The Spoils of 3-D Printing

From low-cost prosthetic limbs and food to medical tools and figurines, 3-D printing has changed the way people think about manufacturing. Websites, such as Thingverse.com, offer designs for a myriad of printable objects at no cost to the user. All one has to do is own a 3-D printer, which one can purchase for as little as a few hundred dollars.

Engineers at the Univ. of California, Berkeley, in conjunction with colleagues from Taiwan’s National Chiao Tung Univ., announced their achievement of printing useful electrical components, such as resistors, inductors, capacitors and integrated wireless electrical sensing systems. Their research paper, published in Microsystems & Nanoengineering, outlines their success printing a 3-D “smart cap” capable of monitoring the quality of perishable liquids, such as milk and juice.

“This 3D-printing technology could eventually make electronic circuits cheap enough to be added to packaging to provide food safety alerts for consumers,” said Liwei Lin, the paper’s senior author, a professor of mechanical engineering and co-director of the Berkley Sensor and Actuator Center. “You could imagine a scenario where you can use your cell phone to check the freshness of food while it’s still on the store shelves.”



According to the research paper, the authors set out to find a way to produce a 3-D printed item capable of acting as a conductor, which polymers are poor at. The employed technique used VisitJet EX200 plastic and VisiJet S100 wax combined with silver paste to achieve results. A ProJet HD 3000 3-D printer distributed the plastic and wax alternatively through its dual nozzles. Next, the wax was dissolved from the 3-D pieces via a mineral oil bath at 80 C. The silver paste was then injected into the hollow areas.

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According to Berkeley, the metal’s shape and design dictated its function as an electrical component. “For instance, thin wires acted as resistors, and flat plates were made into capacitors,” according to the university.

The components were then combined with a plastic milk carton cap in an attempt to monitor spoilage. The combination of the capacitor and inductor created a resonant circuit. By flipping the food package upside down, a small portion of liquid food is trapped inside the cap’s capacitor gap. Afterwards, the food package was left unopened for 36 hrs at room temperature, 71.6 F.

“The circuit could detect the changes in electrical signals that accompany increased levels of bacteria,” according to Berkeley. “Those changes were detected wirelessly using the smart cap, which found that peak vibration frequency of the room-temperature milk dropped by 4.3% after 36 hrs. In comparison, a carton of milk kept in refrigeration at (39.2 F) saw a relatively minor 0.12% shift in frequency over the same time period.”  

“The positive results indicate that (3-D) devices with embedded metallic components can open up a new class of applications in devices … that benefit from (3-D) structures with embedded metallic conductors,” the authors concluded.


Source:rdmag.com