Three-Dimensional, High-Resolution Printing of Carbon Nanotube/Liquid Metal Composites with Mechanical and Electrical Reinforcement.

The formation of three-dimensional (3D) interconnections is essential in integrated circuit packaging technology. However, conventional interconnection methods, including the wire-bonding process, were developed for rigid structures of electronic devices, and they are not applicable to the integration of soft and stretchable electronic devices. Hence, there is a strong demand for 3D interconnection technology that is applicable to soft, stretchable electronic devices. Herein, we introduce the material and the processing required for stretchable 3D interconnections on the soft forms of devices and substrates with high resolutions. Liquid-metal-based composites for use as stretchable interconnection materials were developed by uniformly dispersing Pt-decorated carbon nanotubes in a liquid metal matrix. The inclusion of carbon nanotubes in the liquid metal improves the mechanical strength of the composite, thereby overcoming the limitation of the liquid metal that has a low mechanical strength. The composites can be 3D printed with various dimensions: the minimum diameters are about 5 μm and have a breakdown current density comparable to that of metal wires.