Interdigitated electrodes based on liquid metal encapsulated in elastomer as capacitive sensors and triboelectric nanogenerators

Liquid metal interdigital electrodes encapsulated in elastomers may, due to their flexibility and stretchability, allow new design structures for capacitive sensing and triboelectric energy harvesting. Here the performance of skin-mounted elastomer-embedded interdigital liquid metal electrodes for detecting small objects and generate triboelectric energy is explored. Different modes of sensing and energy harvesting are explored. It is demonstrated that the electrodes can be used for capacitive sensing on solid and liquid objects of different geometry, for example in liquid level sensing on curved objects, less accessible by other non-elastic electrodes. It is also shown that the elastomer-embedded interdigital liquid metal electrodes can be mounted on human skin and generate energy when fingers are slapping or dragged across the electrode, thus allowing one to differentiate between such movements. It is shown that triboelectric nanogenerators based on interdigitated liquid metal electrodes embedded in elastomer can be used as elastically deformable structures that do not loose mechanical function, and can also be used as elastic membranes which transform mechanical into electrical energy when set into vibration. A considerable advantage of liquid metals embedded in elastomers is the ease with which failures can be fixed or how the geometry of the interdigitated electrode can be reassembled by simple cutting and gluing. It is shown that the two-dimensional triboelectric generator that can be cut in pieces and reassembled in three dimensions, thus providing a new method to build three-dimensional triboelectric nanogenerators.