Liquid metal interfaces for component mounting on kirigami stretchable substrates

This study demonstrates liquid metal as an electrical interface material (LM-EIM) for mounting rigid electronic components on kirigami-based stretchable substrates. Kirigami structures impart high stretch tolerance to sheets made of materials with low stretchability through local bending and twisting. However, this advantage can be lost when rigid components are mounted using rigid EIMs, such as solder or conductive adhesive, because they mechanically constrain kirigami deformation and cause fracture at low strains. The LM-EIM itself exhibited high stretch tolerance, 24 and 35 times those of solder and adhesive, respectively. This highly deformable LM-EIM reduced constraints on kirigami deformation and suppressed fracture. Mounting with solder and adhesive reduced the substrate stretch tolerance to 32% and 36% of that without components, respectively. In contrast, mounting with the LM-EIM did not reduce the substrate stretch tolerance. The substrate fracture strain reached 3.99, corresponding to 1.1 times that without components. Finally, a resistor array maintained electrical connectivity up to a device strain of 2.0, while an LED array operated stably up to 1.5. This approach allows rigid, high-performance components to be integrated onto highly stretchable kirigami sheets without sacrificing their stretchability, enabling the development of high-performance, multifunctional stretchable electronics.