrusion which obviates the need for premixing and vacuum evacuation. Problems associated with inhomogeneities and unwanted cavity production are consequently eliminated. Rheological details necessary to the design, together with some preliminary performance results, are presented. Y1 - 2019 U6 - https://doi.org/10.1155/2019/8715718 N1 - Corresponding author: Gareth J. Monkman SP - 1 EP - 8 PB - HINDAWI ER - TY - JOUR A1 - Kreitmeier, Florian A1 - Chashin, Dmitri V. A1 - Fetisov, Yuri K. A1 - Fetisov, Leonid Y. A1 - Schulz, Irene A1 - Monkman, Gareth J. A1 - Shamonin (Chamonine), Mikhail T1 - Nonlinear Magnetoelectric Response of Planar Ferromagnetic-Piezoelectric Structures to Sub-Millisecond Magnetic Pulses JF - Sensors N2 - The magnetoelectric response of bi- and symmetric trilayer composite structures to pulsed magnetic fields is experimentally investigated in detail. The structures comprise layers of commercially available piezoelectric (lead zirconate titanate) and magnetostrictive (permendur or nickel) materials. The magnetic-field pulses have the form of a half-wave sine function with duration of 450 µs and amplitudes ranging from 500 Oe to 38 kOe. The time dependence of the resulting voltage is presented and explained by theoretical estimations. Appearance of voltage oscillations with frequencies much larger than the reciprocal pulse length is observed for sufficiently large amplitudes (~1-10 kOe) of the magnetic-field pulse. The origin of these oscillations is the excitation of bending and planar acoustic oscillations in the structures. Dependencies of the magnetoelectric voltage coefficient on the excitation frequency and the applied magnetic field are calculated by digital signal processing and compared with those obtained by the method of harmonic field modulation. The results are of interest for developing magnetoelectric sensors of pulsed magnetic fields as well as for rapid characterization of magnetoelectric composite structures. Y1 - 2012 U6 - https://doi.org/10.3390/s121114821 N1 - Corresponding author: Mikhail Shamonin VL - 12 IS - 11 SP - 14821 EP - 14837 PB - MDPI CY - Basel ER - TY - JOUR A1 - Monkman, Gareth J. A1 - Sindersberger, Dirk A1 - Prem, Nina A1 - Szecsey, Tamara T1 - Smart Stiction JF - Robotics & Automation Engineering Journal N2 - Soft robotics could loosely be described as the engineering science of expanded dexterity through controllable flexibility. The exploitation of controllable compliance through the judicious choice of soft flexible members, as opposed to a finite number of rigid kinematic joints, can result in greater dexterity without compromising simplicity. One example is the replacement of segmented mechanical legs with simple compliant material eruciform prolegs. To achieve this in robotics, without introducing additional mechanical joints, mobile surfaces with switchable coefficients of friction is essential. This paper explains how, using silicone based smart materials, the rapid alternation between kinematic and static friction (stiction) may be achieved. Y1 - 2019 U6 - https://doi.org/10.19080/RAEJ.2019.04.555641 N1 - Corresponding author: Gareth J. Monkman VL - 4 IS - 4 PB - Juniper Publishers ER - TY - JOUR A1 - Sindersberger, Dirk A1 - Prem, Nina A1 - Monkman, Gareth J. T1 - Structure formation in low concentration magnetoactive polymers JF - AIP advances N2 - This paper concerns recent research into the autonomous formation of micro-structures in low carbonyl iron powder (CIP) concentration magneto active polymers (MAP). Higher concentrations of CIP show an isotropic distribution of magnetic filler throughout the entire sample, while autonomous structure formation is possible at mass concentrations lower than 3%. The formation of micro-toroids commences as CIP concentration approaches 1% wt. Further development of coherent rings with a defined order follow as CIP concentrations increase toward 2% wt, whilst exceeding 3% wt leads to the same isotropic distribution found in higher concentration MAP. Structured samples containing between 1% wt and 3% wt CIP were investigated using X-Ray tomography where solitary structures could clearly be observed. The ring structures represent microinductivities whose geometries can be manipulated during fabrication. In addition, these structures are magnetic field sensitive. This is not only relevant to applications in the GHz and THz areas but recent research has revealed implications for optical, thermal, acoustic and even chemical MAP sensors. (C) 2019 Author(s). Y1 - 2019 U6 - https://doi.org/10.1063/1.5079997 N1 - Corresponding author: Dirk Sindersberger VL - 9 IS - 3 PB - AIP Publishing ER - TY - JOUR A1 - Chen, Rui A1 - Zhang, Zhuo A1 - Song, Ruizhou A1 - Fang, Cheng A1 - Sindersberger, Dirk A1 - Monkman, Gareth J. A1 - Guo, Jianglong T1 - Time-dependent electroadhesive force degradation JF - Smart Materials and Structures N2 - This paper concerns a comprehensive investigation of time-dependent electroadhesion (EA) force degradation. EA shear force tests on different object materials (a PET, glass, ABS, and wood plate) have shown that force degradation was dominated by residual polarization charges trapped in the EA pad dielectric rather than in the substrate dielectric from which the object to be prehended is made. In order to explain this dynamic physical