If you think there’s too much hype surrounding 3D printing, perhaps that’s because you’re only thinking about plastic parts.

After all, there's only so much you can do with hard plastic, according to Michael McAlpine, professor at the University of Minnesota.

Instead, McAlpine asks: What if you could print electronics directly on your arm?

Using a lightweight Anycubic Linear Plus Delta Rostok 3D Printer, McAlpine and his University of Minnesota team fabricated inductive coils – and placed them on a free-moving human hand.

By advancing beyond plastic and successfully opening up the technology to electronics materials, the mechanical engineering professor believes his 3D printing method carries a broader, more useful appeal.

The “adaptive” approach combines real‐time feedback control and direct ink writing to fabricate devices on moving freeform surfaces — a hand, for example.

Temporary markers, placed on the skin, are registered by a 3D scan. The printer then uses software algorithms and computer vision to adjust to movements in real time.

Unlike 3D-printing inks that must solidify at high temperatures — potentially burning the wearer — McAlpine's specialized ink made of silver flakes cures and conducts at room temperature.

To remove the electronics, simply peel the device off with tweezers or wash it off with water.

According to the researchers, the adaptive 3D printing method could support new kinds of smart manufacturing, from advanced medical treatments to directly printed wearable devices.

McAlpine sees the technology as a “Swiss Army Knife,” small enough to load into a backpack and capable of producing whatever an individual needs — from electronics to biological cells.

“In our lab, you have one student who prints these semiconductor devices and then he’s done with his time on the printer. Then, the next student comes along and prints cells for spinal cord therapy – a completely different project on the exact same tool,” said the professor and study lead.

In addition to the creation of wearable electronics, the researchers additionally printed cell‐laden hydrogels on live mice, potentially creating a model for future wound-healing studies.

What do you think? Can wearable electronics bring 3D printing to the mainstream? Share your thoughts in the comments section.

McAlpine spoke with Tech Briefs this week. See excerpts from the interview below.

Tech Briefs: What kind of tools do you imagine being printed with this kind of technology?

Professor Michael McAlpine: For the demonstration, we made conducting electronics to create a coil that powered an LED. But, in the future, we could print the LED itself, or maybe we could print a solar panel on a wrist, or chemical biological warfare sensor on your arm.

Tech Briefs: Take me through how the 3D printer creates a device on the hand.

McAlpine: We develop this silver particle-based ink, which is silver flakes within a polymer matrix. The ink cures at room temperature, so you don’t have to heat up your skin to sinter it or make it conductive.

[The printer has] a needle or nozzle extruding the ink, so we don’t want to puncture the hand. We did a 3D scan on the back of the hand, so when we do the writing, we can conformably adjust and compensate for the hand’s topology.

Finally, we have two cameras on the printer that allow us to track the motion of the hand in order to print the conducting electronic device on the back of the skin.

Tech Briefs: What was the inspiration for the idea?

McAlpine: People have been interested in this concept of integrated electronics on the body, but we hadn’t seen anyone actually just take a 3D printer and directly print electronics on the body.

Tech Briefs: What is the level of acceptance you’ve seen regarding the integration of electronics with biology?

McAlpine: A lot people today wear smartwatches. If you look at a smartwatch, it is sort of an electronic device that is tethered to the body. It’s really still a rigid brick, just like your cell phone and your laptop. The problem is that the materials that go into making the smartwatch — glass, silicon — are all hard and rigid and brittle, whereas the skin is soft and flexible.

With this 3D printing application, you throw all that out the window, because we’re taking electronics and putting it in a completely different form factor. We’re taking it out of the electronics industry, out of the wafer, out of the box, and we’re putting it basically in a syringe, and printing the electronics like a tattoo directly on the skin.

You don’t have to worry about the wafers and the fact that they’re rigid; now it’s an ink that can be printed.

Tech Briefs: Is this kind of functionality what’s needed to make 3D printing a more mainstream technology?

McAlpine: I think this finally provides a kind of “killer app” for 3D printing. People are taking chips and putting them under the skin, which is probably not the most comfortable thing in the world. If you can write these conformal liquid electronics basically onto the skin using a 3D printer, that solves all kinds of problems.

I think it’s going to open up tons of applications, maybe in the military as a “Swiss Army Knife of electronics.” Soldiers can take it out of their backpack, and they can print devices on their body. I think little kids are going to buy 3D printers and print electronics all over their arms too. I think this is where 3D printing is going.

Tech Briefs: How do 3D printed electronics compare to traditional electronics?

McAlpine: What you sacrifice is performance. You’re not going to get a 2 GHz processor with a billion transistors on your skin, but that’s not what you need, right? If you want a 3 GHz dual core processor, you should keep that in the box. But if you want something that’s a simple solar cell or a simple display, or a more rudimentary device, then you can use the printer.

Tech Briefs: What is most exciting to you about this technology and what’s possible?

McAlpine: Everyone has been interested in 3D printing for awhile. When people say it's hype, it's only because they're using it to print hard plastic. No one wants to do that. Once you start opening up to these other materials, then the sky’s the limit.

What’s most exciting to me is that anything’s possible. People are waiting. We had the age of steel, and then the age of plastic, and then we had the age of semiconductor electronics, but what’s the next thing? I think this is the next thing, because we can do anything.

Do you agree? Is 3D printing wearable electronics "the next big thing?" Share your thoughts below.