Patterning a nanowell sensor biochip for specific and rapid detection of bacteria

This paper presents the fabrication process of a SEPTIC (SEnsing of Phage-Triggered Ion Cascades) chip, consisting of two Ti contact pads and a 150 nm wide Ti nanowell device on LiNbO3 substrate. The patterning was fulfilled by combining electron beam lithography, contact photolithography and reactive ion etching. When connected to an external preamplifier and spectrum analyzer, the nanowell can probe nano-scale electric field fluctuations. The use of this chip as nano-scale electric field probe was demonstrated by detecting the transitory ion efflux from bacteria being infected by phage. Our experiment showed that the electric field noise follows 1/f2 power spectrum when the bacteria are sensitive to the phage, whereas 1/f noise corresponds to bacteria resistant to the phage. The use of fluctuation-enhanced sensing can provide sensitivity orders of magnitude higher than conventional sensing that detects changes only in the mean value of electrical signals.