phenomenon, a model of dielectric polarization and depolarization has been proposed. According to the derived relationship between EA force and discharge time, three different methods intended to mitigate this problem has been compared: (1) the natural discharge method, (2) the high voltage resistor discharge method, and (3) the discharge prior to field polarity reversal method. These methods are useful for generating repeatable and stable EA forces, which are required for the characterization of EA pads and their subsequent employment in material handling, mobile robot crawling and climbing tasks. Y1 - 2020 U6 - https://doi.org/10.1088/1361-665X/ab79b5 VL - 29 IS - 5 PB - IOP Publishing ER - TY - JOUR A1 - Schmidt, Henrik A1 - Straub, Benedikt B. A1 - Sindersberger, Dirk A1 - Bröckel, Ulrich A1 - Monkman, Gareth J. A1 - Auernhammer, Günter T1 - Collision and separation of nickel particles embedded in a Poly dimethylsiloxan matrix under a rotating magnetic field: A strong magneto active function JF - Colloid and Polymer Science N2 - In order to function as soft actuators, depending on their field of use, magnetorheological elastomers (MREs) must fulfill certain criteria. To name just a few, these can include rapid response to external magnetic fields, mechanical durability, mechanical strength, and/or large deformation. Of particular interest are MREs which produce macroscopic deformation for small external magnetic field variations. This work demonstrates how this can be achieved by just a small change in magnetic field orientation. To achieve this, (super)paramagnetic nickel particles of size ≈ 160 μm were embedded in a non-magnetic polydimethylsiloxan (PDMS) (661–1301 Pa) and their displacement in a stepwise rotated magnetic field (170 mT) recorded using a video microscope. Changes in particle aggregation resulting from very small variations in magnetic field orientation led to the observation of a new strongly magneto-active effect. This configuration is characterized by an interparticle distance in relation to the angle difference between magnetic field and particle axis. This causes a strong matrix deformation which in turn demonstrates hysteresis on relaxation. It is shown that the occurrence strongly depends on the particle size, particle distance, and stiffness of the matrix. Choosing the correct parameter combination, the state can be suppressed and the particle-matrix system demonstrates no displacement or hysteresis. In addition, evidences of non-negligible higher order magnetization effects are experimentally ascertained which is qualitatively in agreement with similar, already theoretically described, particle systems. Even at larger particle geometries, the new strongly magneto-active configuration is preserved and could create macroscopic deformation changes. Y1 - 2021 U6 - https://doi.org/10.1007/s00396-020-04784-4 VL - 299 SP - 955 EP - 967 PB - Springer ER - TY - CHAP A1 - Sefl, Ondrej A1 - Prochazka, Radek A1 - Haller, Rainer A1 - Monkman, Gareth J. T1 - Alternative Approach to Optical Detection of Partial Discharges in Air T2 - 2021 IEEE Conference on Electrical Insulation and Dielectric Phenomena (CEIDP): 12-15 Dec. 2021, Vancouver, BC, Canada N2 - This article compares the standard electrical method of partial discharge detection with a novel optical detection method based on silicon photomultipliers. A third, complementary, single-loop antenna method is added to represent the ultra-high frequency method commonly used in gas-insulated switchgear/lines. A trio of air-insulated electrode designs that simulate the fundamental fault/discharge types in gaseous insulation (protrusion – corona discharge, floating conductive particle, surface discharges) are employed. Phase-resolved partial discharge activity patterns are compiled for each electrode design. The patterns are analyzed using spatial statistics and the interpretation of the obtained data trends explained by means of an example. Ultimately, the consistency and reliability of discharge detection by the optical methods for each fault/discharge type are evaluated, and suggestions for improvement are made. KW - gas insulated switchgear KW - loop antennas KW - partial discharges KW - photomultipliers KW - reliability KW - statistical analysis KW - surface discharges Y1 - 2021 SN - 978-1-6654-1907-9 U6 - https://doi.org/10.1109/CEIDP50766.2021.9705350 SN - 2576-2397 SP - 324 EP - 327 PB - IEEE ER - TY - JOUR A1 - Chen, Rui A1 - Song, Ruizhou A1 - Zhang, Zhuo A1 - Bai, Long A1 - Liu, Fuqiang A1 - Jiang, Pei A1 - Sindersberger, Dirk A1 - Monkman, Gareth J. A1 - Guo, Jianglong T1 - Bio-Inspired Shape-Adaptive Soft Robotic Grippers Augmented with Electroadhesion Functionality JF - Soft Robotics N2 - Soft robotic grippers (SRGs) have been extensively employed in robotic grasping and manipulation applications due to the fact that they are beneficial for pick-and-place of difficult-to-handle and delicate objects with various geometries and stiffness in a comfortable and safer way. This article presents a bio-inspired and shape-adaptive SRG augmented with electroadhesion (EA) functionality, FinEA, by a cost-effective combination of a Fin Ray structured two-fingered SRG with two soft-stretchable EA pads. The EA pads were manufactured by screen printing a layer of electrically conductive and