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Keywords = stretchable membranes

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12 pages, 2510 KiB  
Article
Nanofibrous Membrane-Based Stretchable Electrochemical Sweat Sensor for pH Detection
by Longzhou Zhang, Baoyuan Ma, Zhiguang Xu and Yan Zhao
Polymers 2025, 17(5), 663; https://doi.org/10.3390/polym17050663 - 28 Feb 2025
Cited by 1 | Viewed by 801
Abstract
Wearable, non-invasive sweat sensors capable of continuously monitoring the pH of sweat, which is a key indicator related to metabolism and homeostasis level, are highly desirable for personal health management. However, ensuring the stability and accuracy of these sensors can be challenging when [...] Read more.
Wearable, non-invasive sweat sensors capable of continuously monitoring the pH of sweat, which is a key indicator related to metabolism and homeostasis level, are highly desirable for personal health management. However, ensuring the stability and accuracy of these sensors can be challenging when the body is in motion. In this work, we prepared a stretchable nanofibrous membrane-based electrochemical pH-sensing electrode by embedding carbon nanotubes (MWCNT) and silver nanowires (AgNWs) into an elastic electrospun nanofibrous membrane, followed by polyaniline electrodeposition. The as-prepared pH-sensing electrode showed a high sensitivity of 82.53 mV/pH and high accuracy in ionic solutions with pH ranging from 3 to 7. Notably, the electrode maintained stable sensing performance under deformations, including torsion, bending, and tensile strains up to 30%. Even after 1000 cycles of stretching at a 30% tensile strain, the detection sensitivity remained above 70 mV/pH, indicating its potential application as a wearable electrochemical sensor for monitoring sweat pH in personal health management. Full article
(This article belongs to the Special Issue Biomaterials Modification, Characterization and Applications)
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19 pages, 15802 KiB  
Article
Preparation and Characterization of Highly Conductive PVDF/PAN Conjugate Electrospun Fibrous Membranes with Embedded Silver Nanoparticles
by Siyang Wu, Luyu Zhang, Xiaochun Qiu, Yuntai Guo, Liangliang Dong, Mingzhuo Guo and Jiale Zhao
Polymers 2024, 16(24), 3540; https://doi.org/10.3390/polym16243540 - 19 Dec 2024
Cited by 1 | Viewed by 1216
Abstract
This study reports the development of highly conductive and stretchable fibrous membranes based on PVDF/PAN conjugate electrospinning with embedded silver nanoparticles (AgNPs) for wearable sensing applications. The fabrication process integrated conjugate electrospinning of PVDF/PAN, selective dissolution of polyvinylpyrrolidone (PVP) to create porous networks, [...] Read more.
This study reports the development of highly conductive and stretchable fibrous membranes based on PVDF/PAN conjugate electrospinning with embedded silver nanoparticles (AgNPs) for wearable sensing applications. The fabrication process integrated conjugate electrospinning of PVDF/PAN, selective dissolution of polyvinylpyrrolidone (PVP) to create porous networks, and uniform AgNP incorporation via adsorption-reduction. Systematic optimization revealed that 10 wt.% PVP content and 1.2 mol/L AgNO3 concentration yielded membranes with superior electrical conductivity (874.93 S/m) and mechanical strength (2.34 MPa). The membranes demonstrated excellent strain sensing performance with a gauge factor of 12.64 within 0–30% strain and location-specific sensing capabilities: moderate movements at wrist (ΔR/R0: 98.90–287.25%), elbow (124.65–300.24%), and fingers (177.01–483.20%) generated stable signals, while knee articulation exhibited higher sensitivity (459.60–1316.48%) but significant signal fluctuations. These results demonstrate the potential of the developed conductive porous PVDF/PAN composite fibrous membranes for applications in wearable sensors, flexible electronics, and human-machine interfaces, particularly in scenarios requiring moderate-range motion detection with high reliability and stability. The findings suggest promising opportunities for developing next-generation wearable sensing devices through the optimization of conjugate electrospun fibrous membranes. Full article
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16 pages, 6470 KiB  
Article
Mechanical Behavior of Lithium-Ion Battery Separators under Uniaxial and Biaxial Loading Conditions
by Sahand Shamchi, Behzad V. Farahani, Marian Bulla and Stefan Kolling
Polymers 2024, 16(8), 1174; https://doi.org/10.3390/polym16081174 - 22 Apr 2024
Cited by 2 | Viewed by 3067
Abstract
The mechanical integrity of two commercially available lithium-ion battery separators was investigated under uniaxial and biaxial loading conditions. Two dry-processed microporous films with polypropylene (PP)/polyethylene (PE)/polypropylene (PP) compositions were studied: Celgard H2010 Trilayer and Celgard Q20S1HX Ceramic-Coated Trilayer. The uniaxial tests were carried [...] Read more.
