TY - JOUR A1 - Wang, Bei A1 - Corsi, Cosimo A1 - Weiland, Thomas A1 - Wang, Zhenyu A1 - Grund, Thomas A1 - Pohl, Olaf A1 - Bienia, Johannes Max A1 - Weiss, Julien A1 - Ngo, Ha Duong ED - Dai, Ching-Liang ED - Tsai, Yao-Chuan ED - Dai, Zhi-Xuan T1 - Screen-Printed PVDF Piezoelectric Pressure Transducer for Unsteadiness Study of Oblique Shock Wave Boundary Layer Interaction JF - Micromachines N2 - Shock wave boundary/layer interactions (SWBLIs) are critical in high-speed aerodynamic flows, particularly within supersonic regimes, where unsteady dynamics can induce structural fatigue and degrade vehicle performance. Conventional measurement techniques, such as pressure-sensitive paint (PSP), face limitations in frequency response, calibration complexity, and intrusive instrumentation. Similarly, MEMS-based sensors, like Kulite ® sensors, present challenges in terms of intrusiveness, cost, and integration complexity. This study presents a flexible, lightweight polyvinylidene fluoride (PVDF) piezoelectric sensor array designed for high-resolution wall-pressure measurements in SWBLI research. The primary objective is to optimize low-frequency pressure fluctuation detection, addressing SWBLI’s need for accurate, real-time measurements of low-frequency unsteadiness. Fabricated using a double-sided screen-printing technique, this sensor array is low-cost, flexible, and provides stable, high-sensitivity data. Finite Element Method (FEM) simulations indicate that the sensor structure also has potential for high-frequency responses, behaving as a high-pass filter with minimal signal attenuation up to 300 kHz, although the current study’s experimental testing is focused on low-frequency calibration and validation. A custom low-frequency sound pressure setup was used to calibrate the PVDF sensor array, ensuring uniform pressure distribution across sensor elements. Wind tunnel tests at Mach 2 verified the PVDF sensor’s ability to capture pressure fluctuations and unsteady behaviors consistent with those recorded by Kulite sensors. The findings suggest that PVDF sensors are promising alternatives for capturing low-frequency disturbances and intricate flow structures in advanced aerodynamic research, with high-frequency performance to be further explored in future work. KW - Shock wave KW - supersonic KW - shock wave/boundary layer interaction (SWBLI) KW - PVDF KW - piezoelectric pressure transduce KW - FEM simulation KW - dynamic response in frequency domain KW - crosstalk effect KW - wall pressure KW - unsteadiness KW - PVDF Y1 - 2024 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:523-19411 SN - 2072-666X VL - 15 IS - 12 PB - MDPI ER - TY - JOUR A1 - Hubl, Moritz A1 - Atta, Raghied M. A1 - Kaufhold, Robin A1 - Wang, Bei A1 - Ngo, Ha Duong ED - Chronopoulou, Laura T1 - Nano-Materials-Based Printed Glucose Sensor for Use in Incontinence Products for Health-Care Applications JF - Micro N2 - Our recent development of a wireless humidity sensor system embedded in incontinence products enables new sensor applications to diagnose and supervise geriatric diseases (i.e., age-related diabetes mellitus type II). The measurement of glucose in urine, so-called glucosuria, is an early indicator for an incipient diabetes mellitus disease, whose symptoms are often age-related but misjudged. In this paper, an incontinence glucose sensor is printed with biocompatible ink and Prussian blue as an electron mediator on foil and functionalized with immobilized glucose oxidase. Inkjet printing of multiple layers of Nafion prevents large interference substances from diffusing into the measuring electrode and allows precise adjustment of the linear working range, which is significantly different from blood glucose measurement. Performance tests show the potential to detect minimum glucose values and store the sensor over a prolonged period at room temperature. The printed glucose sensor can be embedded into the absorber material of incontinence products, where capillary forces transport the urine analyte to the detection area. An attached readout module with an integrated potentiostat measures the glucose concentration in urine, which is transmitted wirelessly with incontinence events and stored in a cloud service for further analysis by medical staff and care workers. KW - Glucose-Sensor KW - printed glucose sensor KW - urine glucose sensor KW - printed electronics KW - Prussian blue mediator KW - electrochemic biosensor KW - glucosuria KW - diabetes mellitus KW - incontinence sensor KW - Polymerelektronik KW - Inkontinenz Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:523-18074 SN - 2673-8023 VL - 3 IS - 2 SP - 521 EP - 536 PB - MDPI ER - TY - JOUR A1 - Hubl, Moritz A1 - Atta, Raghied M. A1 - Kaufhold, Robin A1 - Wang, Bei A1 - Ngo, Ha Duong ED - Chronopoulou, Laura T1 - Nano-Materials-Based Printed Glucose Sensor for Use in Incontinence Products for Health-Care Applications JF - Micro N2 - Our recent development of a wireless humidity sensor system embedded in incontinence products enables new sensor applications to diagnose and supervise geriatric diseases (i.e., age-related diabetes mellitus type II). The measurement of glucose in urine, so-called