How Tiny 'Bunny' Helped Microscopic Object Research
Two microstructures made with the new material. Left: Pre-charring. Right: Post-charring.
CREDIT: Optical Materials Express.
It's not easy to make microscopic objects. It's even harder when you need that microscopic object to have specific properties, like the ability to conduct or store electricity.
But now researchers say they've developed a substance that can be used to make three-dimensional structures that are complex, conductive and extremely small.
The process of making electrodes involves carbonization, or "charring" a substance until its surface turns to carbon. Until now, the resins most commonly used in 3D shaping did not respond to carbonization and therefore could not be used in electronics. [See also: All-Natural 3D Printers: Salt and Wood Can Be Used]
The substance developed by graduate student Yuya Daicho and her colleagues at Japan's Yokohama National University is a resin, or a thick liquid that hardens into a solid. Examples of naturally occurring resins include amber and tree sap. This particular resin, however, has been diluted with a solution of resorcinol diglycidyl ether, which makes it respond to carbonization.
To demonstrate their technique, the researchers used the resin to reproduce the "Stanford bunny," one of the first digital 3D models created by scanning a real object—in this case, a ceramic figurine of a rabbit. The Stanford bunny represents a landmark in 3D modeling, and the Yokohama researchers' bunny is a highly faithful reproduction of the original, famous model — except that it's less than 30 micrometers long.
The new resin also works well with traditional methods of shaping 3D objects at a microscopic level. The first technique, called "microtransfer molding," involves using ultraviolet light to mold and then harden the resin. The second, called "two-photon polymerization," involves using a targeted laser to draw layered shapes directly into the resin, and then carbonize them.
Using these two techniques, the researchers were able to make several types of pyramidal and circular shapes about the size of a single bacterium, so small that they need to be viewed through a scanning electron microscope.
The resin could therefore have a huge impact in making highly customized microelectrodes for fuel cells or batteries — or even brain interfaces. These devices, which are used in deep brain stimulation and in treatment for brain-related disorders such as epilepsy, depression and Parkinson's disease, work by sending and receiving electric signals via microelectrodes. [See also: Look NASA, No Hands! Astronauts Fly on Brainpower Alone]
This resin will give scientists the ability to create more detailed and specialized devices.
The researchers' findings were published today (May 30) in the open-access journal Optical Materials Express.