Multilayered Electronic Tattoo Gets Amplified with the Crease Effect
Researchers have achieved multilayered electronic tattoos that can enable the crease amplification effect.
Researchers from the Capital Medical University’s Department of Biomedical Engineering have designed a multilayered, conformal, and sticky electronic tattoo that can stretch up to 800% and enable the crease amplification effect, which boosts an output signal by a factor of three. The team successfully created the electronic tattoo with a single heater and 15 strain sensors for temperature adjustment, movement monitoring, and remotely control robots.
Wearable medical devices and electronic tattoos have been around for a while and have been utilized by patients and athletes to monitor everything from heart rates to the amount of oxygen in the blood. While most of those health monitoring devices can conform to the skin using silicone substrates, they rarely are capable of adhering to human skin for prolonged periods. Repeated deformations and bending usually result in a loss of adherence between the skin and the tattoo, disrupting sensor signals. To overcome that issue, the engineers developed their METT (Multilayered Electronic Transfer Tattoo) using materials that can be embedded into small skin features such as finger creases and fingerprints and remain in contact with the skin, even with constant bending.
The METT was fabricated using three layers — an acrylic adhesive layer, a release layer, and circuits sandwiched between the two. The circuit layer comprises a thin polystyrene-butadiene-styrene (SBS) film with liquid-metal conductors and a series of strain sensors embedded into the material. The MPC provided excellent conductivity and stretchability to the device, while the SBS film supported the conductors and electrically isolated them in different layers.
The tattoo is applied via pressure with the release layer removed in the process, which bonds to the skin forming a secure attachment. The three-layered METT can monitor 15-DOF in the human hand, and the engineers demonstrated that human dexterity could be used to control a robotic hand as long as it has the same DOF.