Packaging of Microfluidic Devices for Fluid Interconnection Using Thermoplastics

A new packaging method for microfluidic devices is proposed of polymer over-molding to form a fluidic manifold integrated with the device in a single step. The anticipated advantages of the proposed method of packaging are ease of assembly and low part count, making it suitable for low cost and high volume manufacturing. This paper reports the results of a preliminary investigation into this concept. Glass and silicon inserts of 25 times 20 mm in size, used to represent microfluidic devices, were over-molded in an injection molding process with a range of polymers. The inserts were found to survive the molding process intact. The adhesion between overmold and insert was investigated by subjecting the interface between the overmold and insert surface to a hydrostatic pressure of up to 100 lbf/in² (6.9 bar). The durability of the interfacial adhesion to hydrolysis was investigated by immersion in water at 50degC for 24 h before testing. Direct measurements of adhesion strength between polymer and glass were also attempted by tensile tests on lap-jointed samples. The best and most durable adhesion for glass and silicon inserts was found for polyamide (PA) 12, which is a low hygroscopicity PA. The ranking of polymers by their performances in the pressurization tests was consistent with the ranking by the calculated work-of-adhesion values for polymer/glass and polymer/silicon joints.