elastomeric carbon black powder mixed with polydimethylsiloxane onto a dielectric substrate. The compliant Fin Ray fingers, composed of soft longitudinal beams and rigid cross beams, were structurally optimized by the finite element method using ABAQUS/CAE based on three key parameters: the open angle of the longitudinal beams, the spacing between the cross beams, and the incline angle of the cross beams. The soft beams were produced by a traditional soft lithography method, whereas the rigid cross beams were three-dimensionally printed. The resultant FinEA grippers were capable of lifting not only flat/thin materials without distorting them due to the employment of EA, but also concave and convex objects due to the passively shape-adaptive Fin Ray structure and the EA functionality. In addition, the proposed FinEA grippers were able to grasp delicate materials and objects whose diameters are larger than the overall gripper length. Furthermore, 65% more weight in shear were picked up by the FinEA gripper when 4 kV was applied compared with 0 V. The FinEA concept provides useful and alternative solution for controllable adhesion-based SRGs and may facilitate the inspiration and development of future SRGs with added functionality and enhanced versatility. KW - electroadhesion KW - Fin Ray structure KW - shape-adaptive KW - soft robotic grippers Y1 - 2019 U6 - https://doi.org/10.1089/soro.2018.0120 VL - 6 IS - 6 SP - 701 EP - 712 PB - Mary Ann Liebert ER - TY - JOUR A1 - Diermeier, Andreas A1 - Sindersberger, Dirk A1 - Angele, Peter A1 - Kujat, Richard A1 - Monkman, Gareth J. T1 - Sensor system for use with low intensity pulsed ultrasound JF - Sensor review N2 - Purpose Ultrasound is a well-established technology in medical science, though many of the conventional measurement systems (hydrophones and radiation force balances [RFBs]) often lack accuracy and tend to be expensive. This is a significant problem where sensors must be considered to be "disposable" because they inevitably come into contact with biological fluids and expense increases dramatically in cases where a large number of sensors in array form are required. This is inevitably the case where ultrasound is to be used for the in vitro growth stimulation of a large plurality of biological samples in tissue engineering. Traditionally only a single excitation frequency is used (typically 1.5 MHz), but future research demands a larger choice of wavelengths for which a single broadband measurement transducer is desirable. Furthermore, because of implementation conditions there can also be large discrepancies between measurements. The purpose of this paper deals with a very cost-effective alternative to expensive RFBs and hydrophones. Design/methodology/approach Utilization of cost-effective piezoelectric elements as broadband sensors. Findings Very effective results with equivalent (if not better) accuracy than expensive alternatives. Originality/value This paper concentrates on how very cost-effective piezoelectric ultrasound transducers can be implemented as sensors for ultrasound power measurements with accuracy as good, if not better than those achievable using radiation force balances or hydrophones. KW - BALANCE KW - Hydrophone KW - Mesenchymal stem cell KW - Piezoelectric transducer KW - Radiation force balance KW - Sensors KW - therapy KW - Tissue engineering KW - Ultrasound Y1 - 2019 U6 - https://doi.org/10.1108/SR-11-2018-0304 SN - 0260-2288 VL - 39 IS - 6 SP - 828 EP - 834 PB - Emerald ER - TY - JOUR A1 - Sindersberger, Dirk A1 - Prem, Nina A1 - Monkman, Gareth J. T1 - Self-assembling structure formation in low-density magnetoactive polymers JF - Journal of Applied Polymer Science N2 - The formation of microstructures in magnetoactive polymers (MAPs) is a recently discovered phenomenon found only with very low filler particle concentrations (less than 3 wt %). Due to the degassing process, filler particles collect around an ascending bubble, which dissolves at a certain point leaving particulate rings within the matrix. The formation of toroidal microstructures commences as filler concentration approaches 1 wt %. The development of coherent parallel aligned rings with a compact order continues as particle concentrations increase toward 2 wt %. Between 2 and 3 wt % capillary doublets develop, while mass percentages higher than 3% result in increasing entropy as the random order of particle agglomeration found in higher concentration MAP dominates. Self-structured samples of different filler material and concentrations between 1 and 3 wt % have been investigated using X-ray tomography, where the emerging structures can be observed and visualized. The ring structures resulting from this research represent microinductivities which can be fabricated in a targeted manner, thus enabling new applications in the high-frequency radio field. Furthermore, these anisotropic, but well-organized, structures have magnetic field-dependent implications for optical, thermal, acoustic, and medical applications. KW - composites KW - ELASTOMERS KW - magnetism and magnetic properties KW - Particle KW - PERMEABILITY KW - self-assembly KW - sensors and actuators KW - VISCOELASTIC PROPERTIES KW - X-ray Y1 - 2019 U6 - https://doi.org/10.1002/app.48291 VL - 137 IS - 3 PB - Wiley ER - TY - JOUR A1 - Sorokin, Vladislav