A laser-induced graphene/PDMS composite sensor with a dual structure enabling high-sensitivity under micro-strain and extended-range sensing

Abstract

Flexible sensors in practical applications are required to show sufficiently high sensitivity over wide sensing ranges; however, there always exists a trade-off. Herein, we address the aforementioned challenge through geometric innovation of laser-induced graphene (LIG) conductive paths. A liquid benzoxazine (PGE-fa) precursor is developed to enable in situ LIG fabrication on PDMS substrates, eliminating the conventional transfer-induced defects. Furthermore, a dual architecture integrating straight and serpentine LIG patterns in parallel synergistically resolves the sensitivity-range paradox, where the straight segments bear high sensitivity (GF = 68.98 at 1% strain) for micro-strain detection (0.05–10%), while the serpentine components maintain conductivity for large-strain tolerance (up to 30%). It is revealed that the cracks appear in the straight LIG line under small deformations, resulting in resistance change to guarantee high sensitivity, whereas the serpentine LIG line can dissipate stress through in-plane bending and rotational deformation and, therefore, contribute to the conductive path to accommodate extended strain range. In addition, the sensor exhibits exceptional performance in terms of rapid response/recovery (180/200 ms), an ultralow detection limit (0.05% strain), and 5000-cycle durability. Experimental validations in pulse waveform analysis, blink detection, joint motion monitoring, and Morse code-based human-machine communication collectively demonstrate the sensor's versatility across diverse physiological and biomechanical sensing scenarios. It is believed that the intelligent structural design in this work is attractive for the development of high-performance wearable systems in personalized healthcare.