Rapid fabrication of sieved microwells and cross-flow microparticle trapping

Abstract

The use of microwells is popular for a wide range of applications due to its’ simplicity. However, the seeding of conventional microwells, which are closed at the bottom, is restricted to gravitational sedimentation for cell or particle deposition and therefore require lengthy settling times to maximize well occupancy. The addition of microfluidics to the capture process has accelerated cell or particle dispersion and improved capture ability but is mostly limited to gravitationally-driven settling for capture into the wells. An alternative approach to conventional closed-microwells, sieved microwells supersedes reliance on gravity by using hydrodynamic forces through the open pores at the bottom of the microwells to draw targets into the wells. We have developed a rapid fabrication method, based on flow lithography techniques, which allows us to easily customize the mesh pore sizes in a simple two-step process. Finally, by combining this microwell design with cross-flow trapping in a microfluidic two-layered channel, we achieve an 88 ± 6% well occupancy in under 10 s.

A New Rapid Microfluidic Detection Platform Utilizing Hydrogel‐Membrane under Cross‐Flow

“…Microfluidic Channel Fabrication: Molds for the double layered microfluidic channels were fabricated using soft lithography as described previously. [26] Channels designed in AutoCAD (Autodesk) were printed at ≈1 pixel per micrometer resolution (25 000 dpi) by CAD/Art Services (OR, USA). SU-8 2025 or 2050 photoresist was spin-coated onto a 100 mm diameter silicon wafer then exposed to unfiltered UV light through a custom photomask with an NxQ 4006 mask aligner (Neutronix Quintel).…”

“…We fabricate hydrogel membranes using slit flow photo lithography [23,26] in a PDMS channel of 50 µm height. Briefly: channels are first filled with a poly(ethylene glycol) diacrylate (PEGDA), acrylic acid and photoinitiator (Darocur 1173) pre polymer solution, wherein hydrogels are polymerized by expo sure to UV light through a photomask and a 10× objective lens.…”

“…The installation of membranes into prefab ricated doubledlayered PDMS channels was previously devel oped by our group. [23,26] The important design consideration for this installation is the physical parameters of the mem brane and the geometrical configurations of the installation site shown in Figure 1c. For instance, the length of the mem brane should be identical to the length of the site and the thick ness of membrane should be shorter than the site thickness to secure the membrane during crossflow operation (Figure 1c).…”

“…By increasing the flow rate of the B4F solution twofold from 150 to 300 µL min −1 , the time required for the membrane satu ration decreases from ≈15 to ≈10 min (Figure 2). By increasing the duration of sample flow, greater fluorescent signals were produced, while also resulting in a reduced rate of signal gain, [23,26] for carboxylated PEG membranes that are later functionalized with avidin. A pre-polymer solution composed of acrylic acid, PEGDA700, and Darocur 1173 is introduced into a PDMS microfluidic channel wherein it is exposed to a fixed square-pattern of UV light (in dashed lined and yellow).…”

Latest Updates on the Advancement of Polymer-Based Biomicroelectromechanical Systems for Animal Cell Studies

“…This device opened new channels to improve capture ability and well occupancy, showing great promise for single-cell analysis. Moreover, its versatile fabrication methods allowed the device to be adaptable into a wide range of sizes and shapes [41]. Scientists use various geometric designs to isolate cells in devices.…”