Biocompatible photoresists as nonchemically amplified resist systems and their biomolecular patterning applications

Abstract

The photoresists are being extensively used for a wide variety of applications including the microelectronic device fabrication as an advanced technique and the bio-microdevices fabrication as a new pioneer field. The biotechnology and biomedical studies especially related to bio-microdevices such as a biochip, biosensor, and biopattern have been important to satisfy the eco-friendly and nontoxic requirements. Therefore we designed and synthesized the biocompatible, aqueous processible, and nontoxic photoresists able to be utilized to bioresist field. Our designed polymers were composed of different monomer ratios of photosensitive and bioapplicable DOBEMA, biocompatible and hydorphilic PEGMA, and MMA. Water solubility of these poly(DOBEMA-co-PEGMA-co-MMA)s is controlled by changing the mole fraction of PEGMA and switched to their dissolving properties by a photochemical reaction of photosensitive DOBEMA. Upon UV light irradiation, the diazoketo-functionalized groups in the polymer are dicomposed, released to nontoxic nitrogen molecules as byproduct, and then changed to carboxylic groups due to undergoing Wolff rearrangement. As the DUV-irradiated polymers comprising hydrophilic PEGMA became more hydrophilc by carboxylic acid groups created through Wolff rearrangement, these were well dissolved in base solution. However, in deionized water, they were insoluble despite the higher hydrophilicity, but swollen. This insolubility indicates that the hydrogen bonding forces between the carboxylic acids and the ethylene glycol segments in and on the polymer chains are not dissociatted in deionized water. The energy of this attraction is as high as the same to the weakest among all the covalent bonds, and occurs with multiple interactions between polymers or within a polymer. Therefore when used with deionized water as developer, the poly(DOBEMA-co-PEGMA-co-MMA) is obtained with negative pattern which remained in the irradiated region because of hydrogen bonds between t...