Chemical Exchange Between Silica Networks and Liquid Metals for All-Inorganic, Sintering-Free and Highly Conductive Inks.

Electrically conductive inks with noble metals (e.g. silver particles) and inorganic carriers (e.g. glass powder) are broadly applied in the electronics industry. However, such inorganic inks are generally not compatible with highly flexible electronics due to the inherent rigidity and poor surface compatibility. Based on the unique chemical exchange between silica hydroxyl groups and liquid metal surfaces, this work reports a wholeinorganic LM-silica gel ink (LMSG) with high electrical conductivity, excellent thermal stability, high flexibility, and surface compatibility. The conductive percolation threshold of the LMSG inks is only 43 wt.%, which is the lowest among reported LM composites so far. Interestingly, inorganic LMSG inks do not require any sintering procedure for conductive paths, removing serious constraints over traditional LM inks. In addition, LMSG inks can be prepared in bulk as powders for long-term storage (>1 year) by simple dehydration, and more importantly, the dehydrated powders can conveniently regenerate LMSG inks via re-dissolution. The circuits fabricated from LMSG inks show much improved thermal stability (>300 °C) compared with conventional LM inks (<100 °C). LMSG ink exhibits wide surface compatibility with plastics, wood, skin, etc. Highly flexible and complicated integrated circuits with microcontroller units (MCUs) can be successfully fabricated.