V. A1 - Stepanov, Gennady V. A1 - Shamonin (Chamonine), Mikhail A1 - Monkman, Gareth J. A1 - Kramarenko, Elena Yu T1 - Magnetorheological behavior of magnetoactive elastomers filled with bimodal iron and magnetite particles JF - Smart materials and structures N2 - Magnetoactive elastomers (MAE) based on soft silicone matrices, filled with various proportions of large diameter ( approximately 50 mu m) iron and small diameter ( approximately 0.5 mu m) magnetite particles are synthesized. Their rheological behavior in homogeneous magnetic fields up to 600 mT is studied in detail. The addition of small magnetite particles facilitates fabrication of uniformly distributed magnetic elastomer composites by preventing aggregation and sedimentation of large particles during curing. It is shown that using the proposed bimodal filler particles it is possible to tailor various magnetorheological (MR) properties which can be useful for different target applications. In particular, either absolute or relative magnetorheological effects can be tuned. The value of the damping factor as well as the range of deformation amplitudes for the linear viscoelastic regime can be chosen. The interdependencies between different MR properties of bimodal MAEs are considered. The results are discussed in the model framework of particle network formation under the simultaneous influence of external magnetic fields and mechanical deformation. KW - damping factor KW - DAMPING PROPERTIES KW - FIELD KW - HYDROGELS KW - MAGNETOELASTIC BEHAVIOR KW - Magnetorheological effect KW - magnetorheological elastomer KW - mechanical hysteresis KW - Payne effect Y1 - 2017 U6 - https://doi.org/10.1088/1361-665X/26/3/035019 VL - 26 IS - 3 PB - IOP Publishing ER - TY - JOUR A1 - Stoll, Andrea A1 - Mayer, Matthias A1 - Monkman, Gareth J. A1 - Shamonin (Chamonine), Mikhail T1 - Evaluation of highly compliant magneto-active elastomers with colossal magnetorheological response JF - Journal of applied polymer science N2 - Highly compliant elastomers with a shear storage modulus as low as 25 Pa are prepared using commercially available silicone, plasticizer, and tactile mutator silicone additive. They are used as matrix material for magneto-active elastomers (MAEs) with carbonyl iron contents between 0 and 85 wt %. In the absence of an external magnetic field, the storage modulus of MAEs based on two selected mixtures ranges between ~100 Pa and ~2000 Pa. Addition of a mutator to the matrix mixture results in a long post-cure period depending on the curing temperature and the initial mixture. In the presence of a magnetic field, the presented MAEs exhibit a strong magneto-induced change in storage modulus resulting in a colossal magnetorheological effect of >106 % which is ~30 times higher than previously reported values. The results are of interest in applications using such elastomers as cell substrates with magnetically tunable rigidity. Y1 - 2014 U6 - https://doi.org/10.1002/app.39793 SN - 1097-4628 SN - 0021-8995 PB - Wiley CY - New York, NY ER - TY - JOUR A1 - Monkman, Gareth J. T1 - Advances in Shape Memory Polymer Actuation JF - Mechatronics N2 - Shape memory materials fulfill an important role in both actuation and mechanical coupling between actuators and associated dynamic systems. The simplest techniques are thermally based and in addition to the more common shape memory alloys there are also shape memory polymers. These have similar characteristics to those of their metallic cousins, but there the relationship stops. The basic physical principles are very different and this paper attempts to outline the current state-of-the-art to those already involved with the technology and perhaps open a fresh chapter in smart materials to those who are new to it. Y1 - 2000 U6 - https://doi.org/10.1016/S0957-4158(99)00068-9 SN - 1873-4006 SN - 0957-4158 VL - 10 IS - 4/5 SP - 489 EP - 498 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Monkman, Gareth J. T1 - Precise Piezoelectric Prehension JF - Industrial Robot N2 - Piezoelectric actuators are well established for use in expensive optical equipment. Within the last decade, relatively inexpensive piezoelectric actuators have become established technology in pneumatic switching and the first piezoelectrically driven impactive robot grippers are just starting to emerge. Although this article concentrates largely on the use of piezoelectric actuators for use in robot gripping systems, the potential for applications outside this field is immense. KW - Piezoelectric actuators KW - Robots KW - Grippers KW - Nanotechnology Y1 - 2000 U6 - https://doi.org/10.1108/01439910010371605 SN - 0143-991x VL - 27 IS - 3 SP - 189 EP - 194 PB - MCB University Press ER - TY - JOUR A1 - Monkman, Gareth J. T1 - Workpiece Retention during Machine Processing JF - Assembly Automation N2 - Discusses the failings of conventional fixturing systems such as jigs and clamps and describes how electrorheological fluids can be used for flexible fixturing and workpiece retention. KW - Grippers KW - Rheology Y1 - 2001 U6 - https://doi.org/10.1108/01445150110381754 SN - 1758-4078 SN - 0144-5154 VL - 21 IS - 1 SP - 61 EP - 67 PB - Emerald CY - Bringley ER - TY - CHAP A1 - Kreitmeier, Florian A1 - Schulz, Irene A1 - Monkman, Gareth J. A1 - Shamonin (Chamonine), Mikhail A1 - Fetisov, Yuri K. A1 - Chashin, Dmitri V. A1 - Fetisov, Leonid Y. T1 - Observation of Nonlinear Magnetoelectric Response to Magnetic Pulses in Layered Magnetostrictive-Piezoelectric Structures N2 - A detailed experimental study of the magnetoelectric response of planar bi- and symmetric trilayer composite structures to magnetic field pulses is reported. The structures consist of layers of commercially available piezoelectric (lead zirconate titanate) and magnetostrictive (permendur or nickel) materials. The magnetic-field pulses have the form of a half-wave sine function with duration of 450 μs and amplitude from 500 Oe up to 38 kOe. The measurement method is explained and the measured time dependence of the resulting voltage is presented. The most interesting case, when pulse amplitudes are sufficiently large (~ 1-10 kOe) and various types of acoustic oscillation with frequencies much larger than the reciprocal pulse length are excited in the structures, is considered. The dependencies of the magnetoelectric voltage coefficient on the excitation frequency and the applied magnetic field are calculated. By digital signal processing the results are compared with those obtained by the method of harmonic field modulation (HFM). The findings are of interest for developing magnetoelectric sensors for pulsed magnetic fields as well as for rapid characterization of magnetoelectric composite structures. T2 - Proceedings of 2012 21st IEEE ISAF held jointly with 11th IEEE ECAPD and IEEE PFM (ISAF/ECAPD/PFM), 9th-13th of July 2012, Aveiro, Portugal KW - composite materials KW - magnetoelectric effect KW - magnetoelectric sensors KW - magnetostriction KW - piezoelectricity KW - magnetic field pulse Y1 - 2012 U6 - https://doi.org/10.1109/ISAF.2012.6297739 PB - IEEE ER - TY - CHAP A1 - Petchartee, Somrak A1 - Monkman, Gareth J. T1 - Contact Identification using Tactile Arrays T2 - Proceedings of the 7th IEEE International Symposium on Signal Processing and Information Technology (ISSPIT 2007), 15.-18.12.2007, Giza, Egypt N2 - The proposed method allows a robot to quantify tactile recognition of grasped objects. The responses by the robot are matched by randomly introducing objects following the completion of tactile sensor based training phases on 4 specific objects. The reproduction of the robotic contact identification is accomplished by matching threshold values of the smallest eigenvalue of the Quadric surface - called the eigenvalue trajectory. Once the grasped objects are introduced to the 2-fingered robot hand, the eigenvalue trajectory of contact surfaces are calculated by the system. Calculations are based on the degree of similarity of the characteristics between the newly received and previously trained tactile data. Experimental results indicate that the proposed algorithm allows a successful quantification of robotic contact recognition and the accomplishment of high levels of accuracy in contact identification. These results confirm that the proposed method is useful for identifying contact surfaces based on tactile sensor data. KW - Touch recognition KW - contact classification KW - tactile sensor Y1 - 2007 U6 - https://doi.org/10.1109/ISSPIT.2007.4458144 SP - 1121 EP - 1126 PB - IEEE ER - TY - CHAP A1 - Petchartee, Somrak A1 - Monkman, Gareth J. T1 - Contact Classification using Tactile Arrays T2 - 2007 3rd International Conference on Intelligent Sensors, Sensor Networks and Information (ISSNIP), 3, 03.-06.12.2007, Melbourne, VIC, Australia N2 - This paper proposed a contact recognition algorithm capable of determining contact surfaces types by tactile sensor fusion. This algorithm can recognize grasped objects using a 2- fingered robot hand, on which tactile sensors are mounted. Experiments have demonstrated reliable surface classification and accurate transformation independent of object shape and orientation. The contribution of this paper regards the relations between a surface and the points cloud defining it. Particularly, we investigate on the possibility that there is some intrinsic feature of a points cloud under quadric surface, allowing us to discriminate or classify a dataset defining a surface from the acquisition noise. KW - manipulators KW - objec recognition KW - sensor arrays KW - signal classification KW - tactile sensors Y1 - 2007 U6 - https://doi.org/10.1109/ISSNIP.2007.4496848 SP - 227 EP - 232 ER - TY - JOUR A1 - Petchartee, Somrak A1 - Monkman, Gareth J. T1 - Optimisation of Prehension Force through Tactile Sensing JF - Journal of Advanced Manufacturing Technology Y1 - 2007 SN - 2289-8107 PB - Universiti Teknikal Malaysia Melaka ER - TY - JOUR A1 - Prem, Nina A1 - Chavez Vega, Jhohan Harvey A1 - Böhm, Valter A1 - Sindersberger, Dirk A1 - Monkman, Gareth J. A1 - Zimmermann, Klaus T1 - Properties of Polydimethylsiloxane and Magnetoactive Polymers with Electroconductive Particles JF - Macromolecular Chemistry and Physics N2 - Magnetoactive polymers are intelligent materials whose mechanical and electrical characteristics are reversibly influenced by external magnetic stimuli. They consist of a highly elastic polymer matrix in which magnetically soft and/or hard particles are distributed by means of special fabrication processes. In addition to ferromagnetic particles such as carbonyl iron powder, electrically conductive particles may also be embedded into the polymer matrix. After characterizing a range of compounds, this work focuses on a comparison of the electrical properties and the suitability of various materials for applications, with particular emphasis on integration into 3D and 6D printing processes. 