Researchers from the Institute of Metal Research (IMR) of the Chinese Academy of Sciences have developed a flexible, dual-function, self-compensating sensor that can recognize gestures and perceive temperature simultaneously. This offers a simplified solution for multifunctional sensing in wearable electronics, intelligent robotics, and electronic skin.

The study was published in Advanced Functional Materials on May 22.

Flexible sensors that can detect multiple physical parameters, such as temperature and strain, are increasingly important for next-generation smart systems. However, conventional approaches typically rely on integrating multiple sensing units or different functional materials, increasing device complexity, thickness, and packaging difficulty. More fundamentally, within a single sensing unit, different physical signals, such as strain-induced resistance changes and temperature-induced resistance drifts, are often mutually coupled, which makes accurate, simultaneous readout challenging.

To address this issue, Prof. TAI Kaiping and his team proposed a self-compensation strategy based on a single Bi₂Te₃/polyimide (PI) flexible film. By ingeniously exploiting the two intrinsic physical properties of the Bi₂Te₃ film, its thermoelectric effect, which generates a voltage in response to a temperature gradient, and its piezoresistive effect, which causes electrical resistance to change under mechanical deformation, the researchers achieved effective signal decoupling. 

Using the thermoelectric voltage as an in situ temperature signal, the researchers were able to compensate for temperature-induced drift in the resistance-based strain readout. This strategy significantly suppresses temperature fluctuation interference in strain detection without requiring additional temperature sensors, extra functional layers, or complex multi-unit structures.

The researchers further demonstrated that the carrier concentration of the Bi₂Te₃ film is closely related to both its thermoelectric performance and its piezoresistive response. By tuning the carrier transport properties, they were able to simultaneously enhance the Seebeck coefficient and the gauge factor, thereby improving the performance of both sensing modalities.

To showcase the device's practical potential, the researchers integrated the flexible sensor onto a finger, creating a wearable, dual-parameter perception system that senses temperature and strain. The system successfully recognized different bending gestures of the finger through the strain signal while simultaneously sensing the temperature of touched objects through the thermoelectric signal. 

This work establishes a new platform of materials and devices for highly integrated, miniaturized, multifunctional sensors with promising potential applications in human-machine interaction, soft robotics, and smart prosthetics.

Temperature-strain sensing mechanism of the Bi₂Te₃/polyimide film. (Image by IMR)

Coupling relationship between piezoresistive and thermoelectric effects in the Bi₂Te₃/polyimide film. (Image by IMR)