The mechanical integrity of two commercially available lithium-ion battery separators was investigated under uniaxial and biaxial loading conditions. Two dry-processed microporous films with polypropylene (PP)/polyethylene (PE)/polypropylene (PP) compositions were studied: Celgard H2010 Trilayer and Celgard Q20S1HX Ceramic-Coated Trilayer. The uniaxial tests were carried out along the machine direction (MD), transverse direction (TD), and diagonal direction (DD). In order to generate a state of in-plane biaxial tension, a pneumatic bulge test setup was prioritized over the commonly performed punch test in an attempt to eliminate the effects of contact friction. The biaxial flow stress–strain behavior of the membranes was deduced via the Panknin–Kruglov method coupled with a 3D Digital Image Correlation (DIC) technique. The findings demonstrate a high degree of in-plane anisotropy in both membranes. The ceramic coating was found to negatively affect the mechanical performance of the trilayer microporous separator, compromising its strength and stretchability, while preserving its failure mode. Derived from experimentally calibrated constitutive models, a finite element model was developed using the explicit solver OpenRadioss. The numerical model was capable of predicting the biaxial deformation of the semicrystalline membranes up until failure, showing a fairly good correlation with the experimental observations. Full article
(This article belongs to the Special Issue Crystalline Polymer Materials for Soft Electronics)
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10 pages, 6909 KiB  
Communication
Highly Stretchable Thermoplastic Polyurethane Separators for Li-Ion Batteries Based on Non-Solvent-Induced Phase Separation Method
by Tae Hyung Kim, MinSu Kim, Eun Ji Kim, Minu Ju, Ji Soo Kim and Seung Hee Lee
Polymers 2024, 16(3), 357; https://doi.org/10.3390/polym16030357 - 29 Jan 2024
Cited by 2 | Viewed by 3063
Abstract
The growing interest in wearable and portable devices has stimulated the need for flexible and stretchable lithium-ion batteries (LiBs). A crucial component in these batteries is the separator, which provides a pathway for Li-ion transfer and prevents electrode contact. In a flexible and [...] Read more.
The growing interest in wearable and portable devices has stimulated the need for flexible and stretchable lithium-ion batteries (LiBs). A crucial component in these batteries is the separator, which provides a pathway for Li-ion transfer and prevents electrode contact. In a flexible and stretchable LiB, the separator must exhibit stretchability and elasticity akin to its existing counterparts. Here, we developed a non-modified thermoplastic polyurethane (TPU) separator using the non-solvent induced phase separation (NIPS) technique. We compared their performance with commercially available polypropylene (PP) separators. Our results demonstrate that TPU separators exhibit superior elasticity based on repeated stretch/release tests with excellent thermal stability and electrolyte wettability. Furthermore, our findings confirm that TPU separators, even after being repeatedly stretched and released, can function effectively without severe damage in a fabricated coin cell LiB with high oxidative stability, as evidenced by linear sweep voltammetry, like commercially available separators. Full article
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14 pages, 7593 KiB  
Article
Fabrication and Performance Evaluation of a Cation Exchange Membrane Using Graphene Oxide/Polyethersulfone Composite Nanofibers
by Suhun Kim, Abayomi Babatunde Alayande, Tasnim Eisa, Jaewon Jang, Yesol Kang, Euntae Yang, Moon-Hyun Hwang, In S. Kim and Kyu-Jung Chae
Membranes 2023, 13(7), 633; https://doi.org/10.3390/membranes13070633 - 29 Jun 2023
Cited by 3 | Viewed by 2812
Abstract
Ion exchange membranes, especially cation exchange membranes (CEMs), are an important component in membrane-based energy generation and storage because of their ability to transport cations via the electrochemical potential gradient while preventing electron transport. However, developing a CEM with low areal resistance, high [...] Read more.
