As wearable electronics continue to evolve, there's growing interest in flexible and highly responsive pressure sensors that can detect subtle mechanical changes. These sensors are of interest in a range of applications, from motion tracking and physiological monitoring to human-machine interfaces and soft robotics.
Of the available sensing mechanisms (capacitive, triboelectric, and piezoresistive), the piezoresistive type stands out for its straightforward structure, easily processed signals, and simple integration into wearable systems. However, most flexible piezoresistive sensors still suffer from limited sensitivity and performance instability, making them unreliable for real-world use.
Biomass-Based Aerogels
Looking to address these issues, researchers have been exploring carbon aerogels derived from natural biomass such as cellulose, chitosan, and sodium alginate. These materials can offer ultralight weight, good electrical conductivity, large surface area, and mechanical resilience, all while being biodegradable and environmentally friendly.
However, these aerogels are limited by their energy-intensive manufacturing processes, such as high-temperature carbonization. Further, post-processing steps like dip-coating and electroplating often lead to non-uniform conductive pathways and weak interfaces, reducing sensor performance and scalability.
Drawing inspiration from cat whiskers, a study published in Advanced Functional Materials presents a new class of wearable pressure sensors that mimic the sensitivity and signal amplification mechanisms of cat whiskers.
In cats, whiskers are embedded in follicle-sinus complexes that convert subtle mechanical input into amplified neural signals, enabling exceptional spatial awareness. The researchers replicated this structure with biomass fiber aerogels (BFAs) made from hemp fibers in a sodium alginate matrix, aiming to enhance signal output by mimicking the sinus cavities of cat whiskers.
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Materials, Fabrication, and Testing
To construct the sensors, the team used long, strong hemp microfibers as a sustainable material with high mechanical strength. These fibers were uniformly coated with polyaniline to enhance conductivity, durability, and interfacial adhesion.
The coated fibers were then mixed with sodium alginate to form a lightweight, porous aerogel via a precursor-assisted in situ polymerization method, followed by freeze-synergistic assembly. This method ensured a well-distributed conductive network and structural integrity without relying on high-energy or chemically aggressive treatments.
The aerogels were then characterized, and their performance was evaluated. Field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray spectroscopy (EDS) were used to observe microstructure and confirm elemental distribution. Chemical composition was analyzed using Fourier transform infrared spectroscopy (FTIR), while thermal stability was measured through thermogravimetric analysis (TGA).
Mechanical properties under compression and tension were tested using a universal testing machine, and real-time electrical responses were recorded using a computer-controlled electrometer. To assess biocompatibility, the sensors were tested on L929 mouse fibroblast cells.
Performance Highlights and Potential
The resulting BFA sensors exhibited a high sensitivity of 6.01 kPa-1 and a rapid response time of 255 milliseconds. They retained stable performance after 500 compression cycles, maintaining a sensitivity of 7.24 kPa, and functioned reliably across varying load rates from 20 to 300 millimetres per minute.
The sensors were able to detect subtle physiological signals, such as carotid pulses and fine joint movements. They demonstrated potential in practical use cases, including Morse-code-based communication and handwriting recognition. These capabilities position the sensors as promising tools for real-time athletic performance tracking, rehabilitation, and interactive human-machine systems.
A Sustainable Path Forward
By mimicking cats' sensory systems, whiskers, and using sustainable, bio-based materials, the researchers have introduced a scalable and cost-effective approach to building highly sensitive pressure sensors. Their method avoids high-energy inputs and complex processing steps, making it an efficient technique for developing wearable electronics for health monitoring, intelligent interaction, and sports analysis.
Journal Reference
Xie, D. et al. (2025). Cat-Vibrissa-Inspired Biomass Fiber Aerogels for Flexible and Highly Sensitive Sensors in Monitoring Human Sport. Advanced Functional Materials, e12177. DOI: 10.1002/adfm.202512177, https://advanced.onlinelibrary.wiley.com/doi/10.1002/adfm.202512177
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