Session: 13-08-01: Mechanics and Materials of Soft Electronics I

Paper Number: 172685

High-Resolution Liquid Metal-Based Stretchable Electronics Enabled by Colloidal Self-Assembly and Micro-Transfer Printing 

Liquid metal-based stretchable electronics offer high electrical performance and seamless integration with deformable systems, but face challenges in achieving scalable, high-resolution patterning. In this work, we present a method for micropatterning liquid metal particle (LMP) films with feature sizes as small as 5 µm, by integrating electrostatically enabled colloidal self-assembly and micro-transfer printing. The resulting cold-welded LMP micropatterns exhibit exceptional electromechanical properties – high conductivity (2.4×10⁶ S/m), stretchability (over 1200%), and strain- and pressure-insensitive resistance, owing to their multiscale and dynamic morphologies. Demonstrations in highly stretchable strain sensors and cardiac mapping devices highlight the capabilities of this method for creating high-performance, highly stretchable electronic systems. Notably, balloon catheter-integrated LMP microelectrode arrays show low impedance under extreme deformations, and enable high-resolution endocardial electrogram mapping inside the human heart. This method expands the potential of liquid metal-based stretchable electronics for a wide range of applications, including implantable biomedical devices and soft robotics.

In summary, we have presented a micropatterning method that integrates electrostatically enabled colloidal self-assembly and µTP to form highly interconnected LMP thin films with distinctive electromechanical properties for stretchable electronics. The close packing, rupture, and coalescence of LMPs during the self-assembly and µTP processes result in unique LMP network morphologies, which are quantitatively explained through nanomechanical testing and analytical modeling. The LMP micropatterns achieve minimum feature sizes of 5 µm with a minimum thickness of 1.5 µm, an initial conductivity of 2.4×10⁶ S/m with stretchability over 1200%, representing some of the best performance among all liquid metal materials. The dynamically changing interconnectivity within micropatterned LMPs under varying strains leads to unusual strain-insensitive electrical properties. This combination of unique fabrication capabilities and material properties enables the creation of high-resolution stretchable electronics. These devices can seamlessly interface with soft tissues or compliant surgical tools for high-quality electrical and electrophysiological sensing, as demonstrated in strain sensing and cardiac mapping. The unique endocardial mapping capabilities suggest compelling opportunities for these high-performance stretchable electronics to interface with biological systems in a mechanically imperceptible manner. One limitation of the current approach is its reliance on interfacial adhesion between LMPs and the target substrate, which may affect the patterning quality. Future studies investigating interfacial adhesion across a wider range of materials could help enhance the versatility of this method. The liquid metal patterning method presented here may be applied to the creation of a wide range of bio-integrated systems, such as wearable and implantable biosensors, prosthetics, and neural interfaces.

 

 

Presenting Author: Hangbo Zhao University of Southern California

Presenting Author Biography: Dr. Hangbo Zhao is an assistant professor in the Department of Aerospace and Mechanical Engineering and the Afred E. Mann Department of Biomedical Engineering at the University of Southern California, working on micro- and nanomanufacturing, and bio-integrated electronics. Prior tojoining USC, he was a postdoctoral researcher at Northwestern University. He received his M.S. and Ph.D. degrees in Mechanical Engineering at MIT. Dr. Zhao has received several awards including the NSF CAREER Award, Office of Naval Research Young Investigator Award, the Society of Manufacturing Engineers (SME) Outstanding Young Manufacturing Engineer Award, and the ASME Haythornthwaite Foundation Young Investigator Award.

Authors:

Hangbo Zhao University of Southern California