Flexible Medical Tattoo Heater Allows for Real Time Temperature Control

February 24, 2020

photo of nanshu luNanshu Lu, an associate professor of aerospace engineering, engineering mechanics and biomedical engineering, is part of a UT Austin research team that was selected by the journal Micromachines for the best paper award in 2019. The team was selected for its paper entitled "Stretchable Tattoo-Like Heater with On-Site Temperature Feedback Control."

Heat therapy plays an important role in the medical field and is used in a variety of different applications, including heat therapy for injured muscles and joints, controlled drug delivery through the skin and perioperative warming. Existing state-of-the art skin heaters are often bulky and rigid with limited long-term wearability. The more recently developed stretchable, wearable patch heaters are often expensive and time consuming to fabricate and also lack the ability to provide continuous, on-site temperature feedback control which is critical for most medical applications.

Lu’s team has developed, fabricated and tested a new wearable, stretchable tattoo-like heater that covers a large area of the skin, is ultra-thin and cost-effective. The wearable heater also measures real time temperature for extended periods of time and automatically adjusts to the target temperature using autonomous proportional-integral-derivative (PID) temperature feedback control.

To make the patch heater more cost effective and allow for quick fabrication, the device is made of a stretchable aluminum heater and a stretchable gold resistance temperature detector applied to soft medical tape. A cut-and-paste method is used to assemble the patch, which can be applied directly onto human skin, allowing for movement and flexibility while it is being worn.

photos of tattoo heater patch applied to a human hand opening and closing
Above: (a,b) The heater tattoo conforms to hand and maintains its conformability during opening and closing; (c,d) Infrared (IR) images of the device powered with proportional-integral-derivative (PID) control as the hand is opened and closed. The PID controller automatically adjusts power output so the hand does not overheat when it closes.

The team demonstrated with several tests that the device is capable of maintaining a target temperature over long periods of time while accurately adjusting to a new temperature when required. They say the cost of the device is so low that it could be considered for disposable use.

Learn more about Nanshu Lu’s research group on the Mechanics and Materials of Bio-Integrated Electronics website.