Post-surgical treatments of the human throat often require continuous monitoring of diverse vital and muscle activities. However, wireless, continuous monitoring and analysis of these activities directly from the throat skin have not been developed. Here, we report the design and validation of a fully integrated standalone stretchable device platform that provides wireless measurements and machine learning-based analysis of diverse vibrations and muscle electrical activities from the throat. We demonstrate that the modified composite hydrogel with low contact impedance and reduced adhesion provides high-quality long-term monitoring of local muscle electrical signals. We show that the integrated triaxial broad-band accelerometer also measures large body movements and subtle physiological activities/vibrations. We find that the combined data processed by a 2D-like sequential feature extractor with fully connected neurons facilitates the classification of various motion/speech features at a high accuracy of over 90%, which adapts to the data with noise from motion artifacts or the data from new human subjects. The resulting standalone stretchable device with wireless monitoring and machine learning-based processing capabilities paves the way to design and apply wearable skin-interfaced systems for the remote monitoring and treatment evaluation of various diseases.

The laser-engraved method was introduced to fabricate the electrode for the sensor. The sensor showed a wide linear working range, superior sensitivity, and fast response time and also exhibited excellent viability in a wet situation. Wireless integrated network sensors successfully monitored the health states. Developing flexible sensors with high working performance holds intense interest for diverse applications in leveraging the Internet-of-things (IoT) infrastructures. For flexible piezoresistive sensors, traditionally most efforts are focused on tailoring the sensing materials to enhance the contact resistance variation for improving the sensitivity and working range, and it, however, remains challenging to simultaneously achieve flexible sensor with a linear working range over a high-pressure region (> 100 kPa) and keep a reliable sensitivity. Herein, we devised a laser-engraved silver-coated fabric as “soft” sensor electrode material to markedly advance the flexible sensor’s linear working range to a level of 800 kPa with a high sensitivity of 6.4 kPa⁻¹ yet a fast response time of only 4 ms as well as long-time durability, which was rarely reported before. The integrated sensor successfully routed the wireless signal of pulse rate to the portable smartphone, further demonstrating its potential as a reliable electronic. Along with the rationally building the electrode instead of merely focusing on sensing materials capable of significantly improving the sensor’s performance, we expect that this design concept and sensor system could potentially pave the way for developing more advanced wearable electronics in the future. The online version of this article (10.1007/s40820-020-00498-y) contains supplementary material, which is available to authorized users.

Monitoring biophysical signals such as body or organ movements and other physical phenomena is necessary for patient rehabilitation. However, stretchable flexible pressure sensors with high sensitivity and a broad range that can meet these requirements are still lacking. Herein, we successfully monitored various vital biophysical features and implemented in-sensor dynamic deep learning for knee rehabilitation using an ultrabroad linear range and high-sensitivity stretchable iontronic pressure sensor (SIPS). We optimized the topological structure and material composition of the electrode to build a fully stretching on-skin sensor. The high sensitivity (12.43 kPa⁻¹), ultrabroad linear sensing range (1 MPa), high pressure resolution (6.4 Pa), long-term durability (no decay after 12000 cycles), and excellent stretchability (up to 20%) allow the sensor to maintain operating stability, even in emergency cases with a high sudden impact force (near 1 MPa) applied to the sensor. As a practical demonstration, the SIPS can positively track biophysical signals such as pulse waves, muscle movements, and plantar pressure. Importantly, with the help of a neuro-inspired fully convolutional network algorithm, the SIPS can accurately predict knee joint postures for better rehabilitation after orthopedic surgery. Our SIPS has potential as a promising candidate for wearable electronics and artificial intelligent medical engineering owing to its unique high signal-to-noise ratio and ultrabroad linear range.

Flexible sensors with proximity and tactile sensing have attracted great interest in electronic skins (E-skin), human-machine interfaces (HMI), and soft robotics. However, it remains challenging to have both proximity and haptic sensing ability in one flexible device, yet enable wireless sensing. Here, based on the edge electric field and piezo-capacitive effect, we successfully present a combination of approaching non-contact sensation with pressure perception in one flexible dual-mode capacitive sensor (FDCS) which possesses both proximity-tactile interface interaction and wireless sensing. Large scale and low-cost methods of the screen printing and the laser engraving are selectively used to fabricate flexible electrodes and cone-pattern mold, respectively. Thanks to the stable conductivity of the electrodes and the micro-cone-like dielectric structure, the FDCS exhibits a detection distance of up to 20 cm in proximity mode and an extended operating range of 200 kPa, a low detection limit (10.2 Pa), fast response time (90 ms), and long endurance (>10,000 cycles) in pressure mode. A 64-unit pressure matrix successfully interacted with the coupling of the proximity finger and the actual pressure in two different modes. In addition, by assembling the FDCS with a planar spiral coil to form an LC (inductance-capacitance) resonator, rather than connecting directly to an LCR device, the device was able to detect external pressure wirelessly. The development of this dual-mode sensor and its demonstration paves the way for potential flexible sensors for applications in HMI and soft robots.

Flexible pressure sensors hold great potential for applications in human–machine interaction and flexible robotics, but the balance of their sensitivity and sensing range remains a challenge. Here, we proposed a flexible piezoresistive pressure sensor based on poly (3,4-ethylenedioxythiophene):poly(styrene sulfonic acid) (PEDOT: PSS) and cross interlocked nylon fabrics. The sensor exhibited a wide sensing range (~1.5 mPa), a low detection limit (6 Pa), a fast response time (less than 40 ms), and an excellent cycling stability (at least 16 000 cycles without any decay). The excellent performance is attributed to the fact that the cross interlocked structure can form a mechanically stable and three-dimensional (3D) sensitive conductive network which allowed a contact area of the pressure sensor to vary continuously, resulting in an extremely large pressure sensing range. In addition, the sensor array system was successfully fabricated and integrated with a rank scanning circuit to achieve mapping and identification of spatial pressure distribution. Finally, we have built and demonstrated a sensing system capable of wireless real-time gesture interaction with a robot. These results provide a new direction for the fabrication of high-performance sensors with tremendous applications for healthcare, wearable electronics, electronic skin, and smart robots.

Soft piezocapacitive sensor, owing to its simple assembly and low power consumption, draws intensive interests for physiological monitoring. However, crosstalk between proximity sensing units and limited mechanically stretching suppressed its practical application for conventional capacitive sensor array. Here we report a stretchable iontronic pressure sensor (SIPS) array with low proximate crosstalk for epidermal monitoring. Benefiting from electric double layer (EDL) capacitance effect between robust aramid nanofiber (ANF) /MXene (Ti3C2Tx) composite electrode and ionic film, the SIPS exhibits a high sensitivity up to 521.69 kPa−1, low limit of detection (0.22 Pa), broad linear sensing range (200 kPa) and rapid response time (17 ms) as well as long-term stable working durability for 10,000 cycles. The serpentine island bridge structure enables the SIPS array to stretch up to 40%, allowing pulse and grip monitoring of a bent wrist and finger, respectively, through processing circuits. This demonstrates the promising application prospects in vital physiological monitoring.