6D printing is based on the selective positioning of particles in a 3D polymer matrix with a further three degrees of freedom for a graduated dispersion of the particles at certain points and in desired directions. The aim is therefore to ensure that the polymers containing electroconductive tracks have the best possible electrical properties, that is, low resistivity but are still capable of being printed. A comparison between the traditionally used compounds containing graphite and carbon black is made for the first time. This latter is found to be greatly superior both in terms of electrical conductivity and applicability to 3D printing and 6D printing. KW - 3D printing KW - 6D printing KW - carbon black KW - composites KW - electroconductive particles KW - graphite KW - magnetoactive polymers KW - polydimethylsiloxane KW - STRAIN, *MRU Y1 - 2018 U6 - https://doi.org/10.1002/macp.201800222 VL - 219 IS - 18 PB - Wiley ER - TY - JOUR A1 - Bartsch, Alexander A1 - Beham, Daniela A1 - Gebhardt, Jakob A1 - Ehrlich, Ingo A1 - Schratzenstaller, Thomas A1 - Monkman, Gareth J. T1 - Mechanical Properties of NdPrFeB Based Magnetoactive Bisphenol-Free Boron-Silicate Polymers JF - Journal of Nanomedicine and Nanotechnology N2 - Following a ban on many materials containing bisphenol-A, new bisphenol-free Boron silicates have been found as substitutes. The purpose of this study is to describe the mechanical properties of these bisphenol-free magnetoactive borosilicate polymers containing hard magnetic particles. Samples of 0%, 33% and 66% by wt. were loaded for compression using a universal testing machine. The maximum forces occurring for different travel speeds were compared before and after post-magnetization treatments. The post-magnetization included 2 stages. In addition, the change in mechanical properties within 24 hours after the post-magnetization process was investigated. Furthermore, the influence of speed and particle content were investigated. In general, there is a correlation between the required compressive force and, the level of post-magnetization stress, the increase in travel speed and particle content in the boron silicate. Comparison of the non-post-magnetized and post-magnetized samples using two-tailed t-tests shows that the p-values for all weight fraction changes in NdPrFeB particles and travel speeds are less than 0.001. Also, a comparison between tests in which the traverse speed was varied also showed significant changes in the resulting compression forces. The same is valid for changes in the weight ratio of the NdPrFeB particles in the samples. For post-magnetized samples, no significant difference can be observed in the first 24 hours following magnetization. In summary, the material presents viscoelastic, plastic force-displacement behavior, which can be well recognized by its bi-linear curve shape. The investigation shows that borosilicate polymers based on NdPrFeB can have their mechanical behavior modified and controlled by post-magnetization processes. This opens new possibilities for many future applications. Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-67425 UR - https://www.walshmedicalmedia.com/open-access/mechanical-properties-of-ndprfeb-based-magnetoactive-bisphenolfree-boronsilicate-polymers-124385.html SN - 2157-7439 N1 - Corresponding author: Alexander Bartsch VL - 14 IS - 6 PB - Walsh Medical Media ER - TY - JOUR A1 - Knörzer, S. A1 - Hiller, Karl-Anton A1 - Brandt, M. A1 - Niklas, Andreas A1 - Putzger, Jürgen A1 - Monkman, Gareth J. A1 - Danilov, Sergey N. A1 - Ganichev, Sergey D. A1 - Schulz, Irene A1 - Schmalz, Gottfried T1 - Detection of pulsed blood flow through a molar pulp chamber and surrounding tissue in vitro JF - Journal of Clinical Oral Investigations N2 - OBJECTIVES Due to severe limitations of dental pulp sensitivity tests, the direct recording of pulsed blood flow, using photoplethysmography (PPG), has been proposed. In vivo evaluation is methodologically difficult and in vitro models have hitherto been adversely influenced by shortcomings in emulating the in vivo situation. Consequently, the aim of this study was to test an improved data acquisition system and to use this configuration for recording pulsed blood in a new model. MATERIALS AND METHODS We introduced a PPG signal detection system by recording signals under different blood flow conditions at two wavelengths (625 and 940 nm). Pulsed blood flow signals were measured using an in vitro model, containing a molar with a glass pulp and a resin socket, which closely resembled in vivo conditions with regard to volumetric blood flow, pulp anatomy, and surrounding tissue. RESULTS The detection system showed improved signal strength without stronger blanketing of noise. On the tooth surface, it was possible to detect signals emanating from pulsed blood flow from the glass pulp and from surrounding tissue at 625 nm. At 940 nm, pulp derived signals were recorded, without interference signals from surrounding tissue. CONCLUSION The PPG-based method has the potential to detect pulsed blood