UC Berkeley researchers have developed 3-D-printed technology that allows for customizable microelectronics that can be used to detect spoiled milk.

New innovations in 3-D printing processes that can facilitate more microelectronic developments could increase the functionality of 3-D-printed products and allow for more customizable technology, according to the researchers.

By using an epoxy-like material and wax in the printing process, researchers were able to eventually melt the wax into microchannels, which were then filled with liquid metal. This process, using the 3-D printers, allowed for the creation of simple resistors and capacitors.

According to co-lead researcher Chen Yang, who worked alongside Sung-Yueh Wu from National Chiao Tung University, the development of future microelectronics using 3-D printing could allow for more qualitative observations of products, such as spoiled milk.

“The milk cap was just a fun little demonstration,” said involved campus graduate student Casey Glick. “The core of the project is to make 3-D-printed parts and incorporate metal and electronics.”

The project was developed using a high-resolution, multi-jet 3-D printer that can use two types of materials, wax and epoxy, and print at a definition as small as 70 micrometers, or about three-thousandths of an inch. While printing at such a high definition can take longer than other plastics-development processes, it allows for easy product customization, Glick said.

“3-D printing is very good for making customized products, and it’s all very simple to develop,” Yang said. “When you put microelectronics into it, it can improve the product a lot and tell you what’s going on in it.”

By allowing a small amount of milk between the capacitors within the cap, the installed microelectronics can monitor resonance-frequency changes, which result from increasing amounts of bacteria.

According to Yang, the cap may be incorporated into future manufacturing procedures; he will be meeting with a manufacturer next week. This technology may work in conjunction with radio-frequency identification technology, which uses small antennas on devices that can scan and track products, Yang said.

The new 3-D printed microelectronics could be used to keep track of products’ values — such as bacteria count or acid levels — that could then be recorded using the radio-frequency identification technology, he said.

The “smart caps” may provide a solution to food-waste problems caused by “sell by” dates, according to Glick. Being able to directly test the quality of milk and other products to see if they have spoiled would allow stores to continue to sell food as long as it is fresh and would prevent consumers from prematurely throwing food out.

According to professor Liwei Lin, who advised the research, the cap could be used to collect information that could later be read by a smartphone or other device. The technology is readily available, but the price may be too high because 3-D printing is not yet used for mass production, Lin said. The key technology that’s missing, according to Lin, is adding metallic structures to the current 3-D-printed plastic structures.

Contact Trevor Greenan at [email protected] and follow him on Twitter at @trevor_greenan.