Probably many people are aware of the efforts by the electronics industry to make wearable or, at least, flexible electronics. Smartphones that could be folded in half like a piece of paper and put in a pocket would certainly be desirable. Eventually, they could even be included in clothing or, rather, clothing could be included in a smartphone.
The challenge in making effective wearables and other flexible electronics is almost entirely a materials-issue: Materials must be developed to provide identical functionality as those used in modern electronics but they must also be both flexible and durable, meaning that their potency diminishes with use and repeated folding no faster than a rigid electronic device. A consumer device might need a flexible touch-display or other interface of some sort, circuit elements, and a power supply at minimum. Probably we also want some form of contactless charging too, perhaps an integrated solar cell. This is a lot of functionality to re-engineer. On top of that, some papers have explored the ambitious goal of directly printing these materials as a fully-formed device from something as simple as an inkjet printer.
I report here my work on a material that may be a potential power supply for flexible electronics on paper or textile substrates. I was responsible for the synthesis and materials characterization of PEDOT films on nylon paper substrates. This involved using oxidative chemical vapor deposition (oCVD) processes developed in Gleason Group at MIT to deposit PEDOT from monomeric EDOT. Over the course of the project I performed various tests and experiments involving thermogravimetric analysis (TGA, to observe how stable the film was), differential scanning calorimetry (DSC, also to check for stability and other thermal properties), and lots of scanning electron microscopy (SEM, to perform elemental analysis on cross-sections and check for conformal coating of the CVD layer as well as general surface morphology).
A couple interesting problems came up while working with the SEM. We wanted to perform elemental analysis using energy-dispersive x-ray spectroscopy (EDX) but we noticed that a sulfur peak (sulfur indicating the presence or lack of PEDOT) lined up with a gold peak in the spectrum making it difficult to differentiate between the two. We had to start carbon-coating our samples instead of using the standard gold-palladium sputtering to get better elemental maps like the ones in the paper. Another problem we had in getting nice images of the cross-section was that cutting our paper samples with scissors or razor blades would crush the fine mesh structure of the paper and yield poor images. We tried using a focused ion beam (FIB) with mixed results but ultimately resorted to snapping our samples in cryogenic conditions.
Liu, Andong, Peter Kovacik, Nolan Peard, Wenda Tian, Hilal Goktas, Jonathan Lau, Bruce Dunn, and Karen K. Gleason. 2017. “Monolithic Flexible Supercapacitors Integrated into Single Sheets of Paper and Membrane via Vapor Printing.” Advanced Materials, 1606091. doi:10.1002/adma.201606091.
This work was performed at the Institute for Soldier Nanotechnologies and Gleason Lab under the supervision of Andong Liu and Karen Gleason.
