Go from design to physical circuit board in three minutes with “smart film”

A prototype of the Printem copper film on a cloth substrate.

Frustrated with the often week-long turnaround on the assembly of a printed circuit board (PCB), two University of Toronto engineering students have created a process that allows users to create functional circuit boards in minutes using a common desktop printer.

Created by Varun Chadalavada and Gowtham Ramachandran, Printem works similarly to the Polaroid film that inspired the UofT duo. At its heart, the process relies on a flexible, photosensitive copper-based film. To design the desired conductive traces, users print a negative image of their circuitry onto the Printem film using a standard desktop printer.

The black ink acts as a mask; when the film is exposed to UV light, a layer of photosensitive adhesive sticks the desired pattern to the film’s bottom layer. Peeling away the film’s top layer leaves behind the copper circuit on the film’s plastic substrate, which can then be shaped with scissors to fit the application.

From there, the pair says the result is as functional as any standard PCB. Components can be affixed with solder or conductive glue. Most importantly, the copper traces are as conductive as conventional PCBs and much more so than conductive inks or other prototyping processes. Printem circuits are also quick to create, taking only the design and printing time, plus two minutes of UV exposure.

“We were heavily inspired by polarized film and the whole photolithography process of making things so we wanted to aggregate the benefits of both,” explains Chadalavada. “We invested as much functionality or “smartness” into the material itself as possible so that applications can be as complex as you want them, but everything about the design and using the product are straightforward and widely available.”

Currently, Printem is still in the prototype stage. While the photosensitive copper film is complete, the pair say they want to make the process as straightforward and reliable a possible. Toward that tend, the Printem team have created a box-like device that removes the need for the printing step. When connected to a computer, an LCD screen inside the box projects the desired circuit design onto the film using UV light.

“All the user needs to do is insert our film into our exposure device,” says Ramachandran. “It’s about size of the box an iPhone is shipped in and will have a slot where the film can be inserted. In a minute, the film will pop out with the functional circuit pattern.”

The original Printem prototype being used on a desktop printer.

While quickly printing PCB prototypes is a boon for electrical engineering tinkerers like themselves, Chadalavada and Ramachandran say Printem’s real potential is in making the process “substrate agnostic.” In this way, users could affix copper traces to any surface, even flexible ones like fabric or skin. In addition, the UofT pair says their process could employ materials other than copper.

“We’re starting with copper because we see a huge need in the rapid prototyping space to create circuits which is largely underserved,” Chadalavada says. “But, eventually, we can use the exact same technology and process with different functional materials like OLED. As an end user, without any engineering experience, you could print a design with OLED material, create a display or patterned light with different colors and deploy it anywhere like a sticker.”

Currently, Printem has earned a top spot on the James Dyson Award top 20 international shortlist, which puts them in the running for winning title and the $50,000 grand prize.
www.printem.io
www.jamesdysonaward.org