Pencil–paper on-skin electronics

Significance On-skin electronics are usually fabricated by patterning conventional inorganic materials, novel organic materials, or emerging nanomaterials on flexible polymer substrates. Consequently, the state-of-the-art on-skin electronics usually suffer from expensive precursor materials, costly fabrication facilities, complex fabrication processes, and limited disposability. By using widely accessible pencils and papers as tools, we have developed a variety of cost-effective and disposable on-skin electronic devices, ranging from biophysical sensors and sweat biochemical sensors to thermal stimulators, humidity energy harvesters, and transdermal drug-delivery systems. Also, pencil–paper-based antennas, two-dimensional and three-dimensional circuits, and reconfigurable structures are demonstrated. The enabled devices can find wide applications particularly in low-resource environments and home-centered personal healthcare owing to their low-cost resources, handy operation, time-saving fabrication, and abundant potential designs.