Fast-printed laser-induced-graphene pattern enabling directional thermal manipulation

Abstract

Thermal metamaterials have recently attracted extensive attention for capable of manipulating heat flux, which makes it a great application potential in the field of electronic devices. However, developing a thermal manipulation device with facilely fabrication remains challenging as according to the theory of transformation thermotics, it not only needs to judiciously design and precisely distribute multiple materials with distinct thermal conductivity (k), but also should strictly match the background material. Herein, a facile fast-printed UV laser process is proposed to fabricate high-resolution laser induced graphene (LIG) patterns with controllable thermal conductivity enabling directional thermal manipulation—two types of thermal meta-devices, thermal cloak and concentrator. Effective anisotropic thermal conductivities are achieved by alternately assembling multilayer LIG films with polyimide (PI) layers. To obtain the optimal design of the LIG based meta-devices, the effects of k of the LIG, width ratio r, the number of layers n, and the overall size on thermal manipulation are theoretically simulated. The film thickness and k of LIG under different laser parameters were explored, and it was found that the film with a suitable laser power and a smaller thickness expansion can achieve a higher k. Besides, the thermal profiles of LIG-based meta-devices are experimentally demonstrated with varying laser powers and scanning speeds. The experiment result shows that the LIG-based multilayer cloak and bilayer cloak exhibit temperature gradients as low as 0.18 and 0.169 K/mm at the center of cloaks, with k of 8.96 and 13.05 W m−1 K−1, respectively. Additionally, a method of sputtering a layer of Cu film on the surface of the LIG based thermal concentrator to improve its thermal conductivity has also been evaluated. More importantly, LIG films feature with a thermal conductivity tunable, high-resolution, cost-effective, rapidly and facilely fabrication method. The fast-printed LIG periodic multilayered structures construct a new thermal metamaterial that provides a viable approach to the thermal manipulation in electronic devices.