New method could lead to cheaper electronic tattoos

Researchers from The University of Texas at Austin have developed a new method to produce “disposable tattoo-like health monitoring patches for the mass production of epidermal electronics”. The Cockrell School of Engineering Assistant Professor Nanshu Lu helped develop the technology in 2011.

Led by Lu, the team’s breakthrough is a repeatable ‘cut-and-paste’ method that cuts manufacturing time from several days to only 20 minutes. The researchers believe their new method is compatible with roll-to-roll manufacturing — an existing method for creating devices in bulk using a roll of flexible plastic and a processing machine.

Reliable, ultrathin tattoo-like wearable electronic devices have the ability to pick up and transmit the human body’s vital signals, tracking heart rate, hydration level, muscle movement, temperature and brain activity.

Although it is a promising invention, a lengthy, tedious and costly production process has until now hampered these wearables’ potential.

“One of the most attractive aspects of epidermal electronics is their ability to be disposable,” Lu said.

“If you can make them inexpensively, say for $1, then more people will be able to use them more frequently. This will open the door for a number of mobile medical applications and beyond.”

The UT Austin method is the first dry and portable process for producing these electronics, which, unlike the current method, does not require a cleanroom, wafers and other expensive resources and equipment. Instead, the technique relies on freeform manufacturing, which is similar in scope to 3D printing but different in that material is removed instead of added.

The two-step process starts with inexpensive, prefabricated, industrial-quality metal deposited on polymer sheets. First, an electronic mechanical cutter is used to form patterns on the metal-polymer sheets. Second, after removing excessive areas, the electronics are printed onto any polymer adhesives, including temporary tattoo films. The cutter is programmable so the size of the patch and pattern can be easily customised.

“These initial prototype patches can be adapted to roll-to-roll manufacturing that can reduce the cost significantly for mass production,” said Associate Professor Deji Akinwande. “In this light, Lu’s invention represents a major advancement for the mobile health industry.”

After producing the cut-and-pasted patches, the researchers tested them as part of their study. In each test, the researchers’ newly fabricated patches picked up body signals that were stronger than those taken by existing medical devices, including an ECG/EKG, a tool used to assess the electrical and muscular function of the heart. The team also found that their patch conforms almost perfectly to the skin, minimising motion-induced false signals or errors.

The UT Austin wearable patches are so sensitive that Lu and her team can envision humans wearing the patches to more easily manoeuvre a prosthetic hand or limb using muscle signals. For now, Lu said, “We are trying to add more types of sensors including blood pressure and oxygen saturation monitors to the low-cost patch.”

Image caption: Assistant Professor Nanshu Lu and her team have developed a faster, inexpensive method for making epidermal electronics. Image courtesy of Cockrell School of Engineering.