Development of a laser induced graphene (LIG) and polylactic acid (PLA) shape memory polymer composite with simultaneous multi-stimuli response and deformation self-sensing characteristics

Abstract

This study presents the integration of laser-induced graphene (LIG) on a polylactic acid (PLA) substrate to create a novel shape memory polymer composite (SMPC) with multi-stimuli response and deformation self-sensing characteristics. The LIG was initially engraved on a commercial polyimide film and subsequently transferred to the PLA substrate through hot compression. Raman spectra analysis confirmed the successful engraving of the LIG, exhibiting the typical characteristic peaks. Durability tests revealed that the transferred LIG adhered well to the PLA substrate. Additionally, the transferred LIG demonstrated a sheet resistance of 40.3 Ω sq⁻¹, which facilitated the electrical actuation of the LIG/PLA composite through Joule heating, allowing precise temperature control by manipulating the applied electrical power. An optimum electrical power of 0.95 W was identified to rapidly reach the actuation temperature without exceeding 80 °C. The study also demonstrated the LIG/PLA composite's responsiveness to infrared (IR) light, attributed to photothermal conversion behavior of LIG. An optimum IR intensity of 85 mW cm⁻² was established for reaching the actuation temperature without surpassing 80 °C. This multi-stimulus functionality was achieved alongside real-time monitoring of the shape recovery ratio, enabled by the piezoresistive properties of LIG, which allowed for recording electrical resistance changes during recovery. This approach eliminates the need for external components and offers a straightforward fabrication process. The ability to actuate and sense deformation using a single, integrated LIG pattern opens new opportunities for developing advanced, multi-responsive, and self-sensing shape memory polymer composites.