Ultra-Tough Waterborne Polyurethane-Based Graft-Copolymerized Piezoresistive Composite Designed for Rehabilitation Training Monitoring Pressure Sensors

Bioinspired Interlocked Nanostructured Piezoresistive Composite for Monitoring of Renal Pelvic Pressure

Inspired by the structure of Setaria viridis and based on guidance of molecular dynamics simulations, a hierarchical nanospike structure on micrometer-sized coaxial fibers has been designed at the molecular scale. A piezoresistive composite membrane of in situ-grown PDA-PPy on a TPU@PES coaxial fiber has been prepared, exhibiting good anticreep performance, high sensitivity, and fast response. The matrix material is designed as coaxial fibers, which consist of an inner PES core that provides anticreep mechanical support and an outer thermoplastic polyurethane shell that offers a large specific surface area and rich graft reaction sites. The nanospike semiconductor phase constructs an interlocking structured composite by forming a multihierarchical conducting network. The piezoresistive sensor constructed with this composite exhibits ultrahigh sensitivity (27.1 kPa-1) and quick response (23.1 ms response time and 26.3 ms recovery time). Furthermore, the chemical grafting process ensures a stable interface between the semiconductor phase and matrix material by creating covalent and hydrogen bonds. This interface not only prevents instability but also demonstrates excellent signal recovery performance and dynamic stability (10,000 cycles). Monitoring changes in renal pelvic pressure with a 3D-printed artificial renal pelvis was performed, confirming its practicality for medical monitoring.

Multifunctional, UV Radiation Shielding and High Bacteriostatic Efficiency 3D Wearable Sensor Triggered by ZIF-67

3D multifunctional wearable piezoresistive sensors have aroused extensive attention in the fields of motion detection, human-computer interaction, electronic skin, etc. However, current research mainly focuses on improving the foundational performance of piezoresistive sensors, while many advanced demands are often ignored. Herein, a 3D piezoresistive sensor based on rGO@C-ZIF-67@PU is fabricated via high temperature carbonization and a solvothermal reduction method. The as-prepared sensor exhibits a high sensitivity of 245.4 kPa-1, a wide detection range (0-25 kPa), a fast response/recovery time (30 ms/50 ms), and excellent durability (over 5000 cycles). Apart from the outstanding sensing performance, this sensor also displays UV shielding properties and excellent antibacterial activity, providing a broader application prospect for this hybrid sensor. Besides, the optic nerve damage/loss can be compensated to some extent via combining this multifunctional 3D piezoresistive sensor with traditional guide sticks, thus assisting visually impaired people to integrate into social life and normal social interaction easily. Evidently, these outstanding features pave a promising avenue to overcome the limitation of the existing piezoresistive sensors and provide a general way to promote its broad commercial applications.

Smart Driving Hardware Augmentation by Flexible Piezoresistive Sensor Matrices with Grafted-on Anticreep Composites

Signal drift and hysteresis of flexible piezoresistive sensors pose significant challenges against the widespread applications in emerging fields such as electronic skin, wearable equipment for metaverse and human-AI (artificial intelligence) interfaces. To address the creep and relaxation issues associated with pressure-sensitive materials, a highly stable piezoresistive composite is proposed, using polyamide-imide (PAI) fibers as the matrix and in situ grafted-polymerized polyaniline (PANI) as the semi-conducting layer. The PAI with large rigid fluorenylidene groups exhibits a high glass transition temperature of 372 °C (PAI 5-5), which results in an extremely long relaxation time at room temperature and consequently offers outstanding anti-creep/relaxation performances. The enhancement of PAI-PANI interfacial bonding through in situ grafting improves the sensor reliably. The sensor presents high linear sensitivity of 35.3 kPa-1 over a pressure range of 0.2-20 kPa, outstanding repeatability, and excellent dynamic stability with only a 3.8% signal deviation through ≈10 000 cycles. Real-time visualization of pressure distribution is realized by sensor matrices, which demonstrate the capability of tactile gesture recognition on both flat and curved surfaces. The recognition of sitting postures is achieved by two 12 × 12 matrices facilitated by machine learning, which prompts the potential for the augmentation of smart driving.

Creep-free polyelectrolyte elastomer for drift-free iontronic sensing

Artificial pressure sensors often use soft materials to achieve skin-like softness, but the viscoelastic creep of soft materials and the ion leakage, specifically for ionic conductors, cause signal drift and inaccurate measurement. Here we report drift-free iontronic sensing by designing and copolymerizing a leakage-free and creep-free polyelectrolyte elastomer containing two types of segments: charged segments having fixed cations to prevent ion leakage and neutral slippery segments with a high crosslink density for low creep. We show that an iontronic sensor using the polyelectrolyte elastomer barely drifts under an ultrahigh static pressure of 500 kPa (close to its Young's modulus), exhibits a drift rate two to three orders of magnitude lower than that of the sensors adopting conventional ionic conductors and enables steady and accurate control for robotic manipulation. Such drift-free iontronic sensing represents a step towards highly accurate sensing in robotics and beyond.