A little over a year ago, Rich Ranky was at Northeastern, working on research for his PhD about how to build a force-measuring sensor into a plastic component. Back then, Ranky was injecting conductive slurry into plastic pieces with a caulking gun. Now, his 3D printer, Donatello, prints patented sensors that measure temperature, vibration, heart sensors and electricity, all for a cost between $10 to $15.

Ranky spun his company, 3-Spark, out of Northeastern with professors Constantinos Mavroidis and Mark Sivak. He received $100,000 in seed funding from the University, and uses the school’s machine shops for most of his hardware development.

“I feel like Northeastern’s baby,” Ranky said, laughing. “They have been really, really good to me.”

Though he appreciates the exercise he gets from biking back and forth from Northeastern to MassChallenge, Ranky is lobbying the accelerator to install a machine shop somewhere in the building, perhaps in the new location at the Innovation Design Center. Until that time, things will continue to be a little chaotic for 3Spark, but not nearly as chaotic as the printer itself.

As Ranky explains the inner-workings of the printer:

There is a plastic deposition system which is the plastic laying down the housing and framework of the structure, and then there is the conductive deposition system—patent-pending—which is putting the conductive material down. However, you design it in the computer, the plastic goes through the layers and it will leave a channel half open and then with the motorized syringe, it offsets and squeezes the conductive material into the channel and the plastic continues building on top of it.

Basically, the plastic body of the sensor is printed layer-by-layer, sort of like a reverse shredder. As it builds it leaves a little gap, which is filled with conductive material resulting in what looks like a metal splinter.