ALLPCB
Overview
Pressure-sensing piezoresistive sensors are key components for next-generation health monitoring, human–machine interaction, and robotics. They convert external pressure into electrical signals and are valued for simple sensing mechanisms, convenient signal acquisition, and favorable electromechanical performance. Achieving both high sensitivity and a wide linear sensing range in a single sensor remains a significant challenge.
Researchers at Shanghai Jiao Tong University led by Professor Zhao Yaping designed a wearable all-carbon piezoresistive sensor that demonstrates high sensitivity (37.3 kPa^-1) and a wide linear range (0–1.4 MPa). Combining experimental data with finite element analysis, the team examined the cooperative effects between the sensing-layer microstructure and the elastic support, and characterized key performance metrics including sensitivity, sensing range, response time, and long-term stability. The device also shows superhydrophobicity, high breathability, and biocompatibility, and was evaluated for physiological monitoring, voice recognition, and two-factor authentication applications. The work was published in Advanced Functional Materials. Co-first authors are Xiang Qixuan (PhD student, Shanghai Jiao Tong University) and Zhao Guanjie (MS student, Columbia University). Corresponding authors are Zhao Yaping and Assistant Researcher Tan Huijun.
Fabrication and Materials Characterization
Based on studies of graphene-based carbon aerogel microtopology, the team used micro/nano 3D printing and epoxy resin transfer to make a detachable double-sided inverted pyramid mold. They then prepared a double-sided pyramid graphene-based carbon aerogel (DPA) sensing layer via rapid freezing, freeze-drying, and controlled pyrolysis. The sensor was assembled in a sandwich structure (DPA-ES@BCS) using the DPA as the sensing layer, a superhydrophobic graphene-nylon fabric (BCS) as the electrode layer, and an Ecoflex rubber frame as the elastic support (ES).
SEM and XRD analysis indicate that the graphene aerogel sensing layer has a regular micro-scale pyramid morphology and that the aerogel converts to a highly ordered graphitic structure after pyrolysis. The modified nylon fabric electrode has a superhydrophobic surface; after coating with an acrylic emulsion binder and transferring graphene powder, the graphene/nylon electrode has a low resistance of 5.2 ohm/cm, supporting high sensor sensitivity. The assembled DPA-ES@BCS sensor shows a water vapor transmission rate of 548.62 g m^-2 d^-1, better than a PDMS membrane at 376.06 g m^-2 d^-1, demonstrating effective gas exchange capability.
Sensing Mechanism
The team developed an equivalent circuit model to analyze the sensing mechanism of the DPA-ES@BCS sensor. With increasing pressure, the pyramid structures of the DPA compress, increasing the contact area between the sensing layer and the electrode and rapidly reducing contact resistance. Simultaneously, deformation of the DPA's porous internal structure generates additional conductive paths, markedly lowering the bulk resistance of the DPA. The combined effect yields high sensitivity (37.3 kPa^-1). The Ecoflex rubber frame provides mechanical support and, through its elastic behavior, extends the linear sensing range to 0–1.4 MPa. The sensor also exhibits high stability over 30,000 cycles, indicating reliability for long-term use.
Applications
In practical tests, the DPA-ES@BCS sensor can monitor a range of human physiological signals and activities in real time, including respiration, voice, and motion. The sensor performs well in voice recognition tasks, accurately distinguishing individual words and supporting pattern recognition with machine learning algorithms, which demonstrates stability for long-duration voice signal recording and potential for human–machine interaction in artificial intelligence systems. For information security, the team implemented a 4×4 sensor array (Figure 6) and demonstrated a two-factor authentication system that combines a traditional password with pressure-pattern input to enhance security.
Conclusion
This study combines a double-sided pyramid graphene-based carbon aerogel sensing layer, a superhydrophobic graphene-nylon electrode layer, and a high-elasticity Ecoflex rubber frame to distribute mechanical stress effectively and produce a piezoresistive sensor with both high sensitivity and a wide linear range. The all-carbon design improves chemical stability, breathability, and biocompatibility, making it suitable for wearable devices. The sensor's performance suggests potential across health monitoring, artificial intelligence, human–machine interaction, and information security applications.
