Polymer bonding by induction heating for microfluidic applications

Microfluidic systems are being used in many applications and the demand for such systems has been phenomenal in past decades. To meet such high volume market needs, a cheap and rapid method for sealing these microfluidic platforms which is viable for mass manufacture is highly desirable. The packaging must protect the system against dirt, humidity, stresses, etc and, depending on the application, provide electrical, fluidic or optical interconnection and thermal management. Most of the existing sealing and interconnecting techniques are cost-intensive and slow compared to the other manufacturing steps of the microfluidic system, so that they form a bottleneck in mass production. Low frequency induction heating (LFIH) has been introduced as potential basis of a cost-effective, rapid production method for polymer microfluidic device sealing in preceding publications. Induction heating is well established in the steel industry for hardening, melting, soldering, welding, and annealing, but increasingly is finding application in other areas like heating fillings in dental medicine, and cap sealing. Through this technique excellent bond strength was achieved, withstanding an air-pressure of up to 590 kPa. However, it has been found that during the bonding process it is important to effectively manage the heat dissipation to prevent distortion of the microfluidic platform. The heat affected zone, and the localised melted area, must be controlled to avoid blockage of the microfluidic channels or altering the channels' wall characteristics. This work sums up the results of experiments, simulations and analytical approaches to provide a basis for process optimisation. The effects of susceptor area and bond parameters like bond pressure and heating time on the heating rate are discussed. Heat affected zone and bond strength of pulse heated samples are compared to those of continuously heated systems and rules for susceptor design are provided. Based on the knowledge gained a microfluidic device is designed and manufactured.