{"title":"Wearable RFID Sensor for Simultaneous Heartbeat and Respiration Monitoring","authors":"Runhao Zhang;Bo Zhang;Zhaozong Meng;Chenxi Li;Haichao Liu;Nan Gao","doi":"10.1109/LSENS.2025.3548147","DOIUrl":"https://doi.org/10.1109/LSENS.2025.3548147","url":null,"abstract":"Novel sensing and communication techniques have created new opportunities for unobtrusive vital sign monitoring. Due to the features of wireless power and data transfer and non-line-of-sight interrogation of radio frequency identification (RFID), its innovative integration with different sensing elements has become a promising solution. Since the heartbeat and respiration signals are weak and their measurement is time-consuming, a lightweight and flexible solution for their unobtrusive wearable sensing remains a challenge. This investigation presents a novel capacitive pressure sensor (CPS)-augmented RFID solution for simultaneous and wearable sensing of heartbeat and respiration. The main contributions include: first, proposal of an innovative RFID-based vital sign monitoring scheme, which integrates a CPS for heartbeat sensing and employs RFID phase signals for respiration sensing; second, design and fabrication of a polydimethylsiloxane (PDMS)-based flexible and porous slotted CPS for continuous heartbeat sensing; and third, development of respiration signal reconstruction algorithm using the weak and noisy RFID phase integrating phase disambiguation, denoising, baseline removal, and peak detection. Experimental studies are conducted to verify the feasibility and effectiveness of the presented techniques.","PeriodicalId":13014,"journal":{"name":"IEEE Sensors Letters","volume":"9 4","pages":"1-4"},"PeriodicalIF":2.2,"publicationDate":"2025-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143667611","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}
{"title":"Electroactive Flexible Sensor for Selective L-Ascorbic Acid Detection Using Polyaniline-Decorated Phosphotungstic Acid/Copper Composite","authors":"Sajina Selvaraj;Archana S;Ragupathy D;Vinoth Kumar Ponnusamy;Muthusankar Eswaran","doi":"10.1109/LSENS.2025.3571539","DOIUrl":"https://doi.org/10.1109/LSENS.2025.3571539","url":null,"abstract":"In this letter, we spotlight a flexible stainless steel (FSS)-based hybrid electrode with phosphotungstic acid-copper-embedded poly (aniline) (FSS/PANI/PTA/Cu) composite for the efficient detection of L-ascorbic acid (AA). Single pot electrodeposition has been engaged in fabricating PANI/PTA/Cu composite on FSS via cyclic voltammetry (CV). The successful composite fabrication has been authenticated through physicochemical characterization, including its structural geometry, surface morphology, and molecular vibrational properties, which were analyzed through X-ray crystallography, field emission scanning electron microscopy, infrared spectroscopy and UV-Vis spectrophotometers. The electrochemical sensing performances were examined using CV and chronoamperometric analysis. The flexible sensor measured a sensitivity of 3.79 mA/mM with a detection limit of 7.9 µM for AA. This performance results from the combined synergetic action of PANI, PTA, and Cu, which enabled efficient ionic diffusion and seamless electron transfer through a high density of accessible electroactive sites. In addition, the flexible sensor electrode exhibited remarkable selectivity for AA, with negligible interference from coexisting species, highlighting its potential for healthcare diagnostic applications in near future.","PeriodicalId":13014,"journal":{"name":"IEEE Sensors Letters","volume":"9 7","pages":"1-4"},"PeriodicalIF":2.2,"publicationDate":"2025-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144255740","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}
{"title":"Performance Evaluation for a Muddy Water Contamination on Autonomous Sensors","authors":"Sungho Shin;Namkyun Kim;Wancheol Gim;Hun-Jae Kim;Joon Woo Lee;Hyuntaeck Lim","doi":"10.1109/LSENS.2025.3553101","DOIUrl":"https://doi.org/10.1109/LSENS.2025.3553101","url":null,"abstract":"Autonomous driving systems depend heavily on advanced recognition sensors, such as light detection and ranging, radar, cameras, and ultrasonic sensors, to navigate dynamic environments safely and effectively. However, these sensors are vulnerable to environmental contamination, particularly from muddy water, which can significantly degrade their optical performance. This letter presents a standardized method for evaluating the impact of muddy water contamination on recognition sensor cover with a focus on assessing transmittance reduction. An automated injection system was employed to apply varying levels of contamination to polycarbonate windows, and transmittance was estimated based on a pulsed laser module. The proposed method demonstrated that practical applicability was achieved by comparison with real-world contamination during test driving and laboratory findings. This research will provide a reliable, standardized approach to quantify the effects of various contaminations on sensor performance, also contributing to the development of more robust autonomous driving technologies capable of operating in harsh environmental conditions.","PeriodicalId":13014,"journal":{"name":"IEEE Sensors Letters","volume":"9 4","pages":"1-4"},"PeriodicalIF":2.2,"publicationDate":"2025-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143769410","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}
