Multi-Stimuli Responsive Reduced Graphene Oxide Patterned Azo-Liquid Crystalline Polymer Networks for Stretchable electronics with Tailored Morphologies.

초록

The concept of ‘kirigami’ has been largely interested in stretchable electronics because the kirigami patterned structure can increase degree of freedom for deformation beyond the intrinsic material limit. For untethered shape-reconfiguration of stretchable electronics, it is a considerable strategy that apply a programmable material, representatively azo-benzene functionalized liquid crystalline polymer networks (azo-LCN), as a flatform of stretchable electronics. In this presentation, we introduce facile coating process of patterned reduced graphene oxide (rGO) as well as integration of the patterned rGO along with shape-reconfigurable azo-LCN. The rGO patterned azo-LCN (azo-LCN/rGO) demonstrates about 500 % higher storage modulus of 6.4 GPa than neat azo-LCN (1.3 GPa) and the electrical conductivity of 380 S cm-1 at 4 times of rGO coating cycles. In addition, multi-stimuli (i.e. UV, NIR, focused solar ray, and direct heat) responsive actuation of azo-LCN/rGO is achieved by photochemical isomerization of azobenzene moiety in conjunction with coefficient of thermal expansion (CTE) mismatch via photothermal effects. In particular, the convolution of photochemical and photothermal effects provided enhanced actuation performance of the azo-LCN/rGO bilayer from the neat azo-LCN monoliths. Finally, the kirigami pattern allows the azo-LCN/rGO to endure a higher strain beyond the strain capacity of azo-LCN/rGO without permanent damages on their own body and deterioration of electrical performance. The kirigami-engineered azo-LCN/rGO demonstrated passive, active and hybrid types of shape-morphing under mechanical tension, UV, and simultaneous stimuli of UV and tension, respectively. Toward shape-reconfigurable and stretchable electronics, we demonstrate UV-induced shape-reconfiguration of the kirigami-engineered azo-LCN followed by 60 % of mechanical strain by tension without increase in electrical resistance.