flow in small volumes in the pulp and (at 625 nm) also in adjacent tissues. CLINICAL RELEVANCE The results show the need for clear differentiation of the spatial origins of blood flow signals of any vitality test method to be applied to teeth. KW - Dental Pulp KW - Dental Pulp Cavity KW - Dental Pulp Test KW - Laser-Doppler Flowmetry KW - Molar Y1 - 2019 U6 - https://doi.org/10.1007/s00784-018-2530-y VL - 23 IS - 3 SP - 1121 EP - 1132 PB - Springer Nature ER - TY - JOUR A1 - Zimmermann, Klaus A1 - Böhm, Valter A1 - Becker T.I., A1 - Chavez Vega, Jhohan Harvey A1 - Kaufhold, Tobias A1 - Monkman, Gareth J. A1 - Sindersberger, Dirk A1 - Diermeier, Andreas A1 - Prem, Nina T1 - Mechanical Characterization of the Field-Dependent Properties of Magnetoactive Polymers and Integrated Electrets for their Application in Soft Robotics JF - International Scientific Journal "Problems of Mechanics" Y1 - 2017 SN - 1512-0740 VL - 69 IS - 4 ER - TY - JOUR A1 - Lang, Alexander A1 - Monkman, Gareth J. T1 - An analysis of the electrical capacitance between two conducting spheres JF - Journal of Electrostatics N2 - Many modern composites consist of dielectric polymer matrices containing embedded spherical particles. These particles can be electrically conducting and often have magnetic properties. In order to accurately model and simulate such materials, precise calculation of the electrical capacitance between identically sized spheres is required. This is of particular relevance at microscopic dimensions where many smart material-based micro devices are concerned. This may appear trivial for a small number of particles. However, many methods or their analysis appear to be questionable or not applicable at reduced dimensions. In this work, the various methods of analysis are scrutinized before being compared with both simulation and direct measurements. It is surprising to note that of the many works investigated only 3 are in close agreement with both simulation and measurement. Graphical abstract This paper deals with the precise calculation of the electrical capacitance between two conducting spheres of equal, or near equal size.The calculations have been verified by both experimental measurements and simulation. Algorithms in MatLab (Octave) format have been included in the supporting information. KW - Capacitance between spheres KW - Calculation KW - Simulation Experiment Y1 - 2020 U6 - https://doi.org/10.1016/j.elstat.2020.103518 VL - 108 PB - Elsevier ER - TY - JOUR A1 - Metsch, P. A1 - Schmidt, Henrik A1 - Sindersberger, Dirk A1 - Kalina, K. A. A1 - Brummund, J. A1 - Auernhammer, Günter A1 - Monkman, Gareth J. A1 - Kästner, Markus T1 - Field-Induced Interactions in Magneto-Active Elastomers BT - A Comparison of Experiments and Simulations JF - Smart Materials and Structures N2 - In this contribution, field-induced interactions of magnetizable particles embedded into a soft elastomer matrix are analyzed with regard to the resulting mechanical deformations. By comparing experiments for two-, three- and four-particle systems with the results of finite element simulations, a fully coupled continuum model for magneto-active elastomers is validated with the help of real data for the first time. The model under consideration permits the investigation of magneto-active elastomers with arbitrary particle distances, shapes and volume fractions as well as magnetic and mechanical properties of the individual constituents. It thus represents a basis for future studies on more complex, realistic systems. Our results show a very good agreement between experiments and numerical simulations—the deformation behavior of all systems is captured by the model qualitatively as well as quantitatively. Within a sensitivity analysis, the influence of the initial particle positions on the systems' response is examined. Furthermore, a comparison of the full three-dimensional model with the often used, simplified two-dimensional approach shows the typical overestimation of resulting interactions in magneto-active elastomers. Y1 - 2020 U6 - https://doi.org/10.1088/1361-665X/ab92dc N1 - Corrigendum: Field-induced interactions in magneto-active elastomers—a comparison of experiments and simulations (2020 Smart Mater. Struct. 29 085026); https://doi.org/10.1088/1361-665X/abb98b VL - 29 IS - 8 SP - 1 EP - 10 PB - IOPscience ER - TY - JOUR A1 - Zimmermann, Klaus A1 - Chavez Vega, Jhohan Harvey A1 - Becker, Tatiana I. A1 - Witte, Hartmut A1 - Schilling, Cornelius A1 - Köhring, Sebastian A1 - Böhm, Valter A1 - Monkman, Gareth J. A1 - Prem, Nina A1 - Sindersberger, Dirk A1 - Lutz, I. I. A1 - Merker, Lukas T1 - An approach to a form-adaptive compliant gripper element based on magneto-sensitive elastomers with a bioinspired sensorized surface JF - Problems of Mechanics Y1 - 2019 SN - 1512-0740 VL - 75 IS - 2 SP - 23 EP - 38 PB - Georgian Technical University CY - Tbilisi ER - TY - CHAP A1 - Drexler, C. A1 - Hirmer, Marion A1 - Danilov, Sergey N. A1 - Giglberger, Stephan A1 - Putzger, Jürgen A1 - Niklas, Andreas A1 - Jäger, Andreas A1 - Hiller, Karl-Anton A1 - Löffler, S. A1 - Schmalz, Gottfried A1 - Redlich, Britta A1 - Schulz, Irene A1 - Monkman, Gareth J. A1 - Ganichev, Sergey D. T1 - Infrared spectroscopy for clinical diagnosis of dental pulp vitality T2 - 37th International Conference on