Micro-ultrasonic welding using thermoplastic-elastomeric composite film

A composite film of PMMA microspheres in PDMS is used as the fusion layer to avoid trapped air and to restrict the flow of the melted polymer during welding. The matrix material selection and distribution of PMMA microspheres is determined by the 1-D theoretical model. The theoretical work reveals that the difference in dynamic modulus between the matrix material and PMMA is the most significant contribution to the viability of this composite ultrasonic welding film. The experiment is conducted with PDMS as the matrix material to determine effect of the concentration of PMMA microspheres as micro energy directors on the welding strength and quality of the proposed methodology with the chosen composite. While there are no visible signs of trapped air in all specimens, the resultant welding strength in this methodology is limited by the particle size range of the PMMA microspheres. For ultrasonic energy input of 1 kJ on a 32 mm × 32 mm sample, the optimum concentration of PMMA microspheres is found to be 0.24.