Researchers tailor power source for wearable electronics

December 16, 2015
Radially aligned titanium oxide nanotubes increase surface area, to pack more power in the confines of clothing. Credit: Courtesy of the journal Energy Storage Materials

Wearable power sources for wearable electronics are limited by the size of garments.

With that in mind, researchers at Case Western Reserve University have developed flexible wire-shaped microsupercapacitors that can be woven into a jacket, shirt or dress.

By their design or by connecting the capacitors in series or parallel, the devices can be tailored to match the charge storage and delivery needs of electronics donned.

While there's been progress in development of those electronics—body cameras, smart glasses, sensors that monitor health, activity trackers and more—one challenge remaining is providing less obtrusive and cumbersome power sources.

"The area of clothing is fixed, so to generate the power density needed in a small area, we grew radially-aligned titanium oxide nanotubes on a titanium wire used as the main electrode," said Liming Dai, the Kent Hale Smith Professor of Macromolecular Science and Engineering. "By increasing the surface area of the electrode, you increase the capacitance."

Dai and Tao Chen, a postdoctoral fellow in molecular science and engineering at Case Western Reserve, published their research on the microsupercapacitor in the journal Energy Storage Materials this week. The study builds on earlier carbon-based supercapacitors.

A capacitor is cousin to the battery, but offers the advantage of charging and releasing energy much faster.

How it works

In this new supercapacitor, the modified titanium wire is coated with a solid electrolyte made of polyvinyl alcohol and phosphoric acid. The wire is then wrapped with either yarn or a sheet made of aligned carbon nanotubes, which serves as the second electrode. The titanium oxide nanotubes, which are semiconducting, separate the two active portions of the electrodes, preventing a short circuit.

In testing, capacitance—the capability to store charge—increased from 0.57 to 0.9 to 1.04 milliFarads per micrometer as the strands of yarn were increased from 1 to 2 to 3.

When wrapped with a sheet of carbon nanotubes, which increases the effective area of electrode, the microsupercapactitor stored 1.84 milliFarads per micrometer. Energy density was 0.16 x 10-3 milliwatt-hours per cubic centimeter and .01 milliwatt per cubic centimeter.

Whether wrapped with yarn or a sheet, the microsupercapacitor retained at least 80 percent of its capacitance after 1,000 charge-discharge cycles. To match various specific power needs of wearable devices, the wire-shaped capacitors can be connected in series or parallel to raise voltage or current, the researchers say.

When bent up to 180 degrees hundreds of times, the capacitors showed no loss of performance. Those wrapped in sheets showed more mechanical strength.

"They're very flexible, so they can be integrated into fabric or textile materials," Dai said. "They can be a wearable, flexible power source for and also for self-powered biosensors or other biomedical devices, particularly for applications inside the body."

Dai 's lab is in the process of weaving the wire-like capacitors into fabric and integrating them with a wearable device.

Explore further: New nanomaterial maintains conductivity in 3-D

More information: Tao Chen et al. Flexible and wearable wire-shaped microsupercapacitors based on highly aligned titania and carbon nanotubes, Energy Storage Materials (2016). DOI: 10.1016/j.ensm.2015.11.004

Related Stories

New nanomaterial maintains conductivity in 3-D

September 4, 2015

An international team of scientists has developed what may be the first one-step process for making seamless carbon-based nanomaterials that possess superior thermal, electrical and mechanical properties in three dimensions.

Smart supercapacitor fiber with shape memory

November 20, 2015

Wearing your mobile phone display on your jacket sleeve or an EKG probe in your sports kit are not off in some distant imagined future. Wearable "electronic textiles" are on the way. In the journal Angewandte Chemie, Chinese ...

Recommended for you

Particles self-assemble into Archimedean tilings

December 8, 2016

(Phys.org)—For the first time, researchers have simulated particles that can spontaneously self-assemble into networks that form geometrical arrangements called Archimedean tilings. The key to realizing these structures ...

Nano-calligraphy on graphene

December 8, 2016

Scientists at The University of Manchester and Karlsruhe Institute of Technology have demonstrated a method to chemically modify small regions of graphene with high precision, leading to extreme miniaturisation of chemical ...

2 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

betterexists
1 / 5 (1) Dec 16, 2015
Just Follow this Procedure:
Visit Walmart.
Present at the Counter which garment you want.
It should ship that to your home the same day with the Wearable Electronics integrated!
As simple as that! You just pay additional costs until it becomes the norm.
Walmart should have a Central office where copies of all garments are held in storage.
vidyunmaya
not rated yet Dec 26, 2015
Titanium dioxide in trigger mode charge transfer has given excellent results long time back in my research and contemplated wearable mode- but could not continue.
The methods shown here have wide potential applications and flexibility. my sincere best wishes to the team.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.