AT Case Western Reserve University, researchers have developed an affordable way to turn an ordinary shirt into an electronic smart shirt. This helps track and adjust body temperature or even allow the wearer to apply heat to an aching back or shoulder.
All developed from a design printed on the fabric of the shirt or any other garment.
The key to their innovation: a highly conductive ink and a simple screen-printing process that leads to a waterproof, breathable and extremely flexible design that could function as a heating element while being powered by a coin-sized battery .
According to market analysts, the market for wearable technologies, such as the Apple Watch, FitBit and Bluetooth headphones, is booming. However, a growing segment is made up of electronic technology fixed in clothing, implanted in the body of the user, even tattooed on the skin.
The Case Western Reserve-led group of scientists believe their technique stands out in the expanding wearable technology market for its ease, durability, comfort – and ultimately, one day, its price.
They say their process, which passed in lab tests, could one day be used in mass production. The research group included collaborators from Wuhan, China. The research was published in the journal Small.
We believe this is a much better method than other attempts to create truly wearable technology because it not only performs well initially, but is also durable in the long run..
Changyong (Chase) Cao, Study Lead Author and Assistant Professor, Mechanical and Aerospace Engineering, Case Western Reserve University
Cao is an assistant professor at the Case School of Engineering. He is also director of the Soft Machinery and Electronics Laboratory at Case Western Reserve. Cao said most of the designs available for integrating electronics into clothing have an elastomer or polymer surface. Often these types of surfaces are uncomfortable and non-breathable.
The difference: a conductive and durable ink
Cao said scientists have tried two other methods to combine electronic fibers into the fabric: spinning them into the material or depositing conductive materials on the surface of the fabric. The latter, like spray coating and dip coating, is more common because it is faster and more economical.
Our new method improves on these by using the low cost screen printing method to achieve a higher level of resolution. This allows us to print the ink in more aesthetic patterns or intricate designs. Printed e-textiles are very stretchy and can continue to perform well even after multiple washes.
Changyong (Chase) Cao, Study Leader and Assistant Professor, Mechanical and Aerospace Engineering, Case Western Reserve University
According to the scientists, the vital factor was the use of silver fractal dendrites – microscopic branch-like silver filaments. The filaments conduct electricity well, even if they are handled or deformed during use.
The researchers added the microscopic solid metals to a water-based ink, binding it to the ink molecules with a clear, highly elastic adhesive.
The ink, previously covered with a thin layer of an invisible waterproofing agent which prevents cracking of the electrodes, can be printed or sprayed onto the fabric.
Additionally, the ink works as a conductor of small amounts of electricity and can sense body movement and perform personalized temperature management or control.
The scientists used a small button cell, or button cell, like those found in car keychains, thermometers or wristwatches to power the ink-based heating unit.
Tian, B., et al. (2022) Fully printed stretch and multifunctional electronic textiles for aesthetic wearable electronic systems. Small. doi.org/10.1002/smll.202107298.