Rapid Fabrication of Liquid Metal Patterns for Stretchable Electronic Circuits

Stretchable circuits are crucial for the development of large-area electronics that can be used in wearable computing, soft robotics, and physical human-machine interaction. Gallium-based room temperature liquid metals (LMs) have emerged as a promising option for use as electrical conductors in soft and stretchable electronics. However, the lack of efficient and robust fabrication techniques has hindered the widespread use of LM electronics. Current methods typically require specialized equipment and cleanroom fabrication, which can be labor-intensive. To address this challenge, I have developed a facile and digital fabrication approach for creating LM-based circuit assemblies that can be interfaced with a broad range of substrate materials, from hyperelastic elastomers to spandex-blend fabrics. This method involves bonding a readily available and cost-effective copper (Cu) metal leaf to the substrate, which is then coated with LM. UV laser micromachining is used to pattern the biphasic Cu-LM film, a method commonly utilized in creating conventional printed circuit boards, by taking advantage of photophysical ablation. Off-the-shelf microelectronic components can then be directly interfaced with the Cu-LM biphasic film to create fully untethered circuits. The circuit connections between the Cu-LM biphasic film and microelectronic components are improved by a bulk HCl vapor treatment, which is only possible due to the Cu adhesion layer. I have demonstrated the versatility of this method with several implementations on a variety of substrate materials. The maskless, digital fabrication approach will enable rapid prototyping and fabrication of LM-based circuit assemblies, allowing for the creation of untethered on-skin electronics and biosensing devices without the need for cleanroom fabrication. This approach offers a low-cost, scalable, and efficient alternative to current fabrication methods, which could pave the way for more widespread use of LM electronics in soft and stretchable applications.