Micro energy director array in ultrasonic precise bonding for thermoplastic micro assembly

A new ultrasonic precise bonding method was designed for the assembly of thermalplastic microfluidic devices. In this method the process was controlled by monitoring the mechanical behavior of thermoplastic components, which was realized by measuring the attenuation of ultrasound propagation. Micro energy director array was proposed for this bonding method. By fabricating array of micro energy directors in rectangular pyramid shape on one of the bonding surfaces the contact area was reduced. So it concentrated ultrasound in smaller area and also provided extra space for the spread of the polymer in viscous state, which was beneficial to improve the utilization of ultrasound and the interfacial fusion quality. Two characteristics of the micro energy director array including structure size and distribution size were studied in experiments. Results showed that at same bonding parameters the bonding degree was weakened by increasing the structure dimension and enhanced by increasing the distribution scale. With micro energy director array selected in proper size the interfacial fusion in high quality could be achieved in a wider parameter range, which made the bonding results more controllable.