This technology has many applications in the printing industry, specifically in the printing of microelectronics on flexible substrates, including displays, circuits, photovoltaic (PV) arrays, and radio frequency identification (RFID) tags. In general, micro-contact printing can be used to transfer-print a wide range of materials (e.g. quantum dots, carbon nanotubes and graphene, functional polymers, living cells, metal nanoparticles, and colloid crystals) onto flat and curved substrates.
The micro-contact printing technique has shown the ability to directly print feature sizes as small as 500 nm. This high-resolution printing is often achieved using a micro-structured polydimentylsiloxane (PDMS) stamp. However, PDMS displays a low elastic modulus which can cause structural failing and limit the reliability of the printing process. Therefore, micro-contact printing has yet to be successfully implemented in high-throughput production of microelectronic devices, while maintaining high resolution.
To address this problem, the inventors have developed a new class of stamp material composed of vertically aligned multi-walled carbon nanotubes (CNTs) conformally coated with functional polymers. A thermal chemical vapor deposition (CVD) process is used to grow patterned CNT arrays on silicon substrates, forming vertically aligned “forests” or “arrays” where the individual CNTs are perpendicular to the substrate. The top layer of the CNTs is removed by plasma treatment, which reduces the surface modulus and enables conformal contact against the target substrates. The individual CNTs within the arrays are coated with functional polymer films, such as poly-perfluorodecylacrylate, p(PFDA), by initiated chemical vapor deposition (iCVD) process. This conformal p(PFDA) coating is an average thickness of 30 nm and ensures the microstructures do not shrink or collapse after wetting and dewetting. Finally, the polymer coated CNT arrays are plasma-treated again to control the surface wettability. By simple procedure of transfer printing using the new CNT stamp, micro patterns of diverse “ink” materials can be printed on various substrates with either flat or curved surface.
Direct-printing allows for low-cost, rapid
and mass production capabilities
CNT stamp can be sized to sub-micrometer
scale while retaining mechanical robustness
Engineered for automated, mass production
systems for high-throughput production
Far-ranging applications including:
repeatable liquid printing, electrical micro-contact printing, and tunable
wettability/adhesion of stamp surface depending on coating