Low-Thermal-Dissipation PDMS Package for Surface Acoustic Wave-Based Microfluidic Lab-on-Chip Devices
Abstract
The integration of polydimethylsiloxane (PDMS) microstructures with surface acoustic wave (SAW) devices requires controlled mechanical attachment to piezoelectric substrates, as mechanical boundary conditions directly influence the heating rate through acoustothermal energy dissipation. In this work, we propose a novel method for PDMS microstructure attachment that minimizes this effect. The approach is based on the selective bonding of regions of the microstructure that are not in direct contact with the SAW propagation path. Leakage from non-bonded regions is prevented by hydrophobization of the crystal surface. Temperature evolution was analyzed under different excitation voltages and time intervals to assess repeatability, stability, voltage dependence, and the validity of the proposed approach. The results show that the temperature rise scales approximately with the square of the applied voltage within the investigated range, consistent with a predominantly linear acoustothermal conversion regime. Sequential, time-separated measurements demonstrated reproducible thermal responses, with no evidence of significant degradation over a 24 -hour period. Comparative analysis revealed that directly bonded regions exhibit higher local temperature increases, while selectively non-bonded walls show reduced thermal dissipation, highlighting the influence of mechanical boundary conditions on acoustic energy distribution. These findings emphasize the importance of selective bonding strategies for controlling acoustothermal behavior and support the definition of predictable operational regimes in SAW-based lab-on-chip systems.