Circuits on demand: Engineer prints electrical components on paper

(Phys.org) —One of humankind's biggest technological steps was the ability to print words on paper. Now, thanks to College of Engineering assistant professor Anming Hu, it's technology itself that is being printed.

Hu, of the Department of Mechanical, Aerospace, and Biomedical Engineering, has researched a way to print circuits on paper, the main impact of which could be a decrease in cost and an increase in portability for any number of devices.

"Being able to design the circuit you want and then print it out allows for more responsive designs, easier control, and lower costs," said Hu. "The ability to print out the exact circuit you need the moment you need it can revolutionize a number of things."

One of the biggest advancements made possible by the technology could be in the world of medicine.

Currently, endless numbers of people suffer from a disease or affliction that requires them to frequently check in with a doctor or conduct medical testing. Diabetics, for example, rely on daily finger pricks to test their .

With a paper circuit enclosed in a liquid-proof barrier, those same patients could one day have a sensor implanted in them that could not only detect when their levels were out of kilter, but also signal itself to release insulin into their body.

"Being able to have an enclosed waterproof system with its own power source would open up a lot of areas medically," said Hu. "Right now, the focus is on being able to make the lines that form the circuit smaller."

The easiest way to picture how Hu's system works is to think of an inkjet printer, but replace the ink cartridge with one that dispenses liquid metal.

Hu's team tested more than thirty different types of paper before realizing that standard inkjet paper worked as well as anything, and was cheaper than most to secure.

The metal they use, on the other hand, is anything but ordinary.

"We use silver to make the nanowire," said Hu. "It's still much cheaper than making the 'normal' way, and it holds up far better than copper, which has a tendency to oxidize too quickly."

Hu's team was able to fold the paper-thin circuit 5,000 times with a high level of functionality still intact, answering questions about the durability of the finished product.

While medical uses could have the most day-to-day impact for such circuits, their flexibility and ease of use means anything electronic could benefit.

"The global applications for this will drive development in a long-term way," said Hu. "For now we will focus on improving the mechanics of this new type of additive manufacturing, working on multiple-nozzle printing, things of that nature."

The research has already gotten plenty of attention, with the American Chemical Society journal Applied Materials & Interfaces publishing the team's work and several other scientific journals taking note.


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Citation: Circuits on demand: Engineer prints electrical components on paper (2014, November 27) retrieved 18 April 2019 from https://phys.org/news/2014-11-circuits-demand-electrical-components-paper.html
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Nov 27, 2014
Yes, but how do you lay the components on it?

Wires alone don't do much.

Nov 27, 2014
Can't you just be happy for scientific advancements?

Nov 27, 2014
Can't you just be happy for scientific advancements?


Can't I ask a question?

The headline says that they've managed to print electrical components on paper, yet the article doesn't say a single word about the components - only about the connecting wires.

An article titled "Engineer prints electrical components on paper" should have at least some information about it.

Nov 27, 2014
Yes, but how do you lay the components on it?

Wires alone don't do much.


From the work I've done on making circuit boards and modifying them with silver inks, I would say that it should be possible to "glue" components to the "printed circuit" traces with, at a minimum, one of the commercial silver-bearing adhesives. Although without specialized tools this might be tricky for the home user, at an industrial level it doesn't appear to be that big a challenge.

Nov 28, 2014
Yes, but how do you lay the components on it?

Like on many commercially produced circuit boards nowadays: with conductive glue.

If you structure the pathways appropriately (small circles where the legs of your component will be) then it's self-guiding.
As with any printer it should not be too hard to print several fluids, so printing small glue dots where the components will go should not be too tricky.

Although without specialized tools this might be tricky for the home use

If you don't have steady hands you can always do what many do with the regular perf boards: spread solder (in this case conductive glue) over the entire area and then just scrape away the part between the legs with a scalpel. It doesn't look pretty but it works.


Nov 28, 2014
Like on many commercially produced circuit boards nowadays: with conductive glue.


I'd like to see a commercial product that has components glued it. It sounds like it saves you a lot of manufacturing overhead from soldering it in place, but it doesn't seem very durable.

What kind of products are we talking of? Smart cards?

spread solder (in this case conductive glue) over the entire area and then just scrape away the part between the legs with a scalpel. It doesn't look pretty but it works.


How fast is the glue? If you have enough time to lay the components in by hand one at a time, it doesn't seem very effective for mass manufacturing, or is it activated by UV light, heat, other?

Nov 28, 2014
I'd like to see a commercial product that has components glued it.

During uni I did a practice semester at a company that glued their components on. That was back in 1995. I was designing small modules and repairing broken ones. Of the broken ones there were any number of problems - but the adhesive was not one.

How fast is the glue?

There are several types. Some harden fast (used on manufacturing line), and some are malleable until you harden them under heat (I think there are even some that use UV hardening, but I haven't worked with those).

If you have enough time to lay the components in by hand one at a time, it doesn't seem very effective for mass manufacturing

Mass manufacturing is almost never done by hand. You can get very cheap robotic workplaces which are far more accurate. Components come in feeder mechanisms (basically profiled tubes of plastic with thousands of ICs or whatnot stacked) which you just hook up to the workplace.

Nov 28, 2014
During uni I did a practice semester at a company that glued their components on. That was back in 1995. I was designing small modules and repairing broken ones. Of the broken ones there were any number of problems - but the adhesive was not one.


What sort of backplane were you using? How was the glue applied?

Just so you aren't mistaking solder paste for glue.


Mass manufacturing is almost never done by hand.


Some hand assembly is often required. I have worked in such a production line. The SMD components are laid by a pick & place machine but the larger components like electrolytic capacitors and large chokes are still soldered by hand because of the difficulty and cost of developing an automated through-hole soldering machine that would be flexible enough to deal with multiple different products. Some SMD components are also too large or delicate for pick & place and reflow.


Nov 28, 2014
I've written a paper on the topic of using paper circuits made with colloidal Silver nano-particle inks to make ultra light and biodegradable UAVs. During this project I made many prototypes and found that, at least in a prototyping application, conductive epoxies & glues were almost unusable in comparison to solder.

The surface tension from solder flow will inherently prevent solder bridges from forming whilst making a strong connection (as solder will naturally flow onto a components contacts). Conductive glue does not have this benefit and can make it *extremely* hard not to short pins on fine pitched components. Additionally the mechanical bond is often quite brittle.

In my consequent work to solve the problem of allowing solder flow onto the silver tracks, I became involved with a startup that produces a hobby level desktop printer that allows you to prototype circuits that you can then also solder to. Search 'Cartesian Co Argentum' if you are interested.

Nov 28, 2014
Just so you aren't mistaking solder paste for glue.

It was not solder paste. I think we used something like this
http://www.henkel...7427.htm
but at the time I wasn't particularly interested in what company or brand name it was - as I almost never had to use the stuff.

Nov 28, 2014
The surface tension from solder flow will inherently prevent solder bridges from forming whilst making a strong connection (as solder will naturally flow onto a components contacts).


Not only that, the surface tension between the pad and the component will automatically center the component on the pad because the molten solder will try to minimize its surface area. As long as you've shaped and masked the pads properly, this will auto-align the component, which is very important if you have ball grid array chips with hundreds of contacts underneath it, where you can't see or fix any faulty connections after the fact.

It's hard to imagine how you would apply glue to the bottom of a BGA chip and assure that it all makes contact without spilling or bridging, while ensuring that the chip lands exactly in the right place at a speed of thousands of components a minute.


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