Infrared, Millimetre, and Terahertz Waves (IRMMW-THz 37), 23-28 September 2012 , Wollongong, Australia N2 - Transmission spectra of wet human teeth and dentin slices, together with blood of different flow rates were investigated over a wide spectral range, from visible to terahertz (THz) light. The results make it possible to find the optimum light frequency for an all-optical determination of pulpal blood flow and, consequently, for clinically diagnosis of tooth vitality. Y1 - 2012 U6 - https://doi.org/10.1109/IRMMW-THz.2012.6380091 PB - IEEE CY - Piscataway, NJ ER - TY - JOUR A1 - Dillinger, Andrea Elisabeth A1 - Weber, Gregor R. A1 - Mayer, Matthias A1 - Schneider, Magdalena A1 - Göppner, Corinna A1 - Ohlmann, Andreas A1 - Shamonin (Chamonine), Mikhail A1 - Monkman, Gareth J. A1 - Fuchshofer, Rudolf A1 - Keller, Kate A1 - Lozano, Diana C. A1 - Clark, Abbot T1 - CCN2/CTGF-A Modulator of the Optic Nerve Head Astrocyte JF - Frontiers in cell and developmental biology (Front Cell Dev Biol.) N2 - In primary open-angle glaucoma (POAG), a neurodegenerative disease of the optic nerve (ON) and leading cause of blindness, the optic nerve head (ONH) undergoes marked structural extracellular matrix (ECM) changes, which contribute to its permanent deformation and to degeneration of ON axons. The remodeling process of the ECM causes changes in the biomechanical properties of the ONH and the peripapillary sclera, which is accompanied by an increased reactivity of the resident astrocytes. The molecular factors involved in the remodeling process belong to the Transforming growth factor (TGF)-β superfamily, especially TGF-β2. In previous publications we showed that TGF-β2 induced ECM alterations are mediated by Cellular Communication Network Factor (CCN)2/Connective Tissue Growth Factor (CTGF) and recently we showed that CCN2/CTGF is expressed by astrocytes of the ON under normal conditions. In this study we wanted to get a better understanding of the function of CCN2/CTGF under normal and pathologic conditions. To this end, we analyzed the glial lamina and peripapillary sclera of CCN2/CTGF overexpressing mice and studied the effect of CCN2/CTGF and increasing substratum stiffness on murine ON astrocytes in vitro. We observed enhanced astrocyte reactivity in the ONH, increased ECM protein synthesis in the peripapillary sclera and increased Ccn2/Ctgf expression in the ONH during the pathologic development in situ. CCN2/CTGF treatment of primary murine ON astrocytes induced a higher migration rate, and increase of ECM proteins including fibronectin, elastin and collagen type III. Furthermore, the astrocytes responded to stiffer substratum with increased glial fibrillary acidic protein, vimentin, actin and CCN2/CTGF synthesis. Finally, we observed the reinforced appearance of CCN2/CTGF in the lamina cribrosa of glaucomatous patients. We conclude that reactive changes in ONH astrocytes, induced by the altered biomechanical characteristics of the region, give rise to a self-amplifying process that includes increased TGF-β2/CCN2/CTGF signaling and leads to the synthesis of ECM molecules and cytoskeleton proteins, a process that in turn augments the stiffness at the ONH. Such a scenario may finally result in a vicious circle in the pathogenesis of POAG. The transgenic CTGF-overexpressing mouse model might be an optimal model to study the chronic pathological POAG changes in the ONH. KW - astrocytes KW - extracellar matrix KW - glaucoma KW - glial lamina KW - growth factors KW - optic nerve KW - stiffness Y1 - 2022 U6 - https://doi.org/10.3389/fcell.2022.864433 VL - 10 PB - frontiers ER - TY - JOUR A1 - Putz, Christoph A1 - Schirmer, Maximilian A1 - Sattler, Robert A1 - Monkman, Gareth J. T1 - Fabrication of Bisphenol-free Boron-Siloxane Polymers JF - Materials Chemistry and Physics N2 - Interest in the preparation of magnetoactive boron-siloxane polymers (MBP) has been stimulated by recent scientific developments. However, recent regulations have prohibited the inclusion of Bisphenol-A normally employed in the manufacture of commercially available products. In the following publication, two different routes for the preparation of magnetoactive borosiloxane polymers have been taken. First, the possibilities of obtaining homogeneous mixtures of magnetoactive polymers by mixing the magnetic particles with the polymer using solid CO2 (dry ice) and stirring (shearing) are investigated. In the course of the work, an approach for the preparation of reference materials of different viscosities was made to prove the transferability to other elastomers. This is then followed by a brief review of the reaction of the polymer with different solvents in relation to the mixing with particles. In manually kneaded compounds, dispersions ranging from 0.00004 to 0.004 particles per mm3 are common. The process described in this work resulted in agglomerations of no greater than 0.00004 particles per mm3 A possible synthesis route for bisphenol-free boron-siloxanes is then considered, in which for the polymer matrix, polydimethylsilanes (dichloro(methyl)silane), boric acid and iron(III)chloride are used for this purpose by polycondensation. Y1 - 2025 U6 - https://doi.org/10.1016/j.matchemphys.2025.130567 N1 - Corresponding author der OTH Regensburg: Gareth J. Monkman PB - Elsevier ET - Journal Pre-proof ER -