{"title":"Fluidic-Integrated Dielectric Waveguide Mach–Zehnder Sensor for THz Spectroscopy","authors":"Kristof Dausien;Dennis Pohle;Nils Pohl;Ilona Rolfes;Jan Barowski;Christian Schulz","doi":"10.1109/LSENS.2025.3571545","DOIUrl":"https://doi.org/10.1109/LSENS.2025.3571545","url":null,"abstract":"This letter presents the design, optimization, and characterization of a dielectric slot-waveguide (DSWG)-based sensor for fluid sensing applications. The sensor is inspired by the concept of a Mach–Zehnder interferometer and utilizes high field confinement within the slot region to enhance sensitivity to permittivity changes, overcoming typical problems of other fluidic terahertz (THz) domain sensors. Advanced 3D-electromagnetic simulations were employed to optimize key design parameters, ensuring low loss and efficient sensing performance. Measurements with acetone, isopropanol, and butanol demonstrate the sensor's ability to distinguish fluids based on their permittivity, with notable differences in time shifts and attenuation. These results highlight the potential of DSWG-based sensors for precise and reliable THz sensing applications.","PeriodicalId":13014,"journal":{"name":"IEEE Sensors Letters","volume":"9 6","pages":"1-4"},"PeriodicalIF":2.2,"publicationDate":"2025-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=11007499","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144213571","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}
Manish Pandey;Shubham Sharma;Shyam S. Pandey;Masakazu Nakamura
{"title":"High Responsivity in Near-Infrared Phototransistor With Oriented Polymer Semiconductors","authors":"Manish Pandey;Shubham Sharma;Shyam S. Pandey;Masakazu Nakamura","doi":"10.1109/LSENS.2025.3549783","DOIUrl":"https://doi.org/10.1109/LSENS.2025.3549783","url":null,"abstract":"Near-infrared organic phototransistors (OPTs) in bottom-gated top-contact structures are being reported using an oriented p-type diketopyrrolopyrrole-based semiconducting polymer (SCP) (DPPT-TT). Here, highly oriented DPPT-TT floating films were prepared on a liquid substrate using the unidirectional floating-film transfer method (UFTM) and then utilized as the active layer. This innovative approach exhibits a dual-orientation advantage: They align polymer chains unidirectionally, enhancing charge transport along the backbone while simultaneously promoting an edge-on molecular arrangement relative to the substrate. This combination, coupled with highly uniform thin films, facilitates efficient charge transport pathways, contributing significantly to the fabrication of high-performance OPTs. Our DPPT-TT-based OPT exhibited a high field-effect mobility of 1.5 cm<sup>2</sup>·V<sup>−1</sup>·s<sup>−1</sup> and photoresponsivity (R) > 10<sup>5</sup> A·W<sup>−1</sup> at an intensity of 45 <italic>μ</i>W·cm<sup>−2</sup> under 810 nm light illumination. This exceptional performance is attributed to faster carrier transport and efficient charge collection in the oriented DPPT-TT films enabled by the UFTM.","PeriodicalId":13014,"journal":{"name":"IEEE Sensors Letters","volume":"9 4","pages":"1-4"},"PeriodicalIF":2.2,"publicationDate":"2025-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143769379","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}
{"title":"Aluminum Doped Zinc Oxide and Silver Nanowire Composite Based Printed CO$_{2}$ Gas Sensor","authors":"Nikhila Patil;Neethu Thomas;Neha Sharma;Parasuraman Swaminathan;P. Sumathi","doi":"10.1109/LSENS.2025.3571193","DOIUrl":"https://doi.org/10.1109/LSENS.2025.3571193","url":null,"abstract":"Carbon dioxide (CO<inline-formula><tex-math>$_{2}$</tex-math></inline-formula>) is a significant greenhouse gas and an essential indicator of effective air circulation in enclosed spaces, requiring precise and continuous monitoring. Traditional chemiresistive CO<inline-formula><tex-math>$_{2}$</tex-math></inline-formula> sensors have high operating temperatures that require external heating elements limiting their applicability in low-power portable electronics. This work demonstrates a miniaturized printed CO<inline-formula><tex-math>$_{2}$</tex-math></inline-formula> gas sensor, based on aluminum-doped zinc oxide (AZO) and silver nanowire (Ag NW) nanocomposite ink, which operates efficiently at room temperature. The AZO-Ag NW nanocomposite ink is optimized for direct ink writing (DIW) to obtain a uniform printed pattern. The composite ink helps overcome the inherent high resistance of AZO nanostructures by taking advantage of Ag NW's high conductivity and surface reactivity. The sensor shows a quick response time of 19 s and a recovery time of 36 s for 400 ppm CO<inline-formula><tex-math>$_{2}$</tex-math></inline-formula>. The sensor exhibits a response (R) of 32.5% with a limit of detection of 24.04 ppm, while operating at a low bias of 1 V. The integration of DIW, cost-effective ink formulation, and scalable fabrication is a significant advancement for real-time CO<inline-formula><tex-math>$_{2}$</tex-math></inline-formula> monitoring at low power.","PeriodicalId":13014,"journal":{"name":"IEEE Sensors Letters","volume":"9 6","pages":"1-4"},"PeriodicalIF":2.2,"publicationDate":"2025-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144179174","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}