Ion exchange membranes, especially cation exchange membranes (CEMs), are an important component in membrane-based energy generation and storage because of their ability to transport cations via the electrochemical potential gradient while preventing electron transport. However, developing a CEM with low areal resistance, high permselectivity, and stability remains difficult. In this study, electrospun graphene oxide/polyethersulfone (GO/PES) composite nanofibers were prepared with varying concentrations of GO. To fabricate a CEM, the pores of the electrospun GO/PES nanofiber substrates were filled with a Nafion ionomer. The pore-filled PES nanofiber loaded with 1% GO revealed a noticeable improvement in hydrophilicity, structural morphology, and mechanical properties. The 1% GO/PES pore-filled CEM was compared to a Nafion membrane of a varying thickness and without a nanofiber substrate. The CEM with a nanofiber substrate showed permselectivity of 85.75%, toughness of 111 J/m3, and areal resistance of 3.7 Ω cm2, which were 12.8%, 4.3 times, and 4.0 times better, respectively, than those of the Nafion membrane at the same thickness. The development of a reinforced concrete-like GO/PES nanofiber structure containing stretchable ionomer-enhanced membrane surfaces exhibited suitable areal resistance and reduced the thickness of the composite membrane without compromising the mechanical strength, suggesting its potential application as a cation exchange membrane in electrochemical membrane-based systems. Full article
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12 pages, 3845 KiB  
Article
An Intelligent Glove of Synergistically Enhanced ZnO/PAN-Based Piezoelectric Sensors for Diversified Human–Machine Interaction Applications
by Min Wang, Xiaojuan Hou, Shuo Qian, Shuai Xian, Junbin Yu, Jian He and Xiujian Chou
Electronics 2023, 12(8), 1782; https://doi.org/10.3390/electronics12081782 - 10 Apr 2023
Cited by 8 | Viewed by 2354
Abstract
Human–machine interaction is now deeply integrated into our daily lives. However, the rigidity and high-power supply of traditional devices limit their further development. Herein, a high-performance flexible piezoelectric sensor (HFPS) based on a novel zinc oxide/polyacrylonitrile/Ecoflex (ZnO/PAN/Ecoflex) composite membrane is proposed. Due to [...] Read more.
Human–machine interaction is now deeply integrated into our daily lives. However, the rigidity and high-power supply of traditional devices limit their further development. Herein, a high-performance flexible piezoelectric sensor (HFPS) based on a novel zinc oxide/polyacrylonitrile/Ecoflex (ZnO/PAN/Ecoflex) composite membrane is proposed. Due to the synergistic piezoelectricity of ZnO and PAN, the output voltage/current of the HFPS is increased by 140%/100% compared to the pure Zno/Ecoflex composite membrane. Furthermore, the fabricated HFPSs also have excellent sensitivity, linearity, stability and flexibility under periodic pressure. On this basis, due to its flexibility, stretchability and battery-free characteristics, a self-powered HFPS-based intelligent glove is proposed to wirelessly control diverse electronic systems through human hand gestures. In the meanwhile, the intelligent glove has been successfully applied to car two-dimensional motion, light bulb control and fan control. With the advantages of simple operation, portability and low power consumption, the glove is expected to provide new application prospects for human–machine interaction systems. Full article
(This article belongs to the Special Issue Flexible Electronics: Sensors, Energy and Health)
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12 pages, 6972 KiB  
Article
Highly Stretchable and Robust Electrochemical Sensor Based on 3D Graphene Oxide–CNT Composite for Detecting Ammonium in Sweat
by Yunzhi Hua, Mingxiang Guan, Linzhong Xia, Yu Chen, Junhao Mai, Cong Zhao and Changrui Liao
Biosensors 2023, 13(3), 409; https://doi.org/10.3390/bios13030409 - 21 Mar 2023
Cited by 9 | Viewed by 3556
Abstract
Wearable electrochemical sensors have attracted tremendous attention and have been experiencing rapid growth in recent years. Sweat, one of the most suitable biological fluids for non-invasive monitoring, contains various chemical elements relating abundant information about human health conditions. In this work, a new [...] Read more.
