Pub Date : 2022-01-21DOI: 10.3389/felec.2021.762442
Maggie K. Delano, V. Ganapati, Rezhwan Kamal, Bryan D. Le, Jackie Le, Rey Mendoza
Fluid overload is a chronic medical condition that affects over six million Americans with conditions such as congestive heart failure, end-stage renal disease, and lymphedema. Remote management of fluid overload continues to be a leading clinical challenge. Bioimpedance is one technique that can be used to estimate the hydration of tissue and track it over time. However, commercially available bioimpedance measurement systems are bulky, expensive, and rely on Ag/AgCl electrodes that dry out and can irritate the skin. The use of bioimpedance today is therefore limited to clinical and research settings, with measurements performed at daily intervals or over short periods of time rather than continuously and long-term. This paper proposes using wearable calf bioimpedance measurements integrated into a compression sock for long-term fluid overload management. A PCB was developed using standard measurement techniques that measures the calf bioimpedance using a custom analog front-end built around an AD8302 gain-phase detection chip. Data is transmitted wirelessly via Bluetooth Low Energy to an iOS device using a custom iOS app. Bioimpedance data were collected both from the wearable system and a commercial measurement system (ImpediMed SFB7) using RRC networks, Ag/AgCl electrodes, and the textile compression sock. Bioimpedance data collected from the wearable system showed close agreement with data from the SFB7 when using RRC networks and in five healthy human subjects with Ag/AgCl electrodes. However, when using the textile compression sock the wearable system had worse precision than the SFB7 (4% run to run compared to < 1 % run to run) and there were larger differences between the two systems than when using the RRC networks and the Ag/AgCl electrodes. Wearable system precision and agreement with the SFB7 was improved by pressure or light wetting of the current electrodes on the sock. Future research should focus on reliable elimination of low-frequency artifacts in research grade hardware to enable long-term calf bioimpedance measurements for fluid overload management.
{"title":"Evaluating Research Grade Bioimpedance Hardware Using Textile Electrodes for Long-Term Fluid Status Monitoring","authors":"Maggie K. Delano, V. Ganapati, Rezhwan Kamal, Bryan D. Le, Jackie Le, Rey Mendoza","doi":"10.3389/felec.2021.762442","DOIUrl":"https://doi.org/10.3389/felec.2021.762442","url":null,"abstract":"Fluid overload is a chronic medical condition that affects over six million Americans with conditions such as congestive heart failure, end-stage renal disease, and lymphedema. Remote management of fluid overload continues to be a leading clinical challenge. Bioimpedance is one technique that can be used to estimate the hydration of tissue and track it over time. However, commercially available bioimpedance measurement systems are bulky, expensive, and rely on Ag/AgCl electrodes that dry out and can irritate the skin. The use of bioimpedance today is therefore limited to clinical and research settings, with measurements performed at daily intervals or over short periods of time rather than continuously and long-term. This paper proposes using wearable calf bioimpedance measurements integrated into a compression sock for long-term fluid overload management. A PCB was developed using standard measurement techniques that measures the calf bioimpedance using a custom analog front-end built around an AD8302 gain-phase detection chip. Data is transmitted wirelessly via Bluetooth Low Energy to an iOS device using a custom iOS app. Bioimpedance data were collected both from the wearable system and a commercial measurement system (ImpediMed SFB7) using RRC networks, Ag/AgCl electrodes, and the textile compression sock. Bioimpedance data collected from the wearable system showed close agreement with data from the SFB7 when using RRC networks and in five healthy human subjects with Ag/AgCl electrodes. However, when using the textile compression sock the wearable system had worse precision than the SFB7 (4% run to run compared to < 1 % run to run) and there were larger differences between the two systems than when using the RRC networks and the Ag/AgCl electrodes. Wearable system precision and agreement with the SFB7 was improved by pressure or light wetting of the current electrodes on the sock. Future research should focus on reliable elimination of low-frequency artifacts in research grade hardware to enable long-term calf bioimpedance measurements for fluid overload management.","PeriodicalId":73081,"journal":{"name":"Frontiers in electronics","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43778120","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-01-07DOI: 10.3389/felec.2021.804474