glucosuria, is an early indicator for an incipient diabetes mellitus disease, whose symptoms are often age-related but misjudged. In this paper, an incontinence glucose sensor is printed with biocompatible ink and Prussian blue as an electron mediator on foil and functionalized with immobilized glucose oxidase. Inkjet printing of multiple layers of Nafion prevents large interference substances from diffusing into the measuring electrode and allows precise adjustment of the linear working range, which is significantly different from blood glucose measurement. Performance tests show the potential to detect minimum glucose values and store the sensor over a prolonged period at room temperature. The printed glucose sensor can be embedded into the absorber material of incontinence products, where capillary forces transport the urine analyte to the detection area. An attached readout module with an integrated potentiostat measures the glucose concentration in urine, which is transmitted wirelessly with incontinence events and stored in a cloud service for further analysis by medical staff and care workers. KW - Glucose KW - printed glucose sensor KW - urine glucose sensor KW - printed electronics KW - Prussian blue mediator KW - electrochemic biosensor KW - glucosuria KW - diabetes mellitus KW - incontinence sensor KW - Harn KW - 3D-Druck KW - Biosensor KW - Glucose-Sensor KW - Glucosurie KW - Diabetes mellitus KW - Harninkontinenz Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:523-17140 SN - 2673-8023 VL - 3 IS - 2 SP - 521 EP - 536 PB - MDPI ER - TY - JOUR A1 - Wang, Bei A1 - Sun, Ling A1 - Schneider-Ramelow, Martin A1 - Lang, Klaus-Dieter A1 - Ngo, Ha-Duong ED - Yang, Yi ED - Zhang, Yi ED - Xiao, Limin ED - El Abed, Abdel I. ED - Xiao, Shumin ED - Zhang, Xuming T1 - Recent Advances and Challenges of Nanomaterials-Based Hydrogen Sensors JF - Micromachines N2 - Safety is a crucial issue in hydrogen energy applications due to the unique properties of hydrogen. Accordingly, a suitable hydrogen sensor for leakage detection must have at least high sensitivity and selectivity, rapid response/recovery, low power consumption and stable functionality, which requires further improvements on the available hydrogen sensors. In recent years, the mature development of nanomaterials engineering technologies, which facilitate the synthesis and modification of various materials, has opened up many possibilities for improving hydrogen sensing performance. Current research of hydrogen detection sensors based on both conservational and innovative materials are introduced in this review. This work mainly focuses on three material categories, i.e., transition metals, metal oxide semiconductors, and graphene and its derivatives. Different hydrogen sensing mechanisms, such as resistive, capacitive, optical and surface acoustic wave-based sensors, are also presented, and their sensing performances and influence based on different nanostructures and material combinations are compared and discussed, respectively. This review is concluded with a brief outlook and future development trends. KW - Wasserstoff KW - hydrogen safety KW - hydrogen sensor KW - transition metals KW - catalytic sensing KW - micro and nanosensors KW - metal oxide semiconductors KW - graphene KW - graphene oxide KW - reduced graphene oxide KW - Mikrosensor KW - Graphen KW - Graphenoxid KW - Halbleiter Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:523-15302 SN - 2072-666X VL - 12 IS - 11 SP - 1 EP - 56 PB - MDPI ER - TY - JOUR A1 - Wang, Bei A1 - Baeuscher, Manuel A1 - Hu, Xiaodong A1 - Woehrmann, Markus A1 - Becker, Katharina A1 - Juergensen, Nils A1 - Hubl, Moritz A1 - Mackowiak, Piotr A1 - Schneider-Ramelow, Martin A1 - Lang, Klaus-Dieter A1 - Ngo, Ha-Duong T1 - Development and Characterization of a Novel Low-Cost Water-Level and Water Quality Monitoring Sensor by Using Enhanced Screen Printing Technology with PEDOT:PSS JF - Micromachines N2 - A novel capacitive sensor for measuring the water-level and monitoring the water quality has been developed in this work by using an enhanced screen printing technology. A commonly used environment-friendly conductive polymer poly(3,4-ethylenedioxythiophene):poly (styrenesulfonate) (PEDOT:PSS) for conductive sensors has a limited conductivity due to its high sheet resistance. A physical treatment performed during the printing process has reduced the sheet resistance of printed PEDOT:PSS on polyethylenterephthalat (PET) substrate from 264.39 Ω/sq to 23.44 Ω/sq. The adhesion bonding force between printed PEDOT:PSS and the substrate PET is increased by using chemical treatment and tested using a newly designed adhesive peeling force test. Using the economical conductive ink PEDOT:PSS with this new physical treatment, our capacitive sensors are cost-efficient and have a sensitivity of up to 1.25 pF/mm. KW - water-level sensor KW - water quality monitoring KW - adhesive peeling force test KW - screen printing KW - poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) KW - conductive polymer KW - capacitive sensor Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:523-3789 SN - 2072-666X VL - 11 IS - 5 PB - MDPI ER -