Media 4: Particle size limits when using optical trapping and deflection of particles for sorting using diode laser bars

Originally published in Optics Express on 14 September 2009 (oe-17-19-16731

Media 2: Particle size limits when using optical trapping and deflection of particles for sorting using diode laser bars

Originally published in Optics Express on 14 September 2009 (oe-17-19-16731

Media 1: Particle size limits when using optical trapping and deflection of particles for sorting using diode laser bars

Originally published in Optics Express on 14 September 2009 (oe-17-19-16731

Media 3: Particle size limits when using optical trapping and deflection of particles for sorting using diode laser bars

Originally published in Optics Express on 14 September 2009 (oe-17-19-16731

Power dependence to focusing width in etched silica device.

For the Si etched device at low input power there was a single frequency bandwidth around 1.175 MHz that resulted in optimal focusing performance. At the high power level there were multiple local minima of high focusing performance.</p

Schematic of the two acoustic focusing devices and their optical analysis points.

Within both of these systems, the one-dimensional focusing of particles was monitored downstream of the driving PZT. Both of these systems were driven at their fundamental half-wavelength mode, represented by the blue dashed lines in B top, which focused the particles into a single central node. The focusing performance of the capillary (A) was monitored through transparent tubing at the end of the device while the etched-through Si wafer (B) is monitored just downstream of the PZT.</p

Focusing width vs frequency for three input power levels within the cylindrical capillary system.

At the highest input power levels there was tight focusing across a wide frequency space, while at the lowest input power there was tight focusing (less than ~20 μm) across a small frequency bandwidth of a few kHz.</p

Optimal focusing frequency over a range of media salinities within the capillary system.

The five blue scatter points were experimentally determined at each salinity while the red line plot represents a simple model that assumes that the speed of sound within the liquid media alone determines these resonance frequency shifts.</p

Focusing width and conductance in Si system.

Calibrated impedance (A) and conductance (B) scans are shown overlaid with acoustic focusing width. A local conductance max (impedance minima) was correlated with the best performing driving frequency (1.179 MHz). The overlaid blue and red circles were selected from the focusing data alone, demonstrating near perfect correlation between the conductance maxima and focusing minima. Note that there were additional conductance peaks that could otherwise be indistinguishable from the optimal frequency if the search bandwidth was not limited.</p

Quantification of focusing.

For a model system of fluorescent 10- μm beads (Sky Blue FP-10070-2, Spherotech), an example of poorly focused (left) and well-focused image data (right). Each image shown here was constructed from a summed stack of 500 individual images taken over ~30s of data at a single frequency condition. The focusing width of each summed image was fit to a Gaussian curve using MATLAB and the width at half-maximum was used as a representative focusing width. Applying this process across an iterative frequency scan for a single temperature yields an experimental method of measuring the optimal resonance frequency condition. Repeating this process at a variety of temperatures allowed for the experimental characterisation the highest performing resonance frequencies as a function of temperature.</p