Sami Bolat, Evangelos Agiannis, Shih‐Chi Yang, Moritz H. Futscher, Abdesselam Aribia, I. Shorubalko, Y. Romanyuk
Solution processing and low-temperature annealing (T < 300°C) of the precursor compounds promise low-cost manufacturing for future applications of flexible oxide electronics. However, thermal budget reduction comes at the expense of increased charge trapping residuals in the dielectric layers, which result in hysteretic switching of transistors. This work reports on a novel bilayer dielectric scheme combining aluminum oxide (AlOx) as a positive charge trapping insulator and yttrium aluminum oxide (YAlOx) as a negative charge trapping dielectric to obtain hysteresis free switching in the solution-processed metal-oxide thin-film transistors. Devices were processed at a thermal budget of 250°C, without an encapsulation layer. The presence of H+ and OH− in the AlOx were found responsible for the hysteresis in the switching, which was suppressed successfully with the thickness optimization of the YAlOx in the dielectric stack. Fabricated devices yield ON/OFF ratios of 106, sub-pA level gate leakage currents, a subthreshold swing of 150 mV/decade, and field-effect mobility of 1.5 cm2/V-sec.
{"title":"Engineering Bilayer AlOx /YAlOx Dielectric Stacks for Hysteresis-Free Switching in Solution-Processed Metal-Oxide Thin-Film Transistors","authors":"Sami Bolat, Evangelos Agiannis, Shih‐Chi Yang, Moritz H. Futscher, Abdesselam Aribia, I. Shorubalko, Y. Romanyuk","doi":"10.3389/felec.2021.804474","DOIUrl":"https://doi.org/10.3389/felec.2021.804474","url":null,"abstract":"Solution processing and low-temperature annealing (T < 300°C) of the precursor compounds promise low-cost manufacturing for future applications of flexible oxide electronics. However, thermal budget reduction comes at the expense of increased charge trapping residuals in the dielectric layers, which result in hysteretic switching of transistors. This work reports on a novel bilayer dielectric scheme combining aluminum oxide (AlOx) as a positive charge trapping insulator and yttrium aluminum oxide (YAlOx) as a negative charge trapping dielectric to obtain hysteresis free switching in the solution-processed metal-oxide thin-film transistors. Devices were processed at a thermal budget of 250°C, without an encapsulation layer. The presence of H+ and OH− in the AlOx were found responsible for the hysteresis in the switching, which was suppressed successfully with the thickness optimization of the YAlOx in the dielectric stack. Fabricated devices yield ON/OFF ratios of 106, sub-pA level gate leakage currents, a subthreshold swing of 150 mV/decade, and field-effect mobility of 1.5 cm2/V-sec.","PeriodicalId":73081,"journal":{"name":"Frontiers in electronics","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42323618","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-01-06DOI: 10.3389/felec.2021.700363
Min Suk Lee, Akshay Paul, Yuchen Xu, W. Hairston, G. Cauwenberghs
With the rising need for on-body biometric sensing, the development of wearable electrophysiological sensors has been faster than ever. Surface electrodes placed on the skin need to be robust in order to measure biopotentials from the body reliably and comfortable for extended wearability. The electrical stability of nonpolarizable silver/silver chloride (Ag/AgCl) and its low-cost, commercial production have made these electrodes ubiquitous health sensors in the clinical environment, where wet gels and long wires are accommodated by patient immobility. However, smaller, dry electrodes with wireless acquisition are essential for truly wearable, continuous health sensing. Currently, techniques for the robust fabrication of custom Ag/AgCl electrodes are lacking. Here, we present three methods for the fabrication of Ag/AgCl electrodes: oxidizing Ag in a chlorine solution, electroplating Ag, and curing Ag/AgCl ink. Each of these methods is then used to create three different electrode shapes for wearable application. Bench-top and on-body evaluation of the electrode techniques was achieved by electrochemical impedance spectroscopy (EIS), calculation of variance in electrocardiogram (ECG) measurements, and analysis of auditory steady-state response (ASSR) measurement. Microstructures produced on the electrode by each fabrication technique were also investigated with scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The custom Ag/AgCl electrodes were found to be efficient in comparison with standard, commercial Ag/AgCl wet electrodes across all three of our presented techniques, with Ag/AgCl ink shown to be the better out of the three in bench-top and biometric recordings.
