With the advent of the Internet of Things (IoT) era, flexible sensors are regarded as one of the most important technologies for the development of humanfriendly wearable devices. Organic field-effect transistors (OFETs) based on conjugated polymers or small molecules are promising sensor platforms because they have various advantages, including high sensitivity, mechanical flexibility, and low-cost fabrication processes. OFET-based sensors enable continuous monitoring of external stimuli or target analytes with superior detection capabilities. This review describes the working principles and sensing mechanisms of various OFET-based sensors, including chemical, biological, photo, pressure, and temperature sensors, and introduces the recent progress in this field. In addition, the technical challenges and future outlook of OFETbased sensors for next-generation flexible electronics are briefly discussed.

Polymer-based pressure sensors play a key role in realizing lightweight and inexpensive wearable devices for healthcare and environmental monitoring systems. Here, conductive core/shell polymer nanofibers composed of poly (vinylidene fluoride-co-hexafluoropropene) (PVDF-HFP)/poly(3,4-ethylenedioxythiophene) (PEDOT) are fabricated using three-dimensional (3D) electrospinning and vapor deposition polymerization methods, and the resulting sponge-like 3D membranes are used to create piezoresistive-type pressure sensors. Interestingly, the PEDOT shell consists of well-dispersed spherical bumps, leading to the formation of a hierarchical conductive surface that enhances the sensitivity to external pressure. The sponge-like 3D mats exhibit a much higher pressure sensitivity than the conventional electrospun 2D mats due to their enhanced porosity and pressure-tunable contact area. Furthermore, large-area, wireless, 16 × 10 multiarray pressure sensors for the spatiotemporal mapping of multiple pressure points and wearable bands for monitoring blood pressure have been fabricated from these 3D mats. To the best of our knowledge, this is the first report of the fabrication of electrospun 3D membranes with nanoscopically engineered fibers that can detect changes in external pressure with high sensitivity. The developed method opens a new route to the mass production of polymer-based pressure sensors with high mechanical durability, which creates additional possibilities for the development of human-machine interfaces.

Novel ZnO/TiO(2) composite nanofibers were fabricated by an electrospinning method and showed excellent antimicrobial activity against gram-negative Escherichia coli and gram-positive Staphylococcus aureus under UV irradiation and in the absence of light.

This review describes the development status of organic sensors for health-monitoring systems and the strategies to enhance their performance.

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Multifunctional hydrogels with properties including transparency, flexibility, self-healing, and high electrical conductivity have attracted great attention for their potential application to soft electronic devices. The presence of an ionic species can make hydrogels conductive in nature. However, the conductivity of hydrogels is often influenced by temperature, due to the change of the internal nano/microscopic structure when temperature reaches the sol−gel phase transition temperature. In this regard, by introducing a novel surface-capacitive sensor device based on polymers with lower critical solution temperature (LCST) behavior, near-perfect stimulus discriminability of touch and temperature may be realized. Here, we demonstrate a multimodal sensor that can monitor the location of touch points and temperature simultaneously, using poly(N-isopropylacrylamide) (PNIPAAm) in hybrid poly(vinyl alcohol) (PVA) and sodium tetraborate decahydrate cross-linked hydrogels doped with poly(sodium acrylate) (SA) [w/w/w = 5:2.7:1−3]. This multimodal sensor exhibits a response time of 0.3 s and a temperature coefficient of resistance of −0.58% K −1 from 20 to 40 °C. In addition, the LCST behavior of PNIPAAmincorporated PVA/SA gels is investigated. Incorporation of LCST polymers into high-end hydrogel systems may contribute to the development of temperature-dependent soft electronics that can be applied in smart windows.

Electrospun semiconducting polymer nanofibers functionalized with specific container molecules have been used for flexible and high-performance chemical sensors.

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