Wearables research being conducted by imec and the Holst Centre in Eindhoven, Netherlands is focused on creating smart textiles. The possibilities of this research are exciting. As imec pointed out, "Textile[s] are the perfect platform for wearable electronics: you may forget to wear your smart watch, but you will never forget to wear your (sensor) T-shirt."
MD+DI spoke with Jeroen Van den Brand, program manager at the Holst Centre about the work on smart garments. He explained a few of the challenges that researchers are solving.
Read on for more about how smart clothing is made.
Advantage and challenge
Van den Brand pointed out that while his team works on wearable devices as well as smart clothing, garments do offer advantages in certain cases.
"The big advantage of a garment is that it covers a large part of your body which also means that sensing . . . measures over a large part of the human body. If you want to measure a really high-quality ECG signal . . . you have access to the full front and back of the body. You can just choose the optimal size and location of the electrodes while with a wristband that's just not possible," Van den Brand said.
He added, "If you want to monitor running, the way that people move their legs and the joints in their legs . . . you have to do that in clothing by integrating sensors into clothing."
Two of the main challenges in developing smart clothing is ensuring the electronics still work after repeated washing and that the clothing isn't bulky or inflexible as a result of being "smart."
Van den Brand explained, "The biggest challenge is washability . . . Clothing is known to degrade when you wash it multiple times. Electronics doesn’t have a degradation mechanism. It works or it doesn't work. To make the electronics so reliable that it survives the washing machine—that's the number one challenge."
He continued, "People accept electronics integrated into clothing, but they don’t accept that it's bulky. To really make it have the mechanical properties of clothing, that's clearly the second challenge."
These challenges are being addressed with system-in-foil technology, better known as "printed electronics." This technology is already being used in ECG monitoring devices worn as patches on the body, Van den Brand pointed out. "It is already used for medical devices, so that's a strong argument for also trying to use it here," he said.
In order to protect the electronics, "We laminate a very thin rubbery material on both sides of the electronics," Van den Brand said. "That doesn't influence the mechanical properties, but it does protect the electronics from moisture entering directly on the circuit."
This starts with a thin, rubbery material—with a thickness of 25-micrometers—as a base substrate.
The team works with materials from companies like DuPont, Van den Brand said. "[DuPont] develop[s] materials that inherently have better washability than normal printing materials."
The next step in the manufacturing process requires printing of circuitry patterns, Van den Brand said. This photo shows the base circuit patterns for an electronic circuit.
SiF for Other Components
According to imec, system-in-foil technology was used to make sensors, organic light emitting diodes, solar cells, and passive components.
Aside from printed electronics, rigid components need to be used too. Here, a chip is being assembled on a circuit.
"You start with plastic foils, print on that with conductive inks, and print sensors or actuators. A microcontroller is typically assembed on it," Van den Brand said.
According to imec, the team showed this integration technology could be used to combine foils with traditional components for LEDs, as an example.
This photo shows the flexibility of the foil that incorporates both printed and integrated electronics.
Stretchability is another requirement to make smart clothing wearable. According to imec, stretchability was accomplished by working with its associated lab at the University of Ghent, the Center for Microsystems Technology (CMST). Described as a technology "based on meandering structures between the electronic components," this allows electronics to stretch as much as 40% beyond their original length, imec said.
While many challenges have been met, imec notes that the washability of the material needs to be increased. Today, the material can be washed 10 times at about 120 degree Fahrenheit.
The team has shown that the base principle and the electronics work. Van den Brand said the next step is making printed sensors, such as electrodes that can take extremely sensitive measurements of ECG signals. The researchers also plan to integrate other types of sensors, like temperature sensors, into clothing.
While imec and the Holst Centre is focused on R&D, the technology platform is available to end users. According to Van den Brand, one of the end users is planning to launch a product based on this technology later this year.