Alan Renaudin

Removal of living cells from biosensing surfaces in droplet-based microfluidics using surface acoustic waves

Removal of living biological cells from surfaces is a critical process for many applications in the area of biosensing and lab-on-a-chip. Trypsin is one of the most effective biochemical tools used to cleave the cells proteins that are responsible for bonding cells to surfaces [1]. We propose a method using Rayleigh-type (20MHz) surface acoustic wave (SAW)-based mixing [2] as an accelerator for trypsin mediated removal of living cells from surfaces. In the experiments, a 10 µL droplet of Hanks Balanced Salt Solution (HBSS)-trypsin is placed on a piezoelectric substrate covered with human embryonic kidney cells (HEK293). Using phase contrast microscopy, cells removal time for different acoustic power levels and trypsin concentrations is measured. Results from validation experiments show that a minimum of 180 seconds is necessary to completely release surface-bonded cells covered by the 10µL droplet without the use of SAW (negative control). By using microstreaming flow in the droplets generated by the SAW...

Accelerated binding kinetics by surface acoustic waves (SAW) micromixing in surface plasmon resonance (SPR) system for biodetection

A design incorporating surface plasmon resonance (SPR) biosensing and surface acoustic wave (SAW) active microfluidic mixing, integrated on a single LiNbO3 piezoelectric substrate, is presented. Validation experiments show that SAW-mixing (microstreaming) results in accelerated binding kinetics (time-to-saturation) for a standard assay with appropriate SAW excitation parameters. Since both SPR sensors and SAW transducers can be fabricated simultaneously using low-cost microfabrication methods, the proposed design should contribute to improved lab-on-chip devices for detecting and identifying biomolecules of interest with greater accuracy and speed across multiple applications.

Surface acoustic waves (SAW) accelerated microfluidic mixing for improved microcalorimetry in biochips

By measuring very small local temperature changes, microcalorimetry is used to determine the rates of energy released or absorbed during biochemical reactions. The measurement signal-to-noise ratio can be significantly increased by accelerating the reaction kinetics by active microfluidic mixing. We present a biochip incorporating a self-referencing droplet-based microreactor consisting of a thermopile-based microcalorimeter (50 Ni/Au thermocouples in series) on a glass substrate with a surface acoustic wave (SAW)-based microfluidic mixing system on a LiNbO3 piezoelectric substrate. In our design, the SAW mechanical energy is transmitted from the piezoelectric substrate through the glass substrate to the droplets via a water film which acts as a pseudo mechanical impedance matching layer. The cumulative energy released by a standard calorimetric test reaction (sucrose dilution) is measured with the system. Results show that, by overcoming the diffusion-limited reaction rate, SAW-accelerated mixing in the ...

Accelerated surface plasmon resonance biosensing by surface acoustic waves microstreaming

This paper describes our design incorporating surface plasmon resonance biosensing and surface acoustic wave active microfluidic mixing, integrated on a single LiNbO3 piezoelectric substrate. Validation experiments show that surface acoustic wave-induced microstreaming results in significant accelerated binding kinetics in a case of a standard avidin-biotin affinity assay.