A polyethylene glycol (PEG) microfluidic chip with nanostructures for bacteria rapid patterning and detection

This paper presents a new poly(ethylene glycol) (PEG) hydrogel based microchip with patterned nanoporous aluminum oxide membrane (AOM) for bacteria fast patterning and detection with low frequency impedance spectrum. The PEG hydrogel micropatterns on the saline-modified nanoporous alumina surface created controlled spatial distribution of hydrophobic and hydrophilic regions. For bacteria patterning and sensing purpose, 20 × 20 microwell arrays were fabricated. These microwell arrays were composed of hydrophilic PEG sidewalls and hydrophobic silane-modified AOM bottom. In the surrounded areas of the microwells where PEG was UV polymerized, solid hydrogel was covalently bonded with silane-modified membrane and this close covering prevented electrolyte flow through the portions underneath the membrane. Anti-E. coli antibody was added and washed to form the patterns in the microwells for bacteria capturing. Then, the target bacteria E. coli O157:H7 was successfully patterned and captured inside the microwells. For the control experiment, the non-target bacteria Staphylococcus was not observed on both PEG and AOM surfaces. The followed impedance experiments showed that this nanohole based electrochemical micro-system could detect this specific bacteria binding in the frequency domain less than 100 Hz with a low bacteria concentration of 102CFU/ml. The bacteria concentration effect on the impedance amplitude was also explored.