Dual-Stage Surficial Microstructure to Enhance the Sensitivity of MXene Pressure Sensors for Human Physiological Signal Acquisition

ZnO Nanostructure-Based Flexible Pressure Sensors Deposited on Filter Paper for Wearable Application

Flexible pressure sensors have broad prospects in smart wearables, healthcare, and human-computer interaction. Nevertheless, flexible pressure sensors still face numerous thorny challenges. It has become a crucial problem to skillfully design and successfully achieve flexible pressure sensors with both a high sensing range and ultrahigh sensitivity. The sensor is designed and realized with inspiration drawn from the layered microstructure of human skin, and hierarchical structure flexible pressure sensors are fabricated, where PDMS microstructures/MWCNTs act as the top electrode, filter paper/ZnO nanostructures/MWCNTs act as the intermediate active layer, and an Ag interdigitated electrode acts as the bottom electrode. The sensing performance of the sensor is investigated to develop the application of pressure sensors for human health detection in daily life, and a pressure sensor array is prepared to investigate the detection of spatial pressure distribution. Sensors based on paper and PDMS can achieve low-pressure detection (30 Pa), high sensitivity (261.38 kPa-1), fast response time (∼73.8 ms), and excellent cyclic stability (10 000 cycles). Finally, the sensor demonstrates its functionality by lighting up a small lamp, which confirms that the as-prepared pressure sensor has excellent application scenarios and is beneficial for the development of flexible electronic devices.

A Bionic Textile Sensory System for Humanoid Robots Capable of Intelligent Texture Recognition

Artificial tactile perception systems that emulate the functions of slow adaptive (SA) and fast adaptive (FA) cutaneous mechanoreceptors are essential for developing advanced prosthetics and humanoid robots. However, constructing a high-performance sensory system within a single device capable of simultaneously perceiving both static and dynamic forces for surface-texture recognition remains a critical challenge; this contrasts with common strategies integrating individual SA- and FA-mimicking sensors in multi-layered, multi-circuit configurations. Herein, a textile pressure/tactile (PT) sensor is reported based solely on piezoresistive principle alongside high sensitivity and rapid response to both high-frequency vibrations and static forces. These characteristics are attributed to the sensor's 3D multiscale architecture and the corresponding hierarchical structural deformation of its honeycomb-like sensing fabric. As a proof-of-concept application relevant to humanoid robotics and prosthetics, an automated surface-texture-recognition system is constructed by integrating the PT sensor with machine-learning algorithms, a prosthetic device, an industrial robot arm, and a graphical user interface. This artificial sensory system demonstrates the ability to learn distinct object features, differentiate fine surface textures, and subsequently classify unknown textiles with high recognition accuracy (>98.9%) across a wide range of scanning speeds (50-300 mm s-1). These results show promise for the future development of interactive artificial intelligence.

Flexible Piezoresistive Film Pressure Sensor Based on Double-Sided Microstructure Sensing Layer

Flexible thin-film pressure sensors have garnered significant attention due to their applications in industrial inspection and human-computer interactions. However, due to their ultra-thin structure, these sensors often exhibit lower performance, including a narrow pressure response range and low sensitivity, which constrains their further application. The most commonly used microstructure fabrication methods are challenging to apply to ultra-thin functional layers and may compromise the structural stability of the sensors. In this study, we present a novel design of a film pressure sensor with a double-sided microstructure sensing layer by adopting the template method. By incorporating the double-sided microstructures, the proposed thin-film pressure sensor can simultaneously achieve a high sensitivity value of 5.5 kPa-1 and a wide range of 140 kPa, while maintaining a short response time of 120 ms and a low detection limit. This flexible film pressure sensor demonstrates considerable potential for distributed pressure sensing and industrial pressure monitoring applications.

