@article{MonkmanSindersbergerPremetal., author = {Monkman, Gareth J. and Sindersberger, Dirk and Prem, Nina and Szecsey, Tamara}, title = {Smart Stiction}, series = {Robotics \& Automation Engineering Journal}, volume = {4}, journal = {Robotics \& Automation Engineering Journal}, number = {4}, publisher = {Juniper Publishers}, doi = {10.19080/RAEJ.2019.04.555641}, abstract = {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.}, language = {en} } @article{SindersbergerPremMonkman, author = {Sindersberger, Dirk and Prem, Nina and Monkman, Gareth J.}, title = {Structure formation in low concentration magnetoactive polymers}, series = {AIP advances}, volume = {9}, journal = {AIP advances}, number = {3}, publisher = {AIP Publishing}, doi = {10.1063/1.5079997}, abstract = {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).}, language = {en} } @article{PremSindersbergerMonkman, author = {Prem, Nina and Sindersberger, Dirk and Monkman, Gareth J.}, title = {Mini-Extruder for 3D Magnetoactive Polymer Printing}, series = {Advances in Materials Science and Engineering}, journal = {Advances in Materials Science and Engineering}, publisher = {HINDAWI}, doi = {10.1155/2019/8715718}, pages = {1 -- 8}, abstract = {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.}, language = {en} } @article{MonkmanSindersbergerPrem, author = {Monkman, Gareth J. and Sindersberger, Dirk and Prem, Nina}, title = {Magnetically enhanced photoconductive high voltage control}, series = {ISSS Journal of Micro and Smart Systems}, volume = {11}, journal = {ISSS Journal of Micro and Smart Systems}, publisher = {Springer Nature}, doi = {10.1007/s41683-021-00088-z}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-30606}, pages = {317 -- 328}, abstract = {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.}, language = {en} } @article{MonkmanSindersbergerPremetal., author = {Monkman, Gareth J. and Sindersberger, Dirk and Prem, Nina and Diermeier, Andreas and Szecsey, Tamara}, title = {Dielectric behaviour of magnetic hybrid materials}, series = {Physical Sciences Reviews}, volume = {7}, journal = {Physical Sciences Reviews}, number = {10}, publisher = {de Gruyter}, doi = {10.1515/psr-2019-0121}, pages = {1169 -- 1185}, abstract = {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.}, language = {en} } @article{PremSindersbergerStriegletal., author = {Prem, Nina and Sindersberger, Dirk and Striegl, Birgit and B{\"o}hm, Valter and Monkman, Gareth J.}, title = {Shape memory effects using magnetoactive Boron-organo-silicon oxide polymers}, series = {Macromolecular Chemistry and Physics}, volume = {221}, journal = {Macromolecular Chemistry and Physics}, number = {15}, publisher = {Wiley}, doi = {10.1002/macp.202000149}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-23205}, pages = {1 -- 8}, abstract = {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.}, language = {en} } @article{MonkmanStrieglPremetal., author = {Monkman, Gareth J. and Striegl, Birgit and Prem, Nina and Sindersberger, Dirk}, title = {Electrical Properties of Magnetoactive Boron-Organo-Silicon Oxide Polymers}, series = {Macromolecular Chemistry and Physics}, volume = {221}, journal = {Macromolecular Chemistry and Physics}, number = {4}, publisher = {Wiley}, doi = {10.1002/macp.201900342}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-26488}, pages = {1 -- 8}, abstract = {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.}, language = {en} } @article{PremSindersbergerMonkman, author = {Prem, Nina and Sindersberger, Dirk and Monkman, Gareth J.}, title = {Infrared spectral analysis of low concentration magnetoactive polymers}, series = {Journal of Applied Polymer Science}, volume = {137}, journal = {Journal of Applied Polymer Science}, number = {7}, publisher = {Wiley}, organization = {WILEY}, issn = {1097-4628}, doi = {10.1002/app.48366}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-25913}, pages = {1 -- 7}, abstract = {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.}, language = {en} }