Wearable high-performance pressure sensors based on three-dimensional electrospun conductive nanofibers

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. A flexible material for creating wearable pressure sensors has been manufactured by scientists in Korea using a simple and cost-effective nanofiber-spinning technique. Wearable electronics require pliable materials that also conduct electricity. Joon Hak Oh and co-workers from Pohang University of Science and Technology (POSTECH), South Korea, developed a pressure-sensitive material using electrospinning and vapor deposition polymerization. Conventionally, electrospinning forces a polymer solution through a narrow nozzle to create a two-dimensional network of fibers. These layers are then stacked to create a three-dimensional structure, but the small gaps between layers makes it less sensitive to forces applied from the top. The researchers manufactured a sponge-like three-dimensional nanofiber mat, which they coated with a spherical bump-shape conducting polymer. This three-dimensional membrane was nearly three times more sensitive to pressure changes than structures prepared using two-dimensional electrospinning. PVDF-HFP/PEDOT core/shell nanofibers with well-dispersed spherical bumps have been prepared using 3D electrospinning and vapor deposition polymerization methods, and their sponge-like 3D membranes are used to create piezoresistive-type pressure sensors. Owing to the enhanced porosity and pressure-tunable contact area, the sensors exhibit outstanding mechanoelectrical performance. Furthermore, large-area, wireless, 16 × 10 multi-array pressure sensors for spatiotemporal mapping of multiple pressing points and wearable bands for monitoring blood pressure have been fabricated from these 3D mats. The developed method opens up a new route for the mass production of polymer-based sensors, which is promising for biomedical diagnostics and environmental monitoring systems.