{"title":"Characterization of Ag/AgCl Dry Electrodes for Wearable Electrophysiological Sensing","authors":"Min Suk Lee, Akshay Paul, Yuchen Xu, W. Hairston, G. Cauwenberghs","doi":"10.3389/felec.2021.700363","DOIUrl":"https://doi.org/10.3389/felec.2021.700363","url":null,"abstract":"With the rising need for on-body biometric sensing, the development of wearable electrophysiological sensors has been faster than ever. Surface electrodes placed on the skin need to be robust in order to measure biopotentials from the body reliably and comfortable for extended wearability. The electrical stability of nonpolarizable silver/silver chloride (Ag/AgCl) and its low-cost, commercial production have made these electrodes ubiquitous health sensors in the clinical environment, where wet gels and long wires are accommodated by patient immobility. However, smaller, dry electrodes with wireless acquisition are essential for truly wearable, continuous health sensing. Currently, techniques for the robust fabrication of custom Ag/AgCl electrodes are lacking. Here, we present three methods for the fabrication of Ag/AgCl electrodes: oxidizing Ag in a chlorine solution, electroplating Ag, and curing Ag/AgCl ink. Each of these methods is then used to create three different electrode shapes for wearable application. Bench-top and on-body evaluation of the electrode techniques was achieved by electrochemical impedance spectroscopy (EIS), calculation of variance in electrocardiogram (ECG) measurements, and analysis of auditory steady-state response (ASSR) measurement. Microstructures produced on the electrode by each fabrication technique were also investigated with scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The custom Ag/AgCl electrodes were found to be efficient in comparison with standard, commercial Ag/AgCl wet electrodes across all three of our presented techniques, with Ag/AgCl ink shown to be the better out of the three in bench-top and biometric recordings.","PeriodicalId":73081,"journal":{"name":"Frontiers in electronics","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46777150","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-01-06DOI: 10.3389/felec.2021.786601
Federica Catania, Hugo de Souza Oliveira, M. C. Costa Angeli, M. Ciocca, S. Pané, N. Münzenrieder, G. Cantarella
Thin-film transistors (TFTs) based on amorphous indium-gallium-zinc-oxide (a-IGZO) have proved promising features for flexible and lightweight electronics. To achieve technological maturity for commercial and industrial applications, their stability under extreme environmental conditions is highly required. The combined effects of temperature (T) from −30.0°C to 50.0°C and relative humidity (RH) stress from 0 to 95% on a-IGZO TFT is presented. The TFT performances and the parameters variation were analysed in two different experiments. First, the TFT response was extracted while undergoing the most extreme climate conditions on Earth, ranging from the African Desert (50.0°C, 22%) to Antarctic (−30.0°C, 0%). Afterwards, the device functionality was demonstrated in three parts of the human body (forehand, arm and foot) at low (35%), medium (60%) and high (95%) relative humidity for on-skin and wearable applications. The sensitivity to T/RH variations suggests the suitability of these TFTs as sensing element for epidermal electronics and artificial skin.
