Stretchable Semiconductors Break New Ground
In a significant development towards creating fully elastic electronic systems, a research team led by Penn State has discovered a method to enhance the stretchability of a type of semiconductor known to be brittle.
These elastic electronic systems are crucial for a range of applications, including advanced human-machine interfaces, smart health care, and artificial skins.
Overcoming the Barrier of Brittle Semiconductors
Principal investigator Cunjiang Yu, Dorothy Quiggle Career Development Associate Professor of Engineering Science and Mechanics and of Biomedical Engineering at Penn State, explained that all components of an elastic electronic system must be flexible and stretchable.
While this has been achieved for most components, one type of semiconductor remained brittle.
Yu’s team developed a solution to compensate for this shortcoming, bringing the field closer to realizing completely flexible systems. Their work has been published in Nature Electronics.
A Balancing Act between P-Type and N-Type Semiconductors
Elastic electronic technology requires stretchy elastic semiconductors, mainly of the p-type, which conducts electricity primarily through positive charges.
However, n-type semiconductors, which conduct electricity through negative charges, are equally necessary for creating devices such as complementary integrated electronics, optoelectronics, p-n junction devices, and more.
These semiconductors are typically rigid, and strategies to make them more mechanically stretchable are essential for creating completely stretchable transistors and circuits.
Sandwich Solution
To improve the stretchability of n-type semiconductors, researchers sandwiched the semiconductor between two elastic materials, or elastomers.
These polymers can stretch and revert to their original shape.
This approach significantly enhanced the stretchability of the semiconductor and suppressed the formation of microcracks, which are tiny defects that can deteriorate electrical performance and result in mechanical failure.
Stretchable Transistors Tested Successfully
After undergoing a series of stress and stability tests, the sandwiched semiconductor displayed impressive performance, maintaining high performance even when stretched 50% in either direction.
It also demonstrated long-term stable operation for over 100 days in an ambient environment, a crucial factor given n-type semiconductors can lose efficiency when exposed to oxygen and moisture.
The team will continue to optimize the layer configuration to reduce microcrack density and improve the performances of the stacked materials.
Toward Fully Stretchable Electronics
With the successful development of a stretchable n-type semiconductor, the team is closer to achieving fully stretchable, rubbery integrated circuits, a significant step forward in the field of elastic electronics.
The study was published in Nature Electronics.
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