In Situ Fabrication of Nanoporous Alumina into a Microwell Array

Abstract: Existing method for the antibiotic susceptibility test (AST) requires 2-3 days to produce the result. For patients with urinary tract infection (UTI), this lengthy process is critical because they must bear the pain during this period. A newly proposed idea to shorten the time is by using phenotypic antibiotic susceptibility test (AST) method on single bacteria.The first step to achieve the goal is to design and fabricate a platform to capture single bacteria and remove unwanted particles. An integrated micro and nanomembrane structure fulfill the requirement. The micro membrane structure is used to capture intended particles and block larger particles, while nanomembrane is used to remove unwanted nanoparticles. Micro-membrane structure is designed as an array of the microwell, and each microwell is expected to capture the bacteria. The thickness of microwell must be comparable to the bacteria dimension to make the observation of single bacteria be possible. Otherwise, there will be a stack of bacteria and only the bacteria at the top can be observed.The nanoporous membrane is created using aluminum foil through the anodization process and microwell structure is created using OSTE polymer through photolithography. Both materials are inexpensive and the fabrication process is fairly simple. In the final result, the nanoporous membrane is successfully integrated with microwell array. Each microwell has diameter 200 µm and thickness 100 µm. The nanoporous membrane has pore diameters 70nm, thickness 200nm, and approximate porosity 24.6%.This project successfully produces a complete device by integrating microwell array, nanoporous membrane, and a device substrate. However, the desired thickness for the microwell array is not achieved. The thickness of the microwell is 100 µm while the size of a bacteria is only a few microns. Thin microwell array with 5 µm thickness is easily detached from the substrate during development. To solve this problem, a different mixture of developer solution is needed that will develop the OSTE but will not destroy the structure. Nevertheless, this early design of the platform is a promising start in the early development of rapid antibiotic susceptibility test (AST).