Ultrasonic bonding for thermoplastic microfluidic devices without energy director

Thermal assisted ultrasonic bonding and solvent assisted ultrasonic bonding for thermoplastic microfluidic devices are proposed in this paper. Both of these two methods are non-molten bonding, energy director is not employed and thus avoided the problem of controlling the molten polymer flow along the microstructure during bonding process. Ultrasonic bonding system and interfacial temperature testing system were established. The critical amplitude for bonding was chosen by interfacial temperature tests to keep the bonding interface below glass transition temperature (T-g) of the polymer. Polymethylmethacrylate (PMMA) microfluidic devices were bonded by both thermal assisted ultrasonic bonding and solvent assisted ultrasonic bonding with the bonding time of 30 s and 20 s, respectively, while the tensile strength of 0.95 MPa and 2.25 MPa, respectively. The bonding area was 27 mm x 51 mm, the maximum dimension loss for the microstructure was 0.66% +/- 0.60. A four-layer PMMA microfluidic device was also bonded using thermal assisted ultrasonic bonding, demonstrated the advantage of localized heating character of ultrasonic bonding and did some preliminary work in multilayer polymer MEMS device bonding. This paper provided the potential high throughput bonding methods for mass production of polymer microfluidic devices. (C) 2010 Elsevier B.V. All rights reserved.