Researchers from the US, Japan, and South Korea have developed a new semiconductor material which breaks the mold by not utilizing covalent bonds between semiconducting materials. Why is such an invention important and how can this help with the future of wearable electronics?

Wearable Electronics

As electronics continue to shrink in size, they're also becoming cheaper and more widely available. Given this trend, engineers around the world are integrating circuits into just about everything they can. Electronics are taking over the automotive industry (raising all kinds of security questions in the process) and just about any household objects in the form of the growing IoT—and the number of IoT devices is projected to skyrocket over the next few years.

Despite this, developers are still wrestling with pushing wearable electronics into the mainstream of consumer consciousness. Successful examples of wearable products include fitness wearables and, to an extent, products like the Apple Watch. But a host of problems still plagues wearable device design, including the requirement of ultra-light and ultra-small components, a constraint which heavily impacts the computational power.

On top of that, wearable products commonly need to be flexible.

 

Borophene is a potential flexible material that could replace graphene. Image courtesy of Zhuhua Zhang/Rice University via Rice University

 

There are multiple potential flexible materials that could help wearables reach their next stage in design. Graphene is a contender for flexible OLED displays and borophene sheets have potential in developing devices that can withstand the flexibility requirements associated with human use.

However, there are some components which have remained inflexible, such as semiconductor devices. Semiconductors rely on strong covalent bonds to create crystalline structures (known for their inflexibility). Until now, flexible semiconductors were more theory than practice—but, thanks to a large team of researchers, this may not be the case anymore.

 

Enter Flexible Semiconductors

Researchers from the United States, Japan, and South Korea have teamed up to develop a new semiconductor device that is not only flexible but also has a potential for self-healing.

The semiconductor device is very similar in layout to a typical MOSFET device found in silicon-based designs—but with a twist! All layers and materials are made with flexible materials which allow for the whole device to flex, twist, and turn with little impact on performance. The source and drain connections are made with CNT.PEDOT:PSS, which are a mixture of carbon nanotubes and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate.

 

The flexible semiconductor. Image credit: (c) Nature (2016). DOI: 10.1038/nature20102 via Phys.org

 

The semiconductor material, itself, is made of DPP-Polymer which is a p-type material using diketopyrrolo-pyrrole-dithiophene-thienothiophene. The dielectric between the gate and semiconductor material is PDMS which is a silicone-based flexible compound.

The gate layer is made using a carbon nanotube material with the whole device sitting on top of a flexible rubber substrate. The flexible device can maintain its electrical properties even after 500 stretching cycles and can be repaired by heating to 150ºC using a steam chamber for 30 minutes.

However, according to the researchers, the semiconductor device presently requires too high voltage for portable and wearable applications. This means that heat management will likely be a key focus for the researchers going forward.

 

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The Future of Flexible Devices

As electronics become integrated into everyday products, it's clear that wearable and flexible electronics are a part of the future of electronics. With a population that is becoming increasingly dependent on electronics and computing power, many anticipate a future in which people will want devices embedded into body parts such as the eye and skin for easy access to email and social media platforms.

The initial goal for the flexible semiconductor was to create an electrical device that can behave like organic tissue, able to be moved around without affecting its properties. This newest research demonstrates this capability and gives credence to the idea that flexible semiconductors are a likely part of future electronics design.

 

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