{"title":"The Influence of Climate Conditions and On-Skin Positioning on InGaZnO Thin-Film Transistor Performance","authors":"Federica Catania, Hugo de Souza Oliveira, M. C. Costa Angeli, M. Ciocca, S. Pané, N. Münzenrieder, G. Cantarella","doi":"10.3389/felec.2021.786601","DOIUrl":"https://doi.org/10.3389/felec.2021.786601","url":null,"abstract":"Thin-film transistors (TFTs) based on amorphous indium-gallium-zinc-oxide (a-IGZO) have proved promising features for flexible and lightweight electronics. To achieve technological maturity for commercial and industrial applications, their stability under extreme environmental conditions is highly required. The combined effects of temperature (T) from −30.0°C to 50.0°C and relative humidity (RH) stress from 0 to 95% on a-IGZO TFT is presented. The TFT performances and the parameters variation were analysed in two different experiments. First, the TFT response was extracted while undergoing the most extreme climate conditions on Earth, ranging from the African Desert (50.0°C, 22%) to Antarctic (−30.0°C, 0%). Afterwards, the device functionality was demonstrated in three parts of the human body (forehand, arm and foot) at low (35%), medium (60%) and high (95%) relative humidity for on-skin and wearable applications. The sensitivity to T/RH variations suggests the suitability of these TFTs as sensing element for epidermal electronics and artificial skin.","PeriodicalId":73081,"journal":{"name":"Frontiers in electronics","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44795787","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-01-01DOI: 10.3389/felec.2022.824981
Shelby Critcher, Todd J Freeborn
Knee-focused wearable devices have the potential to support personalized rehabilitation therapies by monitoring localized tissue alterations related to activities that reduce functional symptoms and pain. However, supporting these applications requires reported data to be reliable and accurate which can be challenging in the unsupervised free-living conditions that wearable devices are deployed. This pilot study has assessed a knee-focused wearable sensor system to quantify 1) system performance (operation, rates of data artifacts, environment impacts) to estimate realistic targets for reliable data with this system and 2) user experiences (comfort, fit, usability) to help inform future designs to increase usability and adoption of knee-focused wearables. Study data was collected from five healthy adult participants over 2 days, with 84.5 and 35.9% of artifact free data for longitudinal and transverse electrode configurations. Small to moderate positive correlations were also identified between changes in resistance, temperature, and humidity with respect to acceleration to highlight how this system can be used to explore relationships between knee tissues and environmental/activity context.
{"title":"System Performance and User Feedback Regarding Wearable Bioimpedance System for Multi-Site Knee Tissue Monitoring: Free-Living Pilot Study With Healthy Adults.","authors":"Shelby Critcher, Todd J Freeborn","doi":"10.3389/felec.2022.824981","DOIUrl":"https://doi.org/10.3389/felec.2022.824981","url":null,"abstract":"<p><p>Knee-focused wearable devices have the potential to support personalized rehabilitation therapies by monitoring localized tissue alterations related to activities that reduce functional symptoms and pain. However, supporting these applications requires reported data to be reliable and accurate which can be challenging in the unsupervised free-living conditions that wearable devices are deployed. This pilot study has assessed a knee-focused wearable sensor system to quantify 1) system performance (operation, rates of data artifacts, environment impacts) to estimate realistic targets for reliable data with this system and 2) user experiences (comfort, fit, usability) to help inform future designs to increase usability and adoption of knee-focused wearables. Study data was collected from five healthy adult participants over 2 days, with 84.5 and 35.9% of artifact free data for longitudinal and transverse electrode configurations. Small to moderate positive correlations were also identified between changes in resistance, temperature, and humidity with respect to acceleration to highlight how this system can be used to explore relationships between knee tissues and environmental/activity context.</p>","PeriodicalId":73081,"journal":{"name":"Frontiers in electronics","volume":"3 ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10122869/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"9391111","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-12-24DOI: 10.3389/felec.2021.802356
Klara Mosshammer, Theresa Lüdke, Sarah Spitzner, Daniel Firzlaff, K. Harre, H. Kleemann, M. Neudert, T. Zahnert, K. Leo
Hypotension in the middle ear can cause serious diseases and hearing disorders. Until now, pressure in the middle ear is measured indirectly by using the impedance of the tympanic membrane (tympanometry). Direct methods are just described in scientific studies and would be harmful in clinical routine. Here, we demonstrate a bio-compatible pressure sensor, which can resolve pressure changes in the range of −7.5 kPa up to +7.5 kPa, and due to its compact design (area of 2 × 4 mm2), can be directly implanted in the human middle ear. Furthermore, the read-out of the pressure sensor can be conveniently done using wireless data communication technologies employing a plate capacitor with an elastic dielectric for pressure monitoring and a planar coil. Thus, our sensor allows for direct pressure measurements in the middle ear, avoiding additional surgeries after device implantation.
