Stainless microfluidic probe with 2D-array microapertures

A microfluidic probe (MFP) does not require physical walls for flow channels, enabling application of a chemical solution in an open space by injecting and aspirating the solution. However, in conventional MFP fabrication methods, the use of a 2D aperture array at narrow intervals to enhance the function of treatment remains limited. In this study, we developed a stainless MFP (stMFP) to produce a 2D aperture array at narrow intervals. The stMFP was developed using a stacking technique in which stainless steel substrates fabricated by photolithography and a wet etching process were stacked and bonded through thermal diffusion. This process resulted in a 6-row and 8-column aperture array with an aperture size of 100 × 150 µm and a narrow interval of 50 µm. The surface treatment area was evaluated by biopatterning of a fluorescent antibody. The results showed that the stMFP biopatterned a minimum treatment area of 3.3 × 103 µm2, which could be controlled between 5.1 × 104 µm2 and 3.0 × 105 µm2 by changing the aperture arrangement. In addition, when two types of fluorescent antibodies were alternately injected in the row direction, six independent treatment areas of 6.1 × 104 µm2 were formed over a wide area of 3.8 × 105 µm2. Furthermore, biopatterning using a 4 × 4 aperture array showed that a 2D treatment area with 4-rows and 2-columns can be produced with an area of 4.5 × 105 µm2. A single stMFP can form various 2D treatment patterns, which is expected to realize high-performance bioprocessing in the field of biology.