Design and fabrication of a microfluidic trap for full spectrum impedance scans of single bacteria.

The study and characterization of bacteria is nowdays drawing increasing interest among the scientific community. With the use of Impedance Flow Cytometry and Electrical Impedance Spectroscopy is possible to perform detailed analysis on shape, size and compositional properties of bacteria. In the present project, these techniques are intended to be employed in a biosensing device in combination with a customized microfluidic channel, designed with the ambition of trapping single bacteria by exploiting its own geometry. The trap mechanism is first developed and simulated by the means of the finite element method software COMSOL, highlighting the challenges associated with the single bacterium immobilization. The fabrication of the device components is performed in the cleanroom facility of DTU Nanolab, where, after undergoing several process optimizations, electrodes sets and a silicon mold for the creation of the microfluidic channel are successfully obtained, with the trap width having an average dimension of ∼ 650 nm. The biosensor is then assembled and tested in an experimental setup at DTU Bioengineering, to inspect the trapping capability and perform electrical impedance spectroscopy characterization. The former analysis is proven to produce some events, although the quality and repeatability of the results is challenged by the laboratory equipment, while the latter is prevented by difficulties associated to the alignment of the device components, which were overcomed only after the scheduled experimental period Although further testing and optimizations are necessary, the device implements promising functionalities and may represent a foundation for the development of an innovative biosensor.