{"title":"Bio-Compatible Sensor for Middle Ear Pressure Monitoring on a Bio-Degradable Substrate","authors":"Klara Mosshammer, Theresa Lüdke, Sarah Spitzner, Daniel Firzlaff, K. Harre, H. Kleemann, M. Neudert, T. Zahnert, K. Leo","doi":"10.3389/felec.2021.802356","DOIUrl":"https://doi.org/10.3389/felec.2021.802356","url":null,"abstract":"Hypotension in the middle ear can cause serious diseases and hearing disorders. Until now, pressure in the middle ear is measured indirectly by using the impedance of the tympanic membrane (tympanometry). Direct methods are just described in scientific studies and would be harmful in clinical routine. Here, we demonstrate a bio-compatible pressure sensor, which can resolve pressure changes in the range of −7.5 kPa up to +7.5 kPa, and due to its compact design (area of 2 × 4 mm2), can be directly implanted in the human middle ear. Furthermore, the read-out of the pressure sensor can be conveniently done using wireless data communication technologies employing a plate capacitor with an elastic dielectric for pressure monitoring and a planar coil. Thus, our sensor allows for direct pressure measurements in the middle ear, avoiding additional surgeries after device implantation.","PeriodicalId":73081,"journal":{"name":"Frontiers in electronics","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-12-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49437263","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-12-10DOI: 10.3389/felec.2021.791016
M. A. Kadir, Adrian J. Wilson, K. Siddique-e Rabbani
Monitoring of anatomical structures and physiological processes by electrical impedance has attracted scientists as it is noninvasive, nonionizing and the instrumentation is relatively simple. Focused Impedance Method (FIM) is attractive in this context, as it has enhanced sensitivity at the central region directly beneath the electrode configuration minimizing contribution from neighboring regions. FIM essentially adds or averages two concentric and orthogonal combinations of conventional Tetrapolar Impedance Measurements (TPIM) and has three versions with 4, 6, and 8 electrodes. This paper describes the design and testing of a multi-frequency FIM (MFFIM) system capable of measuring all three versions of FIM at 8 frequencies in the range 10 kHz—1 MHz. A microcontroller based multi-frequency signal generator and a balanced Howland current source with high output impedance (476 kΩ at 10 kHz and 58.3 kΩ at 1 MHz) were implemented for driving currents into biological tissues with an error <1%. The measurements were carried out at each frequency sequentially. The peak values of the amplified voltage signals were measured using a novel analogue synchronous peak detection technique from which the transfer impedances were obtained. The developed system was tested using TPIM measurements on a passive RC Cole network placed between two RC networks, the latter representing skin-electrode contact impedances. Overall accuracy of the measurement was very good (error <4% at all frequencies except 1 MHz, with error 6%) and the resolution was 0.1 Ω. The designed MFFIM system had a sampling rate of >45 frames per second which was deemed adequate for noninvasive real-time impedance measurements on biological tissues.
