Title:

"Acoustic Microstreaming by a Pinned, Oscillating Membrane, Antifouling PDMS, and Application to Microfluidic Artificial Lung”

ABSTRACT:

Acoustic microstreaming in microfluidic devices is often used as a means to disrupt the typically laminar flows seen at the micro-scale for various purposes such as mixing and propulsion. Lower, audible frequency configurations can be cheaper and easier to generate, but are more limited in transduction methods due to the very long acoustic wavelengths. Existing audible frequency methods such as bubble and sharp edge streaming suffer from disadvantages of stability and obstruction.

In this proposal, a new configuration to generate acoustic streaming at audible frequency in a microchannel by a pinned oscillating membrane is described and characterized. Advanced characterization methods and CFD simulation show similar pattern and magnitude, providing evidence that this membrane oscillation is the primary driving mechanism of the time-averaged flow. This method has potential application to the technology of the microfluidic artificial lung due to the vertical orientation of the resulting mixing allowing for augmentation of gas exchange across a permeable membrane, stability, and lack of any obstruction. Successful augmentation of gas exchange is demonstrated as shown by characterization of CO₂ transferred into the liquid water channel.

Also, development and characterization of a modification of PDMS, called PDMS-SB, is shown which offers improved hemocompatibility as evidenced by reduced coagulation and biofouling by deposition in a microchannel. The PDMS-SB is able to be easily integrated into existing and future fabrication processes designed for commercial PDMS as shown by compatibility with standard techniques such as spin coating, soft lithography, and plasma bonding as well as showing similar mechanical properties and keeping gas permeability of a membrane sample.

Continued work in these topics are focused on bringing the concept closer to the intended end application of the microfluidic artificial lung. Advancements in device design and fabrication will be studied towards scaling up of the gas transfer device to allow for parallel flows and therefore increased throughput at a given concentration for gas transfer. The end goal is integration of the physical phenomenon and device design with blood flow, the most critical step towards the end application. Characterization of hemocompatibility of the flow will be studied by characterization of coagulation response and biofouling by deposition for microchannel flow with the induced acoustic streaming. Gas transfer experiments will then be adapted to blood flow. Then, integration of this experiment with PDMS-SB will be considered in an attempt to configure the best possible device in terms of performance and hemocompatibility.

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Meeting ID: 925 5767 6227