Wearable electrochemical sensors have attracted tremendous attention and have been experiencing rapid growth in recent years. Sweat, one of the most suitable biological fluids for non-invasive monitoring, contains various chemical elements relating abundant information about human health conditions. In this work, a new type of non-invasive and highly stretchable potentiometric sweat sensor was developed based on all-solid-state ion-selective electrode (ISE) coupled with poly(dimethylsiloxane; PDMS) and polyurethane (PU). This highly stretchable composite of PDMS-PU allows the sensor to be robust, with the PDMS providing a flexible backbone and the PU enhancing the adhesion between the electrodes and the substrate. In addition, graphene–carbon nanotube (CNT) network 3D nanomaterials were introduced to modify the ion selective membrane (ISM) in order to increase the charge transfer activity of the ISEs, which also could minimize the formation of water layers on the electrode surface, as such nanomaterials are highly hydrophobic. As a result, the sensor demonstrated a wide detection range of NH4+ from 10−6 M to 10−1 M with high stability and sensitivity—showing a high sensitivity of 59.6 ± 1.5 mV/log [NH4+] and an LOD lower than 10−6 M. Under a strain of 40%, the sensor still showed a sensitivity of 42.7 ± 3.1 mV/log [NH4+]. The proposed highly stretchable and robust electrochemical sweat sensor provides a new choice for wearable-device-based personal daily healthcare management beyond hospital-centric healthcare monitoring. Full article
(This article belongs to the Special Issue Advances in Wearable Biosensors for Healthcare Monitoring)
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8 pages, 2197 KiB  
Article
A Stretchable Expanded Polytetrafluorethylene-Silicone Elastomer Composite Electret for Wearable Sensor
by Jianbo Tan, Kaikai Chen, Jinzhan Cheng, Zhaoqin Song, Jiahui Zhang, Shaodi Zheng, Zisheng Xu and Shiju E
Nanomaterials 2023, 13(1), 158; https://doi.org/10.3390/nano13010158 - 29 Dec 2022
Cited by 5 | Viewed by 2510
Abstract
Soaring developments in wearable electronics raise an urgent need for stretchable electrets. However, achieving soft electrets simultaneously possessing excellent stretchability, longevity, and high charge density is still challenging. Herein, a facile approach is proposed to prepare an all-polymer hybrid composite electret based on [...] Read more.
Soaring developments in wearable electronics raise an urgent need for stretchable electrets. However, achieving soft electrets simultaneously possessing excellent stretchability, longevity, and high charge density is still challenging. Herein, a facile approach is proposed to prepare an all-polymer hybrid composite electret based on the coupling of elastomer and ePTFE membrane. The composite electrets are fabricated via a facile casting and thermal curing process. The obtained soft composite electrets exhibit constantly high surface potential (−0.38 kV) over a long time (30 days), large strain (450%), low hysteresis, and excellent durability (15,000 cycles). To demonstrate the applications, the stretchable electret is utilized to assemble a self-powered flexible sensor based on the electrostatic induction effect for the monitoring of human activities. Additionally, output signals in the pressure mode almost two orders of magnitude larger than those in the strain mode are observed and the sensing mechanism in each mode is investigated. Full article
(This article belongs to the Special Issue Nanotechnology for Energy Generation and Storage)
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16 pages, 3806 KiB  
Article
A Novel In Vitro Wound Healing Assay Using Free-Standing, Ultra-Thin PDMS Membranes
by Karya Uysal, Ipek Seda Firat, Till Creutz, Inci Cansu Aydin, Gerhard M. Artmann, Nicole Teusch and Aysegül Temiz Artmann
Membranes 2023, 13(1), 22; https://doi.org/10.3390/membranes13010022 - 24 Dec 2022
Cited by 3 | Viewed by 3232
Abstract
Advances in polymer science have significantly increased polymer applications in life sciences. We report the use of free-standing, ultra-thin polydimethylsiloxane (PDMS) membranes, called CellDrum, as cell culture substrates for an in vitro wound model. Dermal fibroblast monolayers from 28- and 88-year-old donors were [...] Read more.
