Weeks 2 and 3 Update

Throughout both of these weeks, I learned more about the technology I am developing while continuing my research on  cyanobacteria and cyanotoxins. The microsensors I am building worked by creating an evanescent field around a microtoroid by coupling an electromag magnetic wave from an optical fiber. The basic structure of the system is show below.Microtorid structure

In the above image, the electromagnetic wave resonates around the microtoroid at a measurable wavelength, creating the evanescent field. In order to allow the optical fiber to couple light to the silica toroid, the cladding is removed so that total internal reflection no longer occurs. Below is a diagram of an optical fiber.Optical fiber diagram

When particles bind to the surface of the toroid, the resonant wavelength changes and the energy being coupled from the fiber changes as well. This effect is measurable and can produce data such as the graph below.Resonant shifting

Each singular shift in this graph is a particle binding. The units of the shift in wavelength are femtometers or a quadrillionth of a meter. Each of the shifts is miniscule because relative to the size of the microtoroid, the particles are tiny. Below is an image of a microtoroid.

Microtorid image

The toroid has about the diameter of a human hair to put the image into perspective. Since the toroid is so small, bacteria will not bind to the structure effectively. Instead of focusing on the bacteria, I began to focus my research on the chemical outputs of cyanobacteria. In doing so, I found that there are several common cyanobacteria that produce a wide range of toxins of similar structure. The species is Microcystis which produces microcystin, a liver  toxin that may also be a carcinogen. There are approximately 80 know microcystins all of which have varying levels of toxicity. I also found a toxin called BMAA (beta-Methylamino-L-alanine) which is produced by a majority of cyanobacteria, but is more difficult to detect.

When I begin my lab work, I will be using the same concept of detection but instead of using microtoroids, I will be using optical spheres made by melting optical fiber with a laser. They bend light in the same fashion as the toroid but can be produced using the equipment at hand at the University of Arizona.


3 thoughts on “Weeks 2 and 3 Update

  1. Looks like you are enjoying the hands-on work and the images are definitely helpful for those of us who are not familiar with your equipment/research. Did you choose cyanobacteria to work with for a particular reason or because of your lab’s requirements? What do you hope the longer term goals of the research will be?


    1. I choose cyanobacteria because I was interested in the potential use of microresonators in water quality tests. The goal of the research I’m doing is to show that using antibodies as an agent to increase specificity of the sensors, cyanotoxins can be detected in water. Hopefully by the time my SRP ends, I will have shown this to work. Recently, a microelectronics company came through the lab interested in the microtoroids and their potential uses. The long term goal of this research is to produce portable sensors that require no training and produce results almost instantaneously. Molecular tests such as ELISA and UV detection techniques are expensive concerning time, money, and training.


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