Long-Term Health Monitoring Possible through Breathable, Wearable Electronics on Our Skin


Nano Skin breathablewe
The diagram at top illustrates the structure of gold nanomesh conductors laminated onto the skin surface. The nanomesh, constructed from polyvinyl alcohol (PVA) nanofibers and a gold (Au) layer, adheres to the skin when sprayed with water, …more

A hypoallergenic electronic sensor can be worn on the skin continuously for a week without discomfort, and is so light and thin that users forget they even have it on, says a Japanese group of scientists. The elastic electrode constructed of breathable nanoscale meshes holds promise for the development of noninvasive e-skin devices that can monitor a person’s health continuously over a long period.

Wearable electronics that monitor heart rate and other vital health signals have made headway in recent years, with next-generation gadgets employing lightweight, highly elastic materials attached directly onto the skin for more sensitive, precise measurements. However, although the  and rubber sheets used in these devices adhere and conform well to the skin, their lack of breathability is deemed unsafe for long-term use: dermatological tests show the fine, stretchable materials prevent sweating and block airflow around the skin, causing irritation and inflammation, which ultimately could lead to lasting physiological and psychological effects.

“We learned that devices that can be worn for a week or longer for continuous monitoring were needed for practical use in medical and sports applications,” says Professor Takao Someya at the University of Tokyo’s Graduate School of Engineering whose research group had previously developed an on-skin patch that measured oxygen in blood.

In the current research, the group developed an electrode constructed from nanoscale meshes containing a water-soluble polymer, polyvinyl alcohol (PVA), and a gold layer—materials considered safe and biologically compatible with the body. The  can be applied by spraying a tiny amount of water, which dissolves the PVA nanofibers and allows it to stick easily to the skin—it conformed seamlessly to curvilinear surfaces of human skin, such as sweat pores and the ridges of an index finger’s fingerprint pattern.

Breathable, wearable electronics on skin for long-term health monitoring
An array of nanomesh conductors attached to a fingertip, top, and a scanning electron microscope (SEM) image of a nanomesh conductor on a skin replica, bottom. Credit: 2017 Someya Laboratory.

The researchers next conducted a skin patch test on 20 subjects and detected no inflammation on the participants’  after they had worn the device for a week. The group also evaluated the permeability, with water vapor, of the nanomesh conductor—along with those of other substrates like ultrathin plastic foil and a thin rubber sheet—and found that its porous mesh structure exhibited superior gas permeability compared to that of the other materials.

Furthermore, the scientists proved the device’s mechanical durability through repeated bending and stretching, exceeding 10,000 times, of a conductor attached on the forefinger; they also established its reliability as an electrode for electromyogram recordings when its readings of the electrical activity of muscles were comparable to those obtained through conventional gel electrodes.

Breathable, wearable electronics on skin for long-term health monitoring
The electric current from a flexible battery placed near the knuckle flows through the conductor and powers the LED just below the fingernail. Credit: 2017 Someya Laboratory.

“It will become possible to monitor patients’ vital signs without causing any stress or discomfort,” says Someya about the future implications of the team’s research. In addition to nursing care and medical applications, the new device promises to enable continuous, precise monitoring of athletes’ physiological signals and bodily motion without impeding their training or performance.

 Explore further: Novel e-skin may monitor health, vital signs

More information: Akihito Miyamoto et al, Inflammation-free, gas-permeable, lightweight, stretchable on-skin electronics with nanomeshes, Nature Nanotechnology (2017). DOI: 10.1038/nnano.2017.125

 

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SUBCOMMITTE EXAMINES BREAKTHROUGH NANOTECHNOLOGY OPPORTUNITIES FOR AMERICA

Chairman Terry: “Nanotech is a true science race between the nations, and we should be encouraging the transition from research breakthroughs to commercial development.”

WASHINGTON, DCThe Subcommittee on Commerce, Manufacturing, and Trade, chaired by Rep. Lee Terry (R-NE), today held a hearing on:

“Nanotechnology: Understanding How Small Solutions Drive Big Innovation.”

 

 

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“Great Things from Small Things!” … We Couldn’t Agree More!

 

Lateral crystal growth using oxide nanosheets as seed crystals


Oxide Crystals 201406041_press_release_fullIn the demonstration project for practical application at the Kanagawa Academy of Science and Technology (KAST), the research group led by Dr. Tetsuya Hasegawa (Professor, University of Tokyo; KAST principal researcher), Dr. Yasushi Hirose (Research Associate, University of Tokyo; KAST researcher) and Mr. Kenji Taira (postgraduate student, University of Tokyo; KAST research assistant), in collaboration with the team led by Dr. Takayoshi Sasaki (NIMS Fellow), developed a method for growing high-quality oxide thin films on a glass substrate which is an affordable material.

Solid phase crystallization (SPC) is a technique for crystallizing amorphous thin films of a target substance on a substrate by heat treatment and thereby obtaining thin film crystals consisting of large crystal grains, and it is known as a method for growing thin film crystals consisting of large crystal grains of a few to a few dozen micrometers. However, as this method is incapable of controlling the orientation of crystal grains on a substrate made of affordable materials, such as glass or plastic, it was impossible to fabricate thin films with adequate performance from highly anisotropic substances by this method.

Figure 1 (left) An atomic force microscope image of the titanium oxide thin film fabricated by the new method, showing that nanosheets, which provided seed crystals, exist at the center of crystal grains. (right) A map of crystal grain orientation determined by electron backscattering diffraction. The black lines correspond to the boundaries of individual crystal grains and the color represents their orientation. All crystal grains are highly (001) oriented.

The research group succeeded in growing thin film crystals consisting of highly oriented crystal grains, which were as large as a few micrometers or more, by coating a glass substrate with oxide sheets of about one nanometer in thickness, called oxide nanosheets, and using these nanocrystals as seed crystals in SPC.

The method employed in this research was an upgraded version of the nanosheet seed layer method published by NIMS in 2009. In the nanosheet seed layer method, a glass substrate is covered with oxide nanosheets, which are delaminated two-dimensional oxide crystals of about 1nm in thickness, and used just like a pseudo single-crystal substrate.

Although this method is superior in obtaining highly oriented thin film crystals, it has a disadvantage in that the size of the resulting crystal grains cannot be larger than the size of the oxide nanosheet (generally a few micrometers or smaller). By combining the nanosheet seed layer method with SPC, the research group at KAST succeeded in growing crystal grains in the lateral direction to a size of more than a few micrometers.

The titanium oxide transparent conductive films fabricated on the glass substrate by this new method exhibited low electrical resistance (3.6×10-4Ωcm) and mobility (13cm2V-1s-1), comparable to thin films grown on a single-crystal substrate.

The new method has been confirmed to also be applicable to strontium titanate, a typical substance used in electronics, and thus it is expected to promote the development of low-cost and high-performance devices using oxide thin film crystals.

Source: National Institute for Materials Science