Advances in polymer science have significantly increased polymer applications in life sciences. We report the use of free-standing, ultra-thin polydimethylsiloxane (PDMS) membranes, called CellDrum, as cell culture substrates for an in vitro wound model. Dermal fibroblast monolayers from 28- and 88-year-old donors were cultured on CellDrums. By using stainless steel balls, circular cell-free areas were created in the cell layer (wounding). Sinusoidal strain of 1 Hz, 5% strain, was applied to membranes for 30 min in 4 sessions. The gap circumference and closure rate of un-stretched samples (controls) and stretched samples were monitored over 4 days to investigate the effects of donor age and mechanical strain on wound closure. A significant decrease in gap circumference and an increase in gap closure rate were observed in trained samples from younger donors and control samples from older donors. In contrast, a significant decrease in gap closure rate and an increase in wound circumference were observed in the trained samples from older donors. Through these results, we propose the model of a cell monolayer on stretchable CellDrums as a practical tool for wound healing research. The combination of biomechanical cell loading in conjunction with analyses such as gene/protein expression seems promising beyond the scope published here. Full article
(This article belongs to the Special Issue Latest Scientific Discoveries in Polymer Membranes)
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12 pages, 3141 KiB  
Article
Comparative Study on Preparation Methods for Transparent Conductive Films Based on Silver Nanowires
by Jizhe Zhang, Xingzhong Zhu, Juan Xu, Ruixing Xu, Hao Yang and Caixia Kan
Molecules 2022, 27(24), 8907; https://doi.org/10.3390/molecules27248907 - 14 Dec 2022
Cited by 7 | Viewed by 2831
Abstract
Silver nanowires, which have high optoelectronic properties, have the potential to supersede indium tin oxide in the field of electrocatalysis, stretchable electronic, and solar cells. Herein, four mainstream experimental methods, including Mayer–rod coating, spin coating, spray coating, and vacuum filtration methods, are employed [...] Read more.
Silver nanowires, which have high optoelectronic properties, have the potential to supersede indium tin oxide in the field of electrocatalysis, stretchable electronic, and solar cells. Herein, four mainstream experimental methods, including Mayer–rod coating, spin coating, spray coating, and vacuum filtration methods, are employed to fabricate transparent conductive films based on the same silver nanowires to clarify the significance of preparation methods on the performance of the films. The surface morphology, conductive property, uniformity, and flexible stability of these four Ag NW-based films, are analyzed and compared to explore the advantages of these methods. The transparent conductive films produced by the vacuum filtration method have the most outstanding performance in terms of surface roughness and uniformity, benefitting from the stronger welding of NW-NW junctions after the press procedure. However, limited by the size of the membrane and the vacuum degree of the equipment, the small-size Ag films used in precious devices are appropriate to obtain through this method. Similarly, the spin coating method is suited to prepare Ag NWs films with small sizes, which shows excellent stability after the bending test. In comparison, much larger-size films could be obtained through Mayer-rod coating and spray coating methods. The pull-down speed and force among the Mayer-rod coating process, as well as the spray distance and traveling speed among the spray coating process, are essential to the uniformity of Ag NW films. After being treated with NaBH4 and polymethyl methacrylate (PMMA), the obtained Ag NW/PMMA films show great potential in the field of film defogging due to the Joule heating effect. Taken together, based on the advantages of each preparation method, the Ag NW-based films with desired size and performances are easier to prepare, meeting the requirements of different application fields. Full article
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18 pages, 8014 KiB  
Article
MetaMembranes for the Sensitivity Enhancement of Wearable Piezoelectric MetaSensors
by Saman Farhangdoust, Gary Georgeson and Jeong-Beom Ihn
Sensors 2022, 22(5), 1909; https://doi.org/10.3390/s22051909 - 1 Mar 2022
Cited by 7 | Viewed by 2886
Abstract
The low stretchability of plain membranes restricts the sensitivity of conventional diaphragm-based pressure and inflatable piezoelectric sensors. Using theoretical and computational tools, we characterized current limitations and explored metamaterial-inspired membranes (MetaMems) to resolve these issues. This paper develops two MetaMem pressure sensors (MPSs) [...] Read more.
The low stretchability of plain membranes restricts the sensitivity of conventional diaphragm-based pressure and inflatable piezoelectric sensors. Using theoretical and computational tools, we characterized current limitations and explored metamaterial-inspired membranes (MetaMems) to resolve these issues. This paper develops two MetaMem pressure sensors (MPSs) to enrich the sensitivity and stretchability of the conventional sensors. Two auxetic hexagonal and kirigami honeycombs are proposed to create a negative Poisson’s ratio (NPR) in the MetaMems which enables them to expand the piezo-element of sensors in both longitudinal and transverse directions much better, and consequently provides the MPSs’ diaphragm a higher capability for flexural deformation. Polyvinylidene fluoride (PVDF) and polycarbonate (PC) are considered as the preferable materials for the piezo-element and MetaMem, respectively. A finite element analysis was conducted to investigate the stretchability behavior of the MetaMems and study its effect on the PVDF’s polarization and sensor sensitivity. The results obtained from theoretical analysis and numerical simulations demonstrate that the proposed MetaMems enhance the sensitivity of pressure sensors up to 3.8 times more than an equivalent conventional sensor with a plain membrane. This paper introduces a new class of flexible MetaMems to advance wearable piezoelectric metasensor technologies. Full article
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18 pages, 1071 KiB  
Article
Baseline Stiffness Modulates the Non-Linear Response to Stretch of the Extracellular Matrix in Pulmonary Fibrosis
by Constança Júnior, Maria Narciso, Esther Marhuenda, Isaac Almendros, Ramon Farré, Daniel Navajas, Jorge Otero and Núria Gavara
Int. J. Mol. Sci. 2021, 22(23), 12928; https://doi.org/10.3390/ijms222312928 - 29 Nov 2021
Cited by 21 | Viewed by 4338
Abstract
Pulmonary fibrosis (PF) is a progressive disease that disrupts the mechanical homeostasis of the lung extracellular matrix (ECM). These effects are particularly relevant in the lung context, given the dynamic nature of cyclic stretch that the ECM is continuously subjected to during breathing. [...] Read more.
