Preparation And Dynamic Stability Research Of Flexible Printed Circuit Based On Liquid Metal

Flexible printed circuit?FPC?is a printed circuitry with conductive materials arranged on flexible substrates,forming a conductive pattern.Unlike traditional rigid conductive materials,Gallium-based liquid metals?LM?possess low modulus and high conductivity simultaneously,becoming candidate conductive materials in preparing flexible circuits with dynamic stability.However,due to the high surface energy,low modulus and fast oxidation of liquid metals,it is difficult to balance the interaction,processability and conductivity when composed with polymer substrates.Besides,the dynamic stability mechanism of flexible printed circuits based on LM is still unknown.In this thesis,dynamically stable flexible printed circuits are prepared through the structural design of liquid metal micro/nano-particles?LMPs?,which enhance the interaction,processability and conductivity in conductive polymer composite.Meanwhile,the dynamic stability mechanism of flexible printed circuits based on LM is studied.In order to enhance the interaction and processability between liquid metal and polymer matrix,high-speed mechanical stirring is utilized to prepare LMPs/PU conductive ink?distribution of particle size is about 20?m?.Then the conductive ink was brushed on 3M VHB tape to obtain stretchable circuit?LM/PU-C?,of which the initial volume conductivity can reach 9000 S/m.It was found that LM/PU-C with 10vol%liquid metal content achieve best dynamic stability.The resistance change is R/R0<3 under to 500%strain and the cycle number is more than 1200 times.Besides,the characterization of dynamic stability shows that LMPs are orientated to maintain the conductive paths as the strain increases and stretching continues,which contribute to its dynamic stability.LM/PU-C shows brilliant performance in stretchable circuity with a LED and speaker under 500%strain,demonstrating its great potential for applications in stretchable electronics.Initial conductivity of LMPs is low because of the Ga₂O₃.Thus,the core-shell structural conductive particles?Ag@LMPs?were successfully prepared by in-situ electroless plating.The initial sheet resistance of Ag@LMPs can be controlled between0.17-180?/sq by adjusting the feeding ratio of silver nitrate.When the critical stress of Ag@LMPs reaches 500?N?Ag NO₃:LM=1:1?,the nano-silver shell ruptures and inner liquid metal releases,repairing the conductive path instantaneously.Furthermore,a flexible circuit utilizing Ag@LMPs?A-Circuit?is fabricated by screen printing,and exhibits outstanding stability and durability?R/R₀<1.65 after 10 000 bending cycles in a radius of 0.5 mm?.In addition,the resistance is almost unchanged after scratching,showing the dynamic stability and real-time self-repairing?self-repair process<200 ms?of A-Circuit.The high performance of the core-shell structural particles we prepared in this study will become one of the candidate conductive fillers to fabricate real-time self-repairing flexible circuit,such as NFC tags,flexible cables,and direct writing circuit.