3-D printing complex structures with conducting polymers

Conducting polymers combine flexibility, low cost, and electrical conductivity in a material that can be processed in solution. These properties drive manufacturers to use the materials in solar cells, flexible electronics, and other applications. Device makers might use these polymers even more broadly if it were easy to construct products with them using a wide variety of fabrication techniques. But flow properties and other factors typically limit engineers to using just a few tools, such as electron beam lithography and inkjet printing, when working with conductive polymers. Those techniques require multiple complex steps and are largely limited to forming 2-D products, however. Now, Hyunwoo Yuk and Xuanhe Zhao of the Massachusetts Institute of Technology, Baoyang Lu of Jiangxi Science and Technology Normal University, and coworkers developed a cryogenic freeze-drying method for transforming PEDOT:PSS, one of the most commonly used conductive polymers, into a paste-like ink that is well suited to 3-D printing (Nat. Commun. 2020, DOI: 10.1038/s41467-020-15316-7). Demonstrating its usefulness, the team used the ink to 3-D print 100 complex flexible circuits with micrometer-sized features in just minutes (shown, glove) and a multicomponent flexible neural probe for bioelectronic signal monitoring (shown, finger).