Researchers at Zhejiang University in China have developed a method of printing flexible electronic circuits onto textiles and other surfaces using recyclable liquid metal microgel (LMM) ink.

They have demonstrated how the ink can be used to directly print an NFC antenna onto an item of clothing and identified other potential use cases, including the printing of smart electronic clothing for health monitoring and human-computer interaction.

The researchers used gallium-based liquid metals that are “considered ideal conductive components for flexible electronics” in combination with alginate microgel shells, to create an ink that possesses “excellent printability and superior adhesion to various substrates” and overcomes problems of “huge surface tension and poor wettability [that] hinder the patterning of LMs and their wider applications”.

“Although patterns printed with the LMM ink are not initially conductive, they can be activated to recover conductivity by microstrain (<5%), pressing and freezing,” the research team explains.

“Additionally, the activated LMM circuit exhibits superior joule heating behaviours and electrical performance in further investigation, including excellent conductivity, significant resistance response to strain with small hysteresis, great durability to non-planar forces and so forth.

“Furthermore, smart electronic clothes were fabricated and investigated by directly printing functional circuits on commercial clothes with the LMM ink, which integrate multiple functions, including tactile sensing, motion monitoring, human-computer interaction and thermal management.”

• This article was updated on 15 March 2022 to clarify that the researchers’ technology enables NFC antennas to be printed, but not entire NFC tags.

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