Transfer-Print of CNTs and its Application to Cell Scaffold

A bio-chip using cultured cells is developed for an application to drug screening. Carbon nanotubes (CNTs) are a candidate for this electrode material. A transfer-prints is expected to be a CNT-patterning technique applicable to soft material. This present paper is intended to show some basic properties about the transfer-print of CNTs, and also to demonstrate the possibility of the CNTs as a cell scaffold. The present study prepared several types of surface-modified Si substrate with different wettability to investigate the effects of wettability on the transferring ratio of CNTs. Some Si substrates are terminated by OH or H groups, while other substrates are coated with hydrophobic or hydrophilic self-assembled monolayers. The stamps for transfer-print, which have circular dots (50-μm diameter) or a straight ridge (50-μm width) array, are fabricated using poly-dimethyl-siloxane (PDMS). The surfaces of PDMS stamps are inked by single-walled CNTs by a pre-transferring or casting process. The transfer-prints to surface-modified Si surfaces allow the CNTs to be formed in lines of several tens of micrometers, while the coverage of transfer-printed CNTs is also dominated by surface wettability. The coverage of transfer-printed CNTs increases with the water contact angle of the Si surface. It is reasonable that the transfer-print of CNTs is performed by hydrophobic interactions. Meanwhile, two kinds of polymer (polystyrene (PS) and polyethylene terephthalate (PET)) sheets are also utilized as a substrate. The transfer-prints with heating around the softening point of the polymer allow CNTs to be accurately patterned into an array of 50-μm dots. The coverage of CNTs is 94% on the PET substrate. The PS sheet with patterned CNTs is applied to a cell scaffold. PC12 cells are cultured on the PS sheets so that the cells are selectively adhered to the transfer-printed CNTs. The adhered cells are extended with some pseudopods. It is demonstrated that the transfer-printed CNTs are expected to be electrodes of the cell scaffold.