Some tattoos just look cool. Others save lives. 

Soon, doctors may use biological tattoos instead of blood pressure cuffs or thermometers to monitor vital organs. Nanshu Lu, assistant professor in the Cockrell School of Engineering, and her team have created an electronic device that doctors can implant directly onto patients’ skin. This technology could record bodily signals such as heart rate, glucose levels, hydration, oxygen levels and muscle movement. It can even measure brain waves.

“It’s multifunctional, multimodal,” Lu said. “And it’s thinner than a human hair.” 

Lu and her team created the current devices from metals, such as silicon and gold. They can design computer models of the patches in any desired shape and then immediately print them. These tattoos can then adhere directly to human skin. 

“They’re more similar to temporary tattoos than normal tattoos,” said materials science and engineering graduate student Luke Nicolini. “They go right onto your skin and can be removed in a week.” 

Because the devices are relatively easy to manufacture, Nicolini said they can be easily tweaked and improved.

“It allows us to try new designs on a whim,” he said. 

Current body monitoring tools are often large and cumbersome. Holter devices, which measure heart activity, are the size of a small camera. Patients can usually only wear them for 24–48 hours. Most accurate blood pressure cuffs do not allow for comfortable movement — patients usually only wear them at the hospital. 

“In the past, we could not put systems on the body very well,” Lu said. “That’s why you see that Fitbit fitness tracker or chest band. They’re not very comfortable, and, more importantly, they’re not accurate.”

Lu’s electronic tattoos more precisely measure vital signs because they adhere closely to skin. They allow for better data transfer over longer periods of time. The tattoos do not irritate skin like most monitoring devices do, which reduces redness and discomfort. The team is developing Bluetooth chips for this technology so it can move wirelessly. 

“If you have a chronic illness, and your doctor wants to check up on you, you can just wear this patch, and then you could use your phone to upload the data to the doctor,” Nicolini said. “Either the doctor or automatic analysis software can determine if something is going wrong.”

This technology could provide a quick and effective method of testing bodily systems, which has implications for health care and beyond. 

“Because it’s so cheap, it makes it affordable for entrepreneurs or small research groups,” said graduate student Rocky Yang, who studies aerospace engineering and mechanics. 

Nicolini is applying this technology in robotics for his graduate thesis. Nicolini places the stretchable sensing patches on people’s forearms to measure the strength of their grip. He then uses a computer model to analyze how much force is coming from the muscle signals. He plans to communicate this data to a robot hand, which can then grip with the exact same force as the human hand. 

“Obviously, we’re not the first people to invent controlling robots with your muscles,” Nicolini said. “The problem is that others have had to use conventional electrodes. While those are good for short-term, if you wanted to use the robot in a factory every day, you would either get very uncomfortable or have to switch your electrodes out constantly.” 

Nicolini said that while he is interested in the health care implications of the device, he finds the robotic aspects the most compelling. 

“I think that’s a really exciting aspect of humanity — not becoming cyborgs, mind you, but the improvement of the ability of exoskeletons, prosthetics to help people,” Nicolini said.