Smart Tattoos : Making their Mark on the Future of Healthcare Wearables

March 13, 2024

Photo from University of Texas

Wearable technologies designed for health purposes offer mobility, portability, and convenience, allowing users to utilize them in the comfort and privacy of their own homes. However, a new trend is emerging, shifting the focus from traditional wearables to tattooed wearables, making healthcare a seamless part of one’s skin.

Graphene: skin-like wonder material

In 2018, scientists developed skin-like electronic tattoos capable of real-time monitoring of health parameters such as blood pressure and body temperature. These graphene-based tattoos, originating from Tsinghua University in China , are highly flexible and conductive, making them suitable for various applications, including adherence to skin, masks, and throats for measuring body signals like breathing and heartbeat. Laser scribing technology allows for personalized patterns, enhancing potential commercialization.

Smart pigments and circuits

Researchers frorm the Imperial College London, led by Dr. Ali Yetisen, collaborated with scientists, engineers, and designers to develop “smart tattoo” pigments capable of monitoring biomarkers within the body. These pigments, replacing traditional tattoo ink with functional materials, change color in response to various stimuli, such as glucose levels or radiation exposure. Similarly, Dr. Carson Bruns at the University of Colorado Boulder explores smart tattoos to monitor external factors like UV light exposure, aiding in skin cancer prevention. Bruns’s work has led to the creation of a company called Magic Ink, aiming to commercialize these technologies. Despite potential benefits, challenges remain in public acceptance and accuracy of data. However, experts foresee a future where smart tattoos play a significant role in healthcare, offering personalized, proactive insights into health and wellness.

Photo from Carnegie Mellon University

Along the same vein, Researchers from Carnegie Mellon University and the University of Coimbra, Portugal, have developed a cost-effective method to create durable, highly flexible tattoo-like circuits for wearable computing. This involves adding small amounts of a conductive liquid metal alloy to tattoo paper, which can be easily applied to the skin using water, similar to children’s temporary tattoos.

Unlike other tattoo-like electronics, which often require complex fabrication processes or lack the necessary material performance, these circuits maintain functionality even under extreme bending and stretching, mimicking the properties of lightweight fabrics. The breakthrough technique, which involves inkjet printing of silver nanoparticle patterns sintered at room temperature using gallium indium alloy, is compatible with thin-film and heat-sensitive substrates.

These ultrathin tattoos have potential applications in epidermal biomonitoring, soft robotics, flexible displays, and 3D-transferable printed electronics. The research findings were published in Advanced Materials.

Touchable innovation

Among the plethora of wearable electronics that have sprung up since then, recently, researchers from the Italian Institute of Technology (IIT) led by Arianna Mazzotta and Virgilio Mattoli, developed an ultra-thin wearable device capable of replicating localized sensations of touch. Its potential uses, according to the researchers, include providing sensory feedback to amputees, controlling robots with precision, aiding blind individuals through Braille displays, and enhancing virtual gaming experiences. The device, an electronic temporary tattoo designed to stimulate the skin through thermal, electrical, and mechanical means, consists of a silver electrode printed on tattoo paper, the device can be easily applied to human skin by wetting it with water. It employs an electro-thermo-pneumatic actuation strategy, generating tactile sensations through the expansion of air enclosed between thin films. Initial testing showed promising functionality, with further plans to develop displays with multiple tactile pixels for more complex sensations. Published in Advanced Electronic Materials, this research marks a significant advancement in ultra-thin electronics.

E-tattoo for the heart

Similarly, a novel flexible medical wearable could help patients manage heart disease. Led by researchers at The University of Texas at Austin, a team has developed an ultrathin, lightweight electronic tattoo, or e-tattoo, which adheres to the chest for continuous, mobile heart monitoring outside of clinical settings. Employing two sensors, the device offers a comprehensive assessment of heart health, enabling clinicians to detect potential issues early on. Professor Nanshu Lu, a lead author of the study, emphasized the importance of continuous monitoring for early diagnosis and prevention, suggesting that 80% of heart disease could be prevented with such technology.

Published in Advanced Electronic Materials, this study builds upon a previous chest e-tattoo project, presenting a wireless and mobile version enabled by small active circuits and sensors connected by stretchable interconnections. Unlike other monitoring systems, this e-tattoo is minimally intrusive and more comfortable for patients, weighing only 2.5 grams and running on a small battery with over 40 hours of life. It measures both the electrical signal from the heart (electrocardiogram, or ECG) and the acoustic signal from the heart valves (seismocardiogram, or SCG), offering a comprehensive understanding of cardiac function.

While ECG can be measured by mobile devices like smartwatches and SCG via a stethoscope, this device uniquely provides both measurements in a mobile solution. Lu emphasizes the significance of aligning these two measurements to assess cardiac time intervals, a key indicator of heart disease. Initial tests on healthy individuals have demonstrated promising results, with minimal errors compared to current monitoring methods. The next step is to test and validate the technology on various patient groups. This project is supported by the National Science Foundation’s Ascent program.

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