Acoustothermal heating of polydimethylsiloxane microfluidic system

Abstract

We report an observation of rapid (exceeding 2,000 K/s) heating of polydimethylsiloxane (PDMS), one of the most popular microchannel materials, under cyclic loadings at high (~MHz) frequencies. A microheater was developed based on the finding. The heating mechanism utilized vibration damping in PDMS induced by sound waves that were generated and precisely controlled using a conventional surface acoustic wave (SAW) microfluidic system. The refraction of SAW into the PDMS microchip, called the leaky SAW, takes a form of bulk wave and rapidly heats the microchannels in a volumetric manner. The penetration depths were measured to range from 210 μm to 1290 μm, enough to cover most sizes of microchannels. The energy conversion efficiency was SAW frequency-dependent and measured to be the highest at around 30 MHz. Independent actuation of each interdigital transducer (IDT) enabled independent manipulation of SAWs, permitting spatiotemporal control of temperature on the microchip. All the advantages of this microheater facilitated a two-step continuous flow polymerase chain reaction (CFPCR) to achieve the billion-fold amplification of a 134 bp DNA amplicon in less than 3 min.

Modeling of Microdevices for SAW-Based Acoustophoresis — A Study of Boundary Conditions

“…Modeling of acoustofluidic devices should thus be performed in full to take into account all effects relating to the elastic walls defining the microchannel. At higher frequencies or higher acoustic power levels, even the full model presented here must be extended to take into account thermoviscous effects in the form of increased heating and temperature-depending effects [ 44 , 54 ]. Finally, to obtain quantitatively better results for the pressure fields driving acoustophoresis in the water domain, the piezoelectric substrate should be included in future simulations.…”

Two-dimensional single-cell patterning with one cell per well driven by surface acoustic waves

“…For analysis, the cultures are synchronised to ring stages using 5% sorbitol 67 and collected 24 h later. Temperatures of 35±2 °C are maintained on the microfluidic chip via a thermoelectric device on which the OCPW system is mounted, where steady-state temperatures are typically achieved on the order of seconds 68 69 .…”

Forming three-dimensional closed shapes from two-dimensional soft ribbons by controlled buckling

“…Figure 1 a , b presents various 3D thin-walled structures with closed surfaces, each transformed from corresponding eight or 16 pieces of 2D elastic ribbons of elastomer, such as polydimethylsiloxane (PDMS, transparent) and thermoplastic olefin (TPO, black colour). Those ribbons are fabricated by a standard casting process [ 24 – 26 ] (see Material and methods) with a variety of patterns engraved on the surfaces to enhance flexibility in certain orientations and/or specific locations [ 17 ]. The primary patterns used are line partial cuts and linearly varying thickness.…”