MADISON – In the not-too-distant future, flexible electronics will open the door to new products like foldable phones, tablets that can be rolled, paper-thin displays and wearable sensors that monitor health data. Developing these new bendy products, however, means using materials like new plastics and thin films to replace the rigid circuit boards and bulky electronic components that currently occupy the interiors of cell phones and other gadgets.
New research by a University of Wisconsin-Madison engineer leverages a surprising and inexpensive substance – wood – to make the flexible microwave circuits that power modern communications.
In a paper published today in the journal Nature Communications, Zhenqiang “Jack” Ma, a UW-Madison professor of electrical and computer engineering, explains how he and his collaborators constructed a functional microwave amplifier circuit on a substrate of cellulose nanofibril paper, a wood product.
Microwave components, which are used in wireless communication, have proved difficult to produce in a flexible form and are typically constructed on integrated semiconductor chips or printed on circuit boards. But flexible versions, including thin-film transistors and other components Ma has been creating for more than a decade, could have widespread applications in wearable devices, drones and as part of large-area microwave arrays used in 5G wireless networks and advanced communication systems.
Previous attempts to produce flexible microwave amplifiers used rigid semiconductor-based integrated circuits that were thinned down and moved to flexible substrates – a cost-prohibitive approach.
In the new amplifier, Ma and his colleagues began with cellulose nanofibril paper as the substrate. In recent years, Ma has collaborated with researchers from the U.S. Department of Agriculture Forest Products Laboratory in Madison, and from the Wisconsin Institute for Discovery to assess the feasibility of using the material as a substrate for flexible electronic circuits. The paper is made by breaking wood fiber down into nanoscale fibrils, or tiny slender fibers, then recombining them to produce a strong, flexible, transparent and biodegradable film.