Effects of polydimethylsiloxane (PDMS) microchannels on surface acoustic wave-based microfluidic devices

• The effects of PDMS microchannel on SAW-based microfluidic device are investigated.
• The SAW insertion loss is reduced as PDMS channel wall thickness decreases.
• The side wall is more critical than top wall to reduce the insertion loss.
• The particle migration velocity increases as PDMS channel wall thickness decreases.

Polymers are ideal microfluidic channel materials due to their chemical and biological compatibility, optical characteristics, fast and easy prototyping capability, and low fabrication cost. Especially, polydimethylsiloxane (PDMS) is the most widely used polymer as a microfluidic channel material due to many prominent features. However, this elastomer material severely attenuates Rayleigh surface acoustic waves (SAW) when they propagate toward the sample fluid within the microfluidic channel. The acoustic energy absorption by the microchannel affects the capabilities and efficiencies of the Rayleigh SAW-based microfluidic devices. In this paper, we investigate the effects of the PDMS channel wall thickness on the insertion loss and the particle migration to the pressure node due to acoustic radiation forces induced by Rayleigh SAW. Our results indicate that as the PDMS channel wall thickness decreased, the SAW insertion loss is reduced as well as the velocity of the particle migration due to acoustic forces increased significantly. As an example, reducing the side wall thickness of the PDMS channel from 8 to 2 mm in the design results in 31.2% decrease and 186% increase in the insertion loss and the particle migration velocity, respectively.

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