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Posted on January 9, 2017 by

A flexible transistor that conforms to skin

Researchers have created a stretchy transistor that can be elongated to twice its length with only minimal changes in its conductivity. The development is a valuable advancement for the field of wearable electronics. To date, it has been difficult to design a transistor using inherently stretchable materials that maintains its conductivity upon being stretched.
Here and Jie Xu devise a clever and scalable way to confine organic conductors inside a rubbery polymer to create stretchy transistors. They took a semiconducting polymer, called DPPT-TT, and confined it inside another polymer, SEBS, which has elastic properties.
As the two polymers don't like to mix with each other, the DPPT-TT forms thin bundles within the SEBS matrix. Testing and analysis of this new combination reveal that it works as an effective transistor, even as it is repeatedly stretched up to 100% of its length. While the material demonstrated a normal conductivity of 0.59 cm2/Vs on average, this dropped only slightly to 0.55 cm2/Vs when being stretched to twice its length.
The authors did not observe any visible cracks in the film after 100 cycles of being stretched. Fabricated transistors made of the film with carbon nanotubes as the electrodes formed a flexible material that could be attached to human skin, for example, retaining its conductive properties when heavily stretched along the surface of a finger as it bends. This advancement is highlighted in a Perspective by Simone Napolitano.
Source and top image: American Association for the Advancement of Science
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