Flexible Acoustic Particle Manipulation Device with Integrated Optical Waveguide for Enhanced Microbead Assays

Abstract

Realisation of a device intended for the manipulation and detection of bead-tagged DNA and other bio-molecules is presented. Acoustic radiation forces are used to manipulate polystyrene micro-beads into an optical evanescent field generated by a laser pumped ion-exchanged waveguide. The evanescent field only excites fluorophores brought within ~100 nm of the waveguide, allowing the system to differentiate between targets bound to the beads and those unbound and still held in suspension. The radiation forces are generated in a standing-wave chamber that supports multiple acoustic modes, permitting particles to be both attracted to the waveguide surface and also repelled. To provide further control over particle position, a novel method of switching rapidly between different acoustic modes is demonstrated, through which particles are manipulated into an arbitrary position within the chamber. A novel type of assay is presented: a mixture of streptavidin coated and control beads are driven towards a biotin functionalised surface, then a repulsive force is applied, making it possible to determine which beads became bound to the surface. It is shown that the quarter-wave mode can enhance bead to surface interaction, overcoming potential barriers caused by surface charges. It is demonstrated that by measuring the time of flight of a microsphere across the device the bead size can be determined, providing a means of multiplexing the detection, potentially detecting a range of different target molecules, or varying bead mass.

Contrast agent-free sonoporation: The use of an ultrasonic standing wave microfluidic system for the delivery of pharmaceutical agents

“…capillary was measured through a drop-voltage analysis, using 20 lm diameter fluorescent polystyrene beads. 34 Polyofelin heat shrink tubing was used to stabilize silicon inlet and outlet tubing (1.6 mm OD, 1 mm ID) for fluid delivery and release [ Fig. 1(b)].…”

Acoustofluidics 9: Modelling and applications of planar resonant devices for acoustic particle manipulation

“…By using suitable symmetry conditions a 1D model can be created; Fig. 3 compares the transfer impedance model with a KLM transducer representation to an ANSYS FEA model for a typical quarter-wave configuration (presented elsewhere 30 ), and shows good agreement. Small inconsistencies are to be expected due the differences in the ways the models implement the damping and transducer 45 representation.…”

“…The Mason model configuration is presented in Fig. 2; the values of the parameters can be found 30 elsewhere 24 . The Mason model is derived from the constitutive piezoelectric relations described in part 4 of this tutorial series 25 .…”

“…In order to visualise the optimisation of the three variables Fig. 6 is plotted first 30 for the case when there is no carrier layer, then for a λ/4 reflector layer. It can be seen that the optimum combination is for a fluid layer of 360 µm, reflector layer 800 µm thick, and zero carrier layer.…”

“…The potential energy density gradient (a function of the acoustic pressure within the standing wave) is weighted by a function of the compressibilities ( p  and f  ) of the particle and the surrounding fluid. Most particles and cells of interest are denser and less compressible than typical suspending fluid, so there is a force 30 on them that tends to move them to the acoustic pressure node, and the acoustic velocity antinode. In a planar resonator these are colocated.…”