November 15, 2011

Carbon Nanotube Active-Matrix Backplanes for Conformal Electronics and Sensors

NanoLetters - Carbon Nanotube Active-Matrix Backplanes for Conformal Electronics and Sensors (12 pages)

In this paper, we report a promising approach for fabricating large-scale flexible and stretchable electronics using a semiconductor-enriched carbon nanotube solution. Uniform semiconducting nanotube networks with superb electrical properties (mobility of ∼20 cm2 V^-1 s^-1 and ION/IOFF of ∼10^4) are obtained on polyimide substrates. The substrate is made stretchable by laser cutting a honeycomb mesh structure, which combined with nanotubenetwork transistors enables highly robust conformal electronic devices with minimal device-to-device stochastic variations. The utility of this device concept is demonstrated by fabricating an active-matrix backplane (12 X 8 pixels, physical size of 6 X 4 cm2) for pressure mapping using a pressure sensitive rubber as the sensor element

In the future, pixel density can be further improved by decreasing the size of both the SWNT active region and the contact region to PSR. This solution-based approach can be potentially combined with inkjet printing of metal contacts to achieve lithography-free fabrication of low-cost flexible and stretchable electronics with superb electrical and mechanical properties. Notably, to achieve stretchability using robust PI substrates, a concept often used in the paper decoration industry was applied by proper laser cutting of the substrate. The back-plane technology explored here can be further expanded in the future by adding various sensor and/or other active device components to enable multifunctional artificial skin

Semiconductor-enriched SWNT TFTs on flexible substrates. (a) Schematic of a mechanically flexible/stretchable active-matrix back-plane (6X4 cm2 with 12X8 pixel array) based on SWNT TFTs, and an expanded schematic of a single TFT. (b) Atomic force microscopy images of SWNT networks on a PI substrate, showing that the density can be controlled by the nanotube deposition time (5, 30, and 90 min; top to bottom, respectively). Average length of nanotubes is ∼0.8 μm.

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