Intelligent Song Recognition via a Hollow-Microstructure-Based, Ultrasensitive Artificial Eardrum

Artificial ears with intelligence, which can sensitively detect sound-a variant of pressure-and generate consciousness and logical decision-making abilities, hold great promise to transform life. However, despite the emerging flexible sensors for sound detection, most success is limited to very simple phonemes, such as a couple of letters or words, probably due to the lack of device sensitivity and capability. Herein, the construction of ultrasensitive artificial eardrums enabling intelligent song recognition is reported. This strategy employs novel geometric engineering of sensing units in the soft microstructure array (to significantly reduce effective modulus) along with complex song recognition exploration leveraging machine learning algorithms. Unprecedented pressure sensitivity (6.9 × 103 kPa-1) is demonstrated in a sensor with a hollow pyramid architecture with porous slants. The integrated device exhibits unparalleled (exceeding by 1-2 orders of magnitude compared with reported benchmark samples) sound detection sensitivity, and can accurately identify 100% (for training set) and 97.7% (for test set) of a database of the segments from 77 songs varying in language, style, and singer. Overall, the results highlight the outstanding performance of the hollow-microstructure-based sensor, indicating its potential applications in human-machine interaction and wearable acoustical technologies.

High-Performance Flexible Pressure Sensor with Micropyramid Structure for Human Motion Signal Detection and Electromagnetic Interference Shielding

Flexible pressure sensors have a wide range of applications in the field of human motion signal detection, but the electromagnetic radiation generated during the monitoring process has become an unavoidable problem. Nowadays, it is still a challenge to develop high-performance pressure sensors with excellent electromagnetic interference (EMI) shielding performance. Herein, the Ti3C2TX MXene/carbon fiber/multiwalled carbon nanotube/polydimethylsiloxane (MXene/CMP) films with a micropyramidal structure were developed by the technology of vacuum high-temperature hot pressing and spray deposition. Benefiting from the dielectric loss of the conductive fillers and the presence of the microstructure, the MXene/CMP film exhibits excellent EMI shielding performance, and the EMI shielding efficiency (SE) can reach 49.37 dB. Besides, the introduction of CF effectively improves the mechanical properties of the MXene/CMP films, and the MXene nanosheets deposited on the surface of the film can reduce stress concentration, which in turn delays the expansion of cracks. Furthermore, the MXene/CMP sensor exhibits high sensitivity (89.76 kPa-1) and fast response/recovery time (61/60 ms). The deformation of microstructure and the construction of conductive networks enable the sensor to realize the monitoring of human motion signals (such as finger bending, knee bending, wrist bending, etc.). Meanwhile, the sensor maintains sensing stability even after 2000 pressure cycles, which can be attributed to the improvement in mechanical properties. In summary, the developed high-performance flexible pressure sensor with micropyramid structure has great application prospects in wearable devices and healthcare.

A Novel Hollow Graphene/Polydimethylsiloxane Composite for Pressure Sensors with High Sensitivity and Superhydrophobicity

Flexible pressure sensors have attracted great interest as they play an important role in various fields such as health monitoring and human-machine interactions. The design of the pressure sensors still faces challenges in achieving a high sensitivity for a wide sensing range, and the interference of water restricts the applications of the sensors. Herein, we developed a graphene-polydimethylsiloxane film combining a hierarchical surface with nanowrinkles on it and a hollow structure. The microstructure design of the composite can be facilely controlled to improve the sensing and hydrophobic performance by tailoring the microsphere building units. Attributed to the irregular surface and hollow structure of the sensing layer, the optimized sensor exhibits a superior sensitivity of 1085 kPa-1 in a 50 kPa linear range. For practical applications, the nanowrinkles on the surface of the microspheres and the polymer coating endow the composite with waterproof properties. Inspired by the dual receptors of the skin, two designed microstructured films can simply integrate into one with double-sided microstructures. The sensing performance and the water-repellence property allow the sensor to detect physiological signals under both ambient and underwater conditions. Furthermore, underwater stimuli detection and communication are demonstrated. This method of fabricating a flexible sensor shows great potential in wearable and robotic fields.

Recent Advances in Wearable Healthcare Devices: From Material to Application

In recent years, the proliferation of wearable healthcare devices has marked a revolutionary shift in the personal health monitoring and management paradigm. These devices, ranging from fitness trackers to advanced biosensors, have not only made healthcare more accessible, but have also transformed the way individuals engage with their health data. By continuously monitoring health signs, from physical-based to biochemical-based such as heart rate and blood glucose levels, wearable technology offers insights into human health, enabling a proactive rather than a reactive approach to healthcare. This shift towards personalized health monitoring empowers individuals with the knowledge and tools to make informed decisions about their lifestyle and medical care, potentially leading to the earlier detection of health issues and more tailored treatment plans. This review presents the fabrication methods of flexible wearable healthcare devices and their applications in medical care. The potential challenges and future prospectives are also discussed.