Interfacial charge phonon coupling in Bi₂Se₃/WSe₂ nanohybrids for bifunctional near-infrared devices

Photodetection and photomechanical actuation are essential for next-generation optoelectronics and soft robotics, yet their integration within a single device remains challenging. Herein, we report a bifunctional Bi₂Se₃/WSe₂ nanohybrid platform capable of simultaneously sensing and mechanically responding to near-infrared (NIR) light over a wide range of intensities. The nanohybrid is deposited onto polycarbonate filter paper via a vacuum-assisted self-assembly process, forming a flexible composite layer that combines efficient NIR absorption with a high thermal response coefficient. Leveraging the coupled photoelectric and photothermoelectric effects, the device exhibits dual operational modes. Under low NIR irradiation, it functions as a photodetector, delivering a responsivity of 6.03 mA W^-1, a detectivity of 0.61 × 10¹⁰ cm Hz^1/2 W^-1, and a fast response time of 0.93 s. As the incident light intensity increases, the device switches to a photothermal actuation mode, producing large-amplitude and reversible bending motions with maximum angles of 70°. A range of actuation behaviors, including autonomous light tracking, a push-up weightlifter, a soft robotic gripper, and spider-like phototropism, are demonstrated, highlighting the device's versatility and programmability. This multifunctional Bi₂Se₃/WSe₂ nanohybrid system offers a compact, contact-free, and scalable strategy for integrating sensing and actuation, providing new opportunities for adaptive optoelectronic devices and intelligent soft robotic systems.