Pulmonary fibrosis (PF) is a progressive disease that disrupts the mechanical homeostasis of the lung extracellular matrix (ECM). These effects are particularly relevant in the lung context, given the dynamic nature of cyclic stretch that the ECM is continuously subjected to during breathing. This work uses an in vivo model of pulmonary fibrosis to characterize the macro- and micromechanical properties of lung ECM subjected to stretch. To that aim, we have compared the micromechanical properties of fibrotic ECM in baseline and under stretch conditions, using a novel combination of Atomic Force Microscopy (AFM) and a stretchable membrane-based chip. At the macroscale, fibrotic ECM displayed strain-hardening, with a stiffness one order of magnitude higher than its healthy counterpart. Conversely, at the microscale, we found a switch in the stretch-induced mechanical behaviour of the lung ECM from strain-hardening at physiological ECM stiffnesses to strain-softening at fibrotic ECM stiffnesses. Similarly, we observed solidification of healthy ECM versus fluidization of fibrotic ECM in response to stretch. Our results suggest that the mechanical behaviour of fibrotic ECM under stretch involves a potential built-in mechanotransduction mechanism that may slow down the progression of PF by steering resident fibroblasts away from a pro-fibrotic profile. Full article
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12 pages, 2664 KiB  
Article
An Electret/Hydrogel-Based Tactile Sensor Boosted by Micro-Patterned and Electrostatic Promoting Methods with Flexibility and Wide-Temperature Tolerance
by Zhensheng Chen, Jiahao Yu, Haozhe Zeng, Zhao Chen, Kai Tao, Jin Wu and Yunjia Li
Micromachines 2021, 12(12), 1462; https://doi.org/10.3390/mi12121462 - 27 Nov 2021
Cited by 12 | Viewed by 3408
Abstract
With the rising demand for wearable, multifunctional, and flexible electronics, plenty of efforts aiming at wearable devices have been devoted to designing sensors with greater efficiency, wide environment tolerance, and good sustainability. Herein, a thin film of double-network ionic hydrogel with a solution [...] Read more.
With the rising demand for wearable, multifunctional, and flexible electronics, plenty of efforts aiming at wearable devices have been devoted to designing sensors with greater efficiency, wide environment tolerance, and good sustainability. Herein, a thin film of double-network ionic hydrogel with a solution replacement treatment method is fabricated, which not only possesses excellent stretchability (>1100%) and good transparency (>80%), but also maintains a wide application temperature range (−10~40 °C). Moreover, the hydrogel membrane further acts as both the flexible electrode and a triboelectric layer, with a larger friction area achieved through a micro-structure pattern method. Combining this with a corona-charged fluorinated ethylene propylene (FEP) film, an electret/hydrogel-based tactile sensor (EHTS) is designed and fabricated. The output performance of the EHTS is effectively boosted by 156.3% through the hybrid of triboelectric and electrostatic effects, which achieves the open-circuit peak voltage of 12.5 V, short-circuit current of 0.5 μA, and considerable power of 4.3 μW respectively, with a mentionable size of 10 mm × 10 mm × 0.9 mm. The EHTS also demonstrates a stable output characteristic within a wide range of temperature tolerance from −10 to approximately 40 °C and can be further integrated into a mask for human breath monitoring, which could provide for a reliable healthcare service during the COVID-19 pandemic. In general, the EHTS shows excellent potential in the fields of healthcare devices and wearable electronics. Full article
(This article belongs to the Special Issue Smart Devices and Systems for Vibration Sensing and Energy Harvesting)
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12 pages, 2211 KiB  
Article
An Ultra-Sensitive Multi-Functional Optical Micro/Nanofiber Based on Stretchable Encapsulation
by Siheng Xiang, Hui You, Xinxiang Miao, Longfei Niu, Caizhen Yao, Yilan Jiang and Guorui Zhou
Sensors 2021, 21(22), 7437; https://doi.org/10.3390/s21227437 - 9 Nov 2021
Cited by 14 | Viewed by 2985
Abstract
Stretchable optical fiber sensors (SOFSs), which are promising and ultra-sensitive next-generation sensors, have achieved prominent success in applications including health monitoring, robotics, and biological–electronic interfaces. Here, we report an ultra-sensitive multi-functional optical micro/nanofiber embedded with a flexible polydimethylsiloxane (PDMS) membrane, which is compatible [...] Read more.
