Other than putting it in a tiny art gallery, what could you do with a rabbit sculpture that sits just a few micrometers tall? Perhaps not much, although it’s a remarkable example of the level of detail that can be achieved using a new electrically-conductive shapable resin. That same resin could find use in custom-formed electrodes for things like fuel cells, batteries, or even biosensor interfaces used to treat brain disorders.
Presently, when an electrode is created, it’s baked at a high temperature in order to turn its surface to carbon. This process is known as carbonization or charring, and it greatly increases the conductivity of the resin used to make the electrode. That said, in the same way that regular plastic items melt when exposed to heat, the carbonization process likewise causes resin electrodes to lose their shape.
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A team of Japanese scientists from Yokohama National University, Tokyo Institute of Technology and the company C-MET set out to create a resin that would retain its shape when carbonized. The photopolymer resin they came up with consists of a light-sensitive liquid combined with an epoxy known as Resorcinol Diglycidyl Ether (RDGE), the latter of which is usually used simply to dilute existing resins.
The scientists were able to form the resin into a variety of miniscule shapes (such as the Stanford bunny) in either of two ways – one form of the resin could be molded and then hardened by exposure to ultraviolet light, while another could have a shape “drawn” into it using a laser, causing only the laser-exposed liquid to harden in successive stacked layers.
In either case, when the microstructures were subsequently carbonized at 800ºC (1,472ºF), they shrunk but kept their shape. The amount of shrinkage could be predetermined by the concentration of RDGE used in the resin. This is actually advantageous, as it means that electrodes could be (slightly) more easily formed on a larger scale, and then shrank down for actual use.
The researchers now plan on seeing what happens when the resin is baked at higher temperatures. While the process may destroy the microstructures, it may also convert their surfaces into graphite instead of carbon, making them even more conductive.
A paper on the research was recently published in the journal Optical Materials Express.
Source: The Optical Society