{"title":"A Multi-Frequency Focused Impedance Measurement System Based on Analogue Synchronous Peak Detection","authors":"M. A. Kadir, Adrian J. Wilson, K. Siddique-e Rabbani","doi":"10.3389/felec.2021.791016","DOIUrl":"https://doi.org/10.3389/felec.2021.791016","url":null,"abstract":"Monitoring of anatomical structures and physiological processes by electrical impedance has attracted scientists as it is noninvasive, nonionizing and the instrumentation is relatively simple. Focused Impedance Method (FIM) is attractive in this context, as it has enhanced sensitivity at the central region directly beneath the electrode configuration minimizing contribution from neighboring regions. FIM essentially adds or averages two concentric and orthogonal combinations of conventional Tetrapolar Impedance Measurements (TPIM) and has three versions with 4, 6, and 8 electrodes. This paper describes the design and testing of a multi-frequency FIM (MFFIM) system capable of measuring all three versions of FIM at 8 frequencies in the range 10 kHz—1 MHz. A microcontroller based multi-frequency signal generator and a balanced Howland current source with high output impedance (476 kΩ at 10 kHz and 58.3 kΩ at 1 MHz) were implemented for driving currents into biological tissues with an error <1%. The measurements were carried out at each frequency sequentially. The peak values of the amplified voltage signals were measured using a novel analogue synchronous peak detection technique from which the transfer impedances were obtained. The developed system was tested using TPIM measurements on a passive RC Cole network placed between two RC networks, the latter representing skin-electrode contact impedances. Overall accuracy of the measurement was very good (error <4% at all frequencies except 1 MHz, with error 6%) and the resolution was 0.1 Ω. The designed MFFIM system had a sampling rate of >45 frames per second which was deemed adequate for noninvasive real-time impedance measurements on biological tissues.","PeriodicalId":73081,"journal":{"name":"Frontiers in electronics","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-12-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44799250","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-12-09DOI: 10.3389/felec.2021.797308
Oliver Lahr, Max Steudel, H. von Wenckstern, M. Grundmann
Due to their low-temperature processing capability and ionic bonding configuration, amorphous oxide semiconductors (AOS) are well suited for applications within future mechanically flexible electronics. Over the past couple of years, amorphous zinc tin oxide (ZTO) has been proposed as indium and gallium-free and thus more sustainable alternative to the widely deployed indium gallium zinc oxide (IGZO). The present study specifically focuses on the strain-dependence of elastic and electrical properties of amorphous zinc tin oxide thin-films sputtered at room temperature. Corresponding MESFETs have been compared regarding their operation stability under mechanical bending for radii ranging from 5 to 2 mm. Force-spectroscopic measurements yield a plastic deformation of ZTO as soon as the bending-induced strain exceeds 0.83 %. However, the electrical properties of ZTO determined by Hall effect measurements at room temperature are demonstrated to be unaffected by residual compressive and tensile strain up to 1.24 %. Even for the maximum investigated tensile strain of 1.26 %, the MESFETs exhibit a reasonably consistent performance in terms of current on/off ratios between six and seven orders of magnitude, a subthreshold swing around 350 mV/dec and a field-effect mobility as high as 7.5 cm2V−1s−1. Upon gradually subjecting the transistors to higher tensile strain, the channel conductivity steadily improves and consequently, the field-effect mobility increases by nearly 80 % while bending the devices around a radius of 2 mm. Further, a reversible threshold voltage shift of about −150 mV with increasing strain is observable. Overall, amorphous ZTO provides reasonably stable electrical properties and device performance for bending-induced tensile strain up to at least 1.26 % and thus represent a promising material of choice considering novel bendable and transparent electronics.
