Two layes of wood are required, one coated with PDMS (polydimethylsiloxane) – that gains electrons upon contact – and the other run through with nanocrystals of ZIF-8 (zeolitic imidazolate framework-8), a metal-ion organic-molecule hybrid network that can lose electrons.
“Wood is basically triboneutral,” said scientist Guido Panzarasa of ETH Zürich and the Swiss Federal Laboratories for Materials Science and Technology (Empa). “It means that wood has no real tendency to acquire or to lose electrons, so the challenge is making wood that is able to attract and lose electrons.”
Of the types of wood tested, radially-cut spruce worked best, generating 24V open-circuit and 320μA short-circuit when pressed with 50N of force.
Output did not diminish up to 1,500 cycles.
“Our focus was to demonstrate the possibility of modifying wood with relatively environmentally friendly procedures to make it triboelectric,” said Panzarasa. “Spruce is cheap and available and has favorable mechanical properties. The functionalization approach is quite simple, and it can be scalable on an industrial level. It’s only a matter of engineering.”
The team’s next step is to find chemical coatings with similar function that are easy to use and more eco-friendly. “The ultimate goal is to understand the potentialities of wood beyond those already known and to enable wood with new properties for future sustainable smart buildings,” said Panzarasa.
Full information is available without payment in the paper ‘Functionalized wood with tunable tribopolarity for efficient triboelectric nanogenerators‘, published in Matter.