137. ultrafast fluid spinning and particles centrifugation in a sessile drop using surface acoustic waves actuation by novel spiral interdigital transducers

Department: Mechanical & Aerospace Engineering
Faculty Advisor(s): James R. Friend

Primary Student
Name: Naiqing Zhang
Email: naz016@ucsd.edu
Phone: 619-381-0931
Grad Year: 2021

Abstract
The concept of lab-on-a-chip has been presented in recent decades. Various designs have been developed for manipulation of sessile drops and fluids in microchannels. Herein, we present a novel spiral design to perform ultrafast fluid spinning and particles centrifugation in a microliter sessile drop. Surface acoustic waves (SAWs) are generated by applying alternating current in radio frequency range onto interdigital transducers (IDTs) on piezoelectric materials, and a custom spiral equation is designed for SAWs rotational symmetrically propagating into the sessile drop with a constant angle. 3D Rotational traveling SAW animation has been shown on the droplet setting region via Laser Doppler Vibrometer. Our novel spiral device performed ultrafast fluid spinning up to 3000rpm inside the sessile drop, and rapid complete mixing with microliter dyed glycerol and water drop within one second. Size-based separation of polystyrene particles is rapidly performed by actuating SAW into drop. Due to the proportional relationship between acoustic radiation force and particle radius to the power of 6, bigger particles (40um) concentrated in the middle of drop due to its acoustic radiation force, while smaller particles (5um) concentrated at the periphery of drop due to its centrifugal force. Furthermore, a novel two-frequency spiral design has been developed for frequency-based manipulation of microparticles in a sessile drop. Particles performed different patterns in drop due to different radio frequencies applied on the spiral IDTs. Future possible applications based on our novel ultrafast spinning and centrifugation device can be focused on (1) whole blood ultrafast centrifugation to separate white blood cells and red blood cells from plasma, (2) point-of-care diagnostics using portable device with requirement of only tiny amount of blood, (3) rapid mixing in microsystems for further integration of biological and chemical processing.

Industry Application Area(s)
Life Sciences/Medical Devices & Instruments | Materials

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