Stretchable optical fiber sensors (SOFSs), which are promising and ultra-sensitive next-generation sensors, have achieved prominent success in applications including health monitoring, robotics, and biological–electronic interfaces. Here, we report an ultra-sensitive multi-functional optical micro/nanofiber embedded with a flexible polydimethylsiloxane (PDMS) membrane, which is compatible with wearable optical sensors. Based on the effect of a strong evanescent field, the as-fabricated SOFS is highly sensitive to strain, achieving high sensitivity with a peak gauge factor of 450. In addition, considering the large negative thermo-optic coefficient of PDMS, temperature measurements in the range of 30 to 60 °C were realized, resulting in a 0.02 dBm/°C response. In addition, wide-range detection of humidity was demonstrated by a peak sensitivity of 0.5 dB/% RH, with less than 10% variation at each humidity stage. The robust sensing performance, together with the flexibility, enables the real-time monitoring of pulse, body temperature, and respiration. This as-fabricated SOFS provides significant potential for the practical application of wearable healthcare sensors. Full article
(This article belongs to the Special Issue Micro-/Nano-Fiber Sensors and Optical Integration Devices)
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17 pages, 4768 KiB  
Article
Mechanical Stretching-Induced Traumatic Brain Injury Is Mediated by the Formation of GSK-3β-Tau Complex to Impair Insulin Signaling Transduction
by Pei-Wen Cheng, Yi-Chung Wu, Tzyy-Yue Wong, Gwo-Ching Sun and Ching-Jiunn Tseng
Biomedicines 2021, 9(11), 1650; https://doi.org/10.3390/biomedicines9111650 - 9 Nov 2021
Cited by 2 | Viewed by 3854
Abstract
Traumatic brain injury confers a significant and growing public health burden. It is a major environmental risk factor for dementia. Nonetheless, the mechanism by which primary mechanical injury leads to neurodegeneration and an increased risk of dementia-related diseases is unclear. Thus, we aimed [...] Read more.
Traumatic brain injury confers a significant and growing public health burden. It is a major environmental risk factor for dementia. Nonetheless, the mechanism by which primary mechanical injury leads to neurodegeneration and an increased risk of dementia-related diseases is unclear. Thus, we aimed to investigate the effect of stretching on SH-SY5Y neuroblastoma cells that proliferate in vitro. These cells retain the dopamine-β-hydroxylase activity, thus being suitable for neuromechanistic studies. SH-SY5Y cells were cultured on stretchable membranes. The culture conditions contained two groups, namely non-stretched (control) and stretched. They were subjected to cyclic stretching (6 and 24 h) and 25% elongation at 1 Hz. Following stretching at 25% and 1 Hz for 6 h, the mechanical injury changed the mitochondrial membrane potential and triggered oxidative DNA damage at 24 h. Stretching decreased the level of brain-derived neurotrophic factors and increased amyloid-β, thus indicating neuronal stress. Moreover, the mechanical injury downregulated the insulin pathway and upregulated glycogen synthase kinase 3β (GSK-3β)S9/p-Tau protein levels, which caused a neuronal injury. Following 6 and 24 h of stretching, GSK-3βS9 was directly bound to p-TauS396. In contrast, the neuronal injury was improved using GSK-3β inhibitor TWS119, which downregulated amyloid-β/p-Taus396 phosphorylation by enhancing ERK1/2T202/Y204 and AktS473 phosphorylation. Our findings imply that the neurons were under stress and that the inactivation of the GSK3β could alleviate this defect. Full article
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