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The ever-increasing number of devices on wearable and portable systems comes with challenges such as integration complexity, higher power requirements, and less user comfort. In this regard, the development of multifunctional devices could help immensely as they will provide the same functionalities with lesser number of devices. Herein, we present a dual-function flexible loop antenna printed on polyvinyl chloride (PVC) substrate. With a poly(3,4-ethylenedioxythiophene): polystyrene (PEDOT:PSS) section as part of the printed structure, the presented antenna can also serve as a temperature sensor by means of change in resistance. The antenna resonates at 1.2- and 5.8-GHz frequencies. The ohmic resistance of the temperature sensing part decreases by ~70% when the temperature increases from 25 °C to 90 °C. The developed antenna was characterized using a vector network analyzer (VNA) in the same temperature range and the S11 magnitude was found to change by ~3.5 dB. The induced current was also measured in the GSM frequency range and sensitivity of ~1.2%/°C was observed for the sensing antenna. The flexible antenna was also evaluated in lateral and cross-bending conditions and the response was found to be stable for the cross-bending. Due to these unique features, the presented antenna sensor could play a vital role in the drive toward ubiquitous sensing through wearables, smart labels, and the Internet of Things (IoT).

This article presents a smart bandage with wireless strain and temperature sensors and a batteryless near-field communication (NFC) tag. Both sensors are based on conductive poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) polymer. The highly sensitive strain sensor consists of a microfluidic channel filled with PEDOT:PSS in Polydimethylsiloxane (PDMS) substrate. The strain sensor shows 3 order (~1250) increase in the resistance for 10% strain and considerably high gauge factor (GF) of ~12 500. The sensor was tested for ~30% strain, which is more than typical stretching of human skin or body parts such as chest expansion during respiration. The strain sensor was also tested for different bending and the electrical resolution was ~150% per degree of free bending and ~12k% per percentage of stretching. The resistive temperature sensor, fabricated on a Polyvinyl Chloride (PVC) substrate, showed a ~60% decrease in resistance when the temperature changed from 25 °C to 85 °C and a sensitivity of ~1% per °C. As a proof of concept, the sensors and NFC tag were integrated on wound dressing to obtain wearable systems with smart bandage form factor. The sensors can be operated and read from distance of 25 mm with a user-friendly smartphone application developed for powering the system as well as real-time acquisition of sensors data. Finally, we demonstrate the potential use of smart bandage in healthcare applications such as assessment of wound status or respiratory diseases, such as asthma and COVID-19, where monitoring via wearable strain (e.g., respiratory volume) and temperature sensors is critical.

Pancreatic disorders, originating from alcoholism or other sources, have grown into an epidemic in modern society. It is now well known that regular monitoring of -amylase and lipase activities in the blood serum is crucial to judge the condition of the pancreas and assess progress in treatment. However, there is hardly any gadget available at the user's site which can provide guidance on pancreatic health. The present spectroscopic techniques used in pathological laboratories are not only costly but also involve significant time and expertise for testing and analysis. In view of the above, we report the development of a paper-based chemiresistive sensor for the quantitative detection of lipase concentration in human serum. The sensor can be integrated with a point-of-care-testing (POCT) device to provide affordable primary healthcare related to the pancreatic disorders. The hydrolysis of olive oil with lipase present in human blood serum results in the generation of H ions on a reduced graphene oxide-coated paper substrate. A linear variation in electrical resistance with lipase loading in serum configured the working principle of the sensor. The sensors are characterized and calibrated with known concentrations of lipase followed by successful validation with real-life human serum samples. The lower cost, simpler operation, smaller response time, and easy disposability of the sensors ensure their suitability to evolve into a POCT kit for the regular monitoring of pancreatic health at the user's end.