Tag Archives: wearable bioelectronics

Printing wearable circuits onto skin

It seems that this new technique for creating wearable electronics will be more like getting a permanent tattoo where the circuits are applied directly to your skin as opposed to being like a temporary tattoo where the circuits are printed onto a substrate and then applied to then, worn on your skin.

Caption: On-body sensors, such as electrodes and temperature sensors, were directly printed and sintered on the skin surface. Credit: Adapted from ACS Applied Materials & Interfaces 2020, DOI: 10.1021/acsami.0c11479

An Oct. 14, 2020 American Chemical Society (ACS) news release (also on EurekAlert) announced this latest development in wearable electronics,

Wearable electronics are getting smaller, more comfortable and increasingly capable of interfacing with the human body. To achieve a truly seamless integration, electronics could someday be printed directly on people’s skin. As a step toward this goal, researchers reporting in ACS Applied Materials & Interfaces have safely placed wearable circuits directly onto the surface of human skin to monitor health indicators, such as temperature, blood oxygen, heart rate and blood pressure.

The latest generation of wearable electronics for health monitoring combines soft on-body sensors with flexible printed circuit boards (FPCBs) for signal readout and wireless transmission to health care workers. However, before the sensor is attached to the body, it must be printed or lithographed onto a carrier material, which can involve sophisticated fabrication approaches. To simplify the process and improve the performance of the devices, Peng He, Weiwei Zhao, Huanyu Cheng and colleagues wanted to develop a room-temperature method to sinter metal nanoparticles onto paper or fabric for FPCBs and directly onto human skin for on-body sensors. Sintering — the process of fusing metal or other particles together — usually requires heat, which wouldn’t be suitable for attaching circuits directly to skin.

The researchers designed an electronic health monitoring system that consisted of sensor circuits printed directly on the back of a human hand, as well as a paper-based FPCB attached to the inside of a shirt sleeve. To make the FPCB part of the system, the researchers coated a piece of paper with a novel sintering aid and used an inkjet printer with silver nanoparticle ink to print circuits onto the coating. As solvent evaporated from the ink, the silver nanoparticles sintered at room temperature to form circuits. A commercially available chip was added to wirelessly transmit the data, and the resulting FPCB was attached to a volunteer’s sleeve. The team used the same process to sinter circuits on the volunteer’s hand, except printing was done with a polymer stamp. As a proof of concept, the researchers made a full electronic health monitoring system that sensed temperature, humidity, blood oxygen, heart rate, blood pressure and electrophysiological signals and analyzed its performance. The signals obtained by these sensors were comparable to or better than those measured by conventional commercial devices. 

Here’s a link to and a citation for the paper,

Wearable Circuits Sintered at Room Temperature Directly on the Skin Surface for Health Monitoring by Ling Zhang, Hongjun Ji, Houbing Huang, Ning Yi, Xiaoming Shi, Senpei Xie, Yaoyin Li, Ziheng Ye, Pengdong Feng, Tiesong Lin, Xiangli Liu, Xuesong Leng, Mingyu Li, Jiaheng Zhang, Xing Ma, Peng He, Weiwei Zhao, and Huanyu Cheng. ACS Appl. Mater. Interfaces 2020, 12, 40, 45504–45515 Publication Date:September 11, 2020 DOI: https://doi.org/10.1021/acsami.0c11479 Copyright © 2020 American Chemical Society

This paper is behind a paywall.

You mean Fitbit makes mistakes? More accuracy with ‘drawn-on-skin’ electronics

A July 30, 2020 news item on ScienceDaily announces news about more accurate health monitoring with electronics applied directly to your skin,

A team of researchers led by Cunjiang Yu, Bill D. Cook Associate Professor of Mechanical Engineering at the University of Houston, has developed a new form of electronics known as “drawn-on-skin electronics,” allowing multifunctional sensors and circuits to be drawn on the skin with an ink pen.

The advance, the researchers report in Nature Communications, allows for the collection of more precise, motion artifact-free health data, solving the long-standing problem of collecting precise biological data through a wearable device when the subject is in motion.

The imprecision may not be important when your FitBit registers 4,000 steps instead of 4,200, but sensors designed to check heart function, temperature and other physical signals must be accurate if they are to be used for diagnostics and treatment.

A July 30, 2020 University of Houston news release (also on EurekAlert) by Jeannie Kever, which originated the news item, goes on to explain why you might want to have electronics ‘drawn on your skin’,

The drawn-on-skin electronics are able to seamlessly collect data, regardless of the wearer’s movements.  

They also offer other advantages, including simple fabrication techniques that don’t require dedicated equipment.

“It is applied like you would use a pen to write on a piece of paper,” said Yu. “We prepare several electronic materials and then use pens to dispense them. Coming out, it is liquid. But like ink on paper, it dries very quickly.”

Wearable bioelectronics – in the form of soft, flexible patches attached to the skin – have become an important way to monitor, prevent and treat illness and injury by tracking physiological information from the wearer. But even the most flexible wearables are limited by motion artifacts, or the difficulty that arises in collecting data when the sensor doesn’t move precisely with the skin.

The drawn-on-skin electronics can be customized to collect different types of information, and Yu said it is expected to be especially useful in situations where it’s not possible to access sophisticated equipment, including on a battleground.

The electronics are able to track muscle signals, heart rate, temperature and skin hydration, among other physical data, he said. The researchers also reported that the drawn-on-skin electronics have demonstrated the ability to accelerate healing of wounds.

In addition to Yu, researchers involved in the project include Faheem Ershad, Anish Thukral, Phillip Comeaux, Yuntao Lu, Hyunseok Shim, Kyoseung Sim, Nam-In Kim, Zhoulyu Rao, Ross Guevara, Luis Contreras, Fengjiao Pan, Yongcao Zhang, Ying-Shi Guan, Pinyi Yang, Xu Wang and Peng Wang, all from the University of Houston, and Jiping Yue and Xiaoyang Wu from the University of Chicago.

The drawn-on-skin electronics are actually comprised of three inks, serving as a conductor, semiconductor and dielectric.

“Electronic inks, including conductors, semiconductors, and dielectrics, are drawn on-demand in a freeform manner to develop devices, such as transistors, strain sensors, temperature sensors, heaters, skin hydration sensors, and electrophysiological sensors,” the researchers wrote.

This research is supported by the Office of Naval Research and National Institutes of Health.

Caption: A new form of electronics known as “drawn-on-skin electronics” allows multifunctional sensors and circuits to be drawn on the skin with an ink pen. Credit: University of Houston

Here’s a link to and a citation for the paper,

Ultra-conformal drawn-on-skin electronics for multifunctional motion artifact-free sensing and point-of-care treatment by Faheem Ershad, Anish Thukral, Jiping Yue, Phillip Comeaux, Yuntao Lu, Hyunseok Shim, Kyoseung Sim, Nam-In Kim, Zhoulyu Rao, Ross Guevara, Luis Contreras, Fengjiao Pan, Yongcao Zhang, Ying-Shi Guan, Pinyi Yang, Xu Wang, Peng Wang, Xiaoyang Wu & Cunjiang Yu. Nature Communications volume 11, Article number: 3823 (2020) DOI: https://doi.org/10.1038/s41467-020-17619-1

This paper is open access.