Polymers have a great potential to be used for BioMEMS applications because many polymers are low cost, can be processed easily, and possess a broad range of physical and chemical properties. By combining various bulk or surface machining techniques and conventional manufacturing methods such as silicone rubber casting, injection molding, hot embossing, and reaction injection molding, polymer platforms containing complex flow patterns at the microscale can be fabricated. However, packaging (bonding, surface modification, and reagent loading) of microscale feature is still a challenging issue in the design and fabrication of polymer-based microfluidic devices.
A resin-gas injection technique for bonding and surface modification of polymer-based microfluidic platforms was developed. M icrofluidic platform and the lid were firstly encapsulated in the holder; several drops of reactive bonding agent with surface modification agent were then injected into the platform to fill the micron- and millimeter-sized channels and reservoirs, as well as the gap between the platform and the lid. Nitrogen gas was pumped in to replace most of the resin inside the channels and reservoirs. Resins can be cured by ultraviolet light, thermal, or redo initiation depending on the type of initiator. No leakage and blockage of the microchannel by using applying this technique and a very smooth channel sidewall was achieved as shown in Figure 1. The sharp corner of the reservoir can be rounded like a streamline, which may facilitate the fluid flow .
This resin-gas injection technique could also be used to form a layer of crosslinked polyacrylamide gel on the walls of the microchannel, serving as a sieving material for DNA separation by electrophoresis. The sieving material is one of the most important components in DNA sequencing analysis because it determines the migration behavior and the resolution of DNA separation. Difficulties are often experienced during loading the widely used sieving materials, linear polymer, because the presence of polymer greatly increases the viscosity of the solution. Air bubbles tend to be trapped in the microchannel, which is problematic in the electrophoresis process. External pumping (vortex or vacuum) is often necessary to assist the loading of sieving material and eliminate the air bubbles in separation channels. By applying resin-gas injection technique, only very low viscosity monomer solution need load into microchannel. The technique achieved similar DNA separation efficiency to the linear polymer solution, but eliminates the tedious sieving solution preparation procedure and facilitated the sample loading process , and achieved similar DNA separation efficiency to the linear polymer solution as shown in Figure 2.
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