Page 64 - TEXtalks. July- August 2023

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Flexible printed hybrid

electronics, growing market for

the textiles industry

One of the challenges in printing electronics onto textiles is the fabric’s rough texture – relative to some other
substrates such as paper or plastic. The surface morphology is dictated by the fibre structure and the fabric’s
form in addition to any stretch. The surface texture can require a thicker coating that brings implications for
comfort, flexibility, and cost.

The functional pigments that can be applied include electrically conductive, after-glow, magnetic, and
electroluminescence. Cold plasma spraying technology uses very small particles (<20mm) to enable low jet
temperatures. The advantage of this process is that no vacuum or wet chemical treatments are used. It also
offers a high deposition rate and freedom of design with precise and diffuse lines possible. Compositions can
also be layered to apply different functionalities and it is possible to coat ready-made clothing pieces with
conductive webs and foils allowing a good level of flexibility in connecting LEDs. Both coatings have achieved
positive results in kink resistance as well as torsion and bending as well and laundry tests.

There is a strong demand for stretch sensors, particularly in wearables, medical, health, and wellbeing, with
sensors commonly backed with polyurethane and placed directly onto the skin, and in other instances they are
placed on another material that acts as a substrate, including textiles.

Detecting exhaustion with

smart sportswear

Stretching produces distinctly measurable The yarn consists of inner fibre made of a conductive,
fluctuations in the yarn sensor’s charge. Researchers elastic rubber wrapped in a rigid wire and clad in a
at ETH Zurich have developed an electronic yarn thin layer of plastic. Stitching this yarn into the thigh
capable of precisely measuring how the body moves. section of a pair of stretchy running leggings means
Integrated directly into sportswear or work clothing, it that it will stretch and slacken at a certain rhythm as
can predict the wearer’s exhaustion level during the wearer runs. Each movement alters the gap
physical exertion. between the two fibres, and thus also the electric field
and the capacitor’s charge.
To test the new sensor, the researchers, led by Carlo
Menon, Professor of Mobile Health Technology,
integrated it into a pair of athletic leggings. Simply by To enable the textile sensor to send electrical signals
glancing at their smartphone, testers were able to see wirelessly to a smartphone, the researchers equipped
when they were reaching their limit and if they ought it with a loop antenna made of conducting yarn,
to take a break. which was also sewn directly onto the leggings.

July/August 2023