{"title":"Mechanical Stress Stability of Flexible Amorphous Zinc Tin Oxide Thin-Film Transistors","authors":"Oliver Lahr, Max Steudel, H. von Wenckstern, M. Grundmann","doi":"10.3389/felec.2021.797308","DOIUrl":"https://doi.org/10.3389/felec.2021.797308","url":null,"abstract":"Due to their low-temperature processing capability and ionic bonding configuration, amorphous oxide semiconductors (AOS) are well suited for applications within future mechanically flexible electronics. Over the past couple of years, amorphous zinc tin oxide (ZTO) has been proposed as indium and gallium-free and thus more sustainable alternative to the widely deployed indium gallium zinc oxide (IGZO). The present study specifically focuses on the strain-dependence of elastic and electrical properties of amorphous zinc tin oxide thin-films sputtered at room temperature. Corresponding MESFETs have been compared regarding their operation stability under mechanical bending for radii ranging from 5 to 2 mm. Force-spectroscopic measurements yield a plastic deformation of ZTO as soon as the bending-induced strain exceeds 0.83 %. However, the electrical properties of ZTO determined by Hall effect measurements at room temperature are demonstrated to be unaffected by residual compressive and tensile strain up to 1.24 %. Even for the maximum investigated tensile strain of 1.26 %, the MESFETs exhibit a reasonably consistent performance in terms of current on/off ratios between six and seven orders of magnitude, a subthreshold swing around 350 mV/dec and a field-effect mobility as high as 7.5 cm2V−1s−1. Upon gradually subjecting the transistors to higher tensile strain, the channel conductivity steadily improves and consequently, the field-effect mobility increases by nearly 80 % while bending the devices around a radius of 2 mm. Further, a reversible threshold voltage shift of about −150 mV with increasing strain is observable. Overall, amorphous ZTO provides reasonably stable electrical properties and device performance for bending-induced tensile strain up to at least 1.26 % and thus represent a promising material of choice considering novel bendable and transparent electronics.","PeriodicalId":73081,"journal":{"name":"Frontiers in electronics","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49197645","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-12-06DOI: 10.3389/felec.2021.793780
Zhuo Gao, Shiwei Wang, Yongfu Li, Mingyi Chen
Along with the industrialization and popularization of the wearable electronics, an increasing number of the wireless sensor nodes (WSNs) are deployed. Nevertheless, the conventional battery-based power supply system has no longer satisfied the requirement of large-scale WSNs in terms of battery life, which emerges the energy harvesting (EH) technique. In order to combine various of energy sources and drive multi-loads, the multi-input single-inductor multi-output (MISIMO) EH interface applied to wearable electronics is spotlighted. In this mini-review article, the solutions for improving power conversion efficiency (PCE) and output quality in MISIMO EH interface are summarized. Furthermore, the future trends of MISIMO EH interface are also presented.
{"title":"Review of the Multi-Input Single-Inductor Multi-Output Energy Harvesting Interface Applied in Wearable Electronics","authors":"Zhuo Gao, Shiwei Wang, Yongfu Li, Mingyi Chen","doi":"10.3389/felec.2021.793780","DOIUrl":"https://doi.org/10.3389/felec.2021.793780","url":null,"abstract":"Along with the industrialization and popularization of the wearable electronics, an increasing number of the wireless sensor nodes (WSNs) are deployed. Nevertheless, the conventional battery-based power supply system has no longer satisfied the requirement of large-scale WSNs in terms of battery life, which emerges the energy harvesting (EH) technique. In order to combine various of energy sources and drive multi-loads, the multi-input single-inductor multi-output (MISIMO) EH interface applied to wearable electronics is spotlighted. In this mini-review article, the solutions for improving power conversion efficiency (PCE) and output quality in MISIMO EH interface are summarized. Furthermore, the future trends of MISIMO EH interface are also presented.","PeriodicalId":73081,"journal":{"name":"Frontiers in electronics","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-12-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45377957","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-11-16DOI: 10.3389/felec.2021.777434
Saleem Khan, Shawkat Ali, Arshad Khan, Bo Wang, T. Al-Ansari, A. Bermak
This paper presents a comparative study on the treatment techniques for flexible polymeric substrates and their impact on the printing results. Substrate treatments are central to optimization of the printing processes and a strict set of requirements are needed to achieve uniform and acceptable printing results. Therefore, this research is highlighting the most significant treatment methods used for fine-tuning the surface properties of different polymeric substrates. Besides the two commonly used treatment techniques of oxygen plasma and ultraviolet ozone, a new method of using surface cleaning liquid is applied for rapid treatment of polymeric substrates. Comparative study is carried out on the basis of cleaning steps required for substrate preparation, processing, robustness as well as on the final printed results on the substrates. All the three treatment techniques with similar processing protocol are applied on a single type of polyimide (PI) substrate. To further validate the applicability and manufacture of practical devices, the liquid cleaning method is also applied on Polyethylene terephthalate substrates for making proof-of-concept wearable temperature sensor. From the study it is concluded that the liquid surface cleaning method is advantageous in terms of easy processing, robustness and producing uniform printing results on diverse polymeric substrates.
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