Below is a list of the research projects that have been of interest over the years. The list is mostly chronological with the newest first and consists largely of summaries. If you are interested in hearing more I will attempt to put citations or links for articles and you can always email me!
Even when the utmost care and effort is taken when designing an optical system, the resolution is fundamentally limited by diffraction. Passing through an aperture, be it the primary mirror on a telescope or the lens on your phone’s camera, causes the light to fuzz out. It might seem paradoxical, but the larger the opening that the light passes through, the less the light spreads out. This is a reason for the drive towards ever larger telescopes and microscope objectives with increasingly large numerical apertures.
However there are limits to how large one can make the limiting aperture in an imaging system be it from cost or other technical reasons. To my knowledge, Bessel Beam Microscope represents the first time that anyone has improved this limit when wide-field imaging without increasing the width of the imaging aperture. With a single acquisition, Bessel Beam Microscopy can increase the resolution of the imaging system by up to 40%. The results can be dramatic; as seen above individual particles that were previously indistinguishable can now be picked out with ease.
Recently I have also shown that these impressive resolution gains are possible with very little cost to overall image quality. Images with high brightness and reduced “haze” can easily be acquired as can be seen to the right without any post-processing of the images. Because only a single image is needed and that image is bright with high contrast, the Bessel Beam Microscopy system is capable of super-resolution imaging at speeds that are an order of magnitude faster then current technologies.
A persistent problem in microfluidics is a lack of three dimensional fluid velocity measurement techniques. The reasons for this lack are due largely to the small size of the flows involved. There simply isn’t room for multiple cameras or perspectives that are the mainstays of many macroscale 3D velocimetry techniques. As a result it is necessary to get clever and to make use of what information you have.
The result is a measurement technique I invented called Bessel Beam Microscopy. This technique is fairly unique because it doesn’t rely on distortions of the particle image to determine the depth of the particle. Instead, it transforms the particle’s wavefront into a Bessel beam and then uses several key features of the Bessel Beam to determine the three dimensional location of the particle. This has several advantages:
- Zero calibration. If you know the optical components of your imaging system you can plug it in and start taking measurements. Additionally, calibration is not the limiting factor when locating particles with very high depth resolution.
- Highly customizable measurement depth and resolution. I can easily achieve a measurement depth of over 500 um with a 10x lens or with that same objective a depth resolution on the order of 100 nm. This is easily customizable by changing key optical components of my design.
- Technique does not rely on a single particle feature. As a result my technique is insensitive to changes in particle size or intensity.
It turns out that sharks have many more tricks up their sleeves (fins?) for hunting fish then you would expect at first. At a really short range they can use their eyes and a set of electric field sensing pores along their flanks. At longer range they can use their sense of smell and what appears to be a super-sensitive ability to sense temperature gradients. How they sense these gradients was the subject of my research. We believed that the electrical sensing pores in the skin of sharks is filled with a gel that produces a very large voltage in response to temperature gradients. It was our hope that we could eventually harness the mechanism behind this large voltage in response to a temperature gradient (thermoelectricity) as an energy source.
The results of my research indicated that while the gel does indeed produce a very large voltage in response to temperature gradients this is a behavior typical of strongly ionic solutions. While that is somewhat disappointing I learned a tremendous amount about electro chemistry and the wonderful complexity of ionic solutions, something I hope to study further in the future.