An everyday piece of paper has been successfully transformed into a self-powered device, and there’s a lot of chemistry behind this paper-based electronic. In an effort to bring low-cost, flexible electronics to the market, a team of engineers at Purdue University in Indiana, US, have created a specially formulated spray deposition that can turn any piece of paper into a human powered interface – and the result is pretty impressive.
Creating An Omniphobic, Self-Powered Paper Device
Self-powered paper-based electronics (RF-SPEs) are gaining a lot of momentum in 2020 because of their environmental friendliness, low production costs, and greater accessibility. But it’s not easy developing an electronic device that’s made of paper. Not only are they highly sensitive to moisture and dust, they’re also battery-dependent and incompatible with mass production technologies.
The team of engineers at Purdue University have found solutions to all of these challenges with their latest RF-SPE innovation:
“We developed a method to render paper repellent to water, oil and dust by coating it with highly fluorinated molecules. This omniphobic coating allows us to print multiple layers of circuits onto paper without getting the ink to smear from one layer to the next one.”
Ramses Martinez, Assistant Professor at Purdue’s School of Industrial Engineering
The new paper-based electronic developed at Purdue University has two main features:
- Omniphobic: The chemical coating used to create the device makes any paper-based substrate repellant to virtually all liquids and oils, as well as dust
- Self-powered: When someone uses this device, their finger-tapping creates friction between the layers of coating. As a form of triboelectric power, this generates around 20 volts
Using new printing technology, a bespoke chemical coating, and triboelectric power generation, these engineers have developed the first paper-based electronic that’s powered by human touch. It has the potential to transform any piece of paper or cardboard into an electronic interface, such as a numbered keypad, a music player, or even interactive packaging labels.
The Chemistry Behind RF-SPEs
When developing the chemistry behind this paper-based electronic device, the main goal was to create a chemical coating that had omniphobic properties and wouldn’t break up the substrate. The solution – literally – was a mixture of highly fluorinated molecules that repelled water, oils, and dust, without changing the look or feel of the paper.
Collaborating engineer Marina Sala de Medeiros says in her paper that the chemical coating is applied through sequential spray deposition of the following compounds:
- Alkylated organosilanes
- Conductive nanoparticles
- Ethyl cellulose
The most noteworthy chemical used in this RF-SPE coating is polytetrafluoroethylene (PTFE), otherwise known by the brand name Teflon. Perfluorinated chemicals, like the ones used in Teflon, have properties that make them well-suited to RF-SPEs: they’re non-wetting, very slippery, chemically inert, and non-stick.
How Does It Work?
By formulating a Teflon-like chemical coating, de Medeiros and her colleagues facilitated the creation of an omniphobic paper-based keypad that’s easy to print on and compatible with most large-scale mass production processes. Here’s a quick step-by-step on how it all works:
- The chemical coating is applied as an aqueous solution to the surface of the paper
- A template of an electronic circuit is placed on the back of the paper
- This is sprayed with two layers of material containing tiny nickel particles, which carry the electricity
- Another coating of the omniphobic formula is then added seal everything in place
- The paper is now ready to have graphics printed on, like a keypad of numbers
- A bluetooth chip is added so that the paper device can connect to computers
So, when someone uses this RF-SPE, the pressure from their finger will cause the layers of nickel to rub together and generate power along the printed circuit, directly to the bluetooth chip. Pretty great, right?
What Are The Benefits?
In a nutshell, this breakthrough technology will be able to transform paper or cardboard into completely wireless interfaces. For the engineering team at Purdue University, the biggest benefit of this paper-based electronic is its potential for smart packaging:
“I envision this technology to facilitate the user interaction with food packaging, to verify if the food is safe to be consumed, or to enable users to sign the package that arrives at home by dragging their finger over the box to properly identify themselves as the owner of the package.”
Aside from its usage, this new technology could also revolutionise the electronic devices industry by providing a low cost, environmentally friendly alternative to expensive electronics. Luckily, this paper-based technology has several benefits that can help realise this goal:
- RF SPEs are incredibly cost effective, costing around 25¢ per device – that’s about 19p
- They’re compatible with mass production technologies and printing processes
- RF SPEs are also completely foldable, making them very flexible and easy-to-carry
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