Team:British Columbia/Hardware

• PROJECT

  • 
  • Inspiration
  • Description
  • Approach
  • Hardware
  • Results
  • Parts
  • Future
• LABORATORY
  • 
  • Experimental Design
  • Protocols
  • Notebook
  • Safety
• MODEL
• HUMAN PRACTICES

  • 
  • Integrated Human Practices
  • Education/Outreach
  • Collaborations
• TEAM

  • 
  • Team
  • Attributions
  • Sponsors
• MEDALS

Introduction

We envisioned our project to be in the form of a cheap, easy to use fluorometer that would be compatible with our saxitoxin biosensor. For this to work, the design of our prototype revolves around accessibility and reliability, with simple improvements on well tested frameworks. Our device was envisioned to measure the fluorescence of our biosensor, using either a whole-cell system or a cell free system delivered by a disposable vessel (ex. paper matrix) that would be inserted into the device. The device would then measure the fluorescence of the biosensor (generated by a reporter gene following the induction of our promoter with the substrate). The data would be displayed through an output such as an LCD screen, as well as saved in an SD card or a USB flash drive.

Circuit

Our circuit is simply designed, with a few major components including: the LED, optical sensor (photodiode), op-amp + low pass filter, and a microcontroller (arduino).

We will be using an LED as the excitation source for our biosensor. Since we will be detecting GFP, the LED must be selected to match the 475 nm excitation wavelength. Resistors must be added to prevent the LED from being overloaded (cannot have more than 3.3 V passing through the LED).

To measure the fluorescence, an optical sensor (a simple photodiode) will be used. It needs to be chosen on spectral characteristics as well, specifically in the 490nm to 550nm range. Emission/excitation filters can be added to increase the accuracy of the readings.

For the design of the circuit itself, we added an electronic filter. This was done through combining a capacitor and resistor in parallel, creating an electronic component called the low-pass filter. This is paired with an Op-amp to create a feed-back loop, allowing for each generated signal to return to the filter. The Om-amp is an inverting Op-amp due to it being safer than connecting to the positive terminal for low frequencies. The integration of a low-pass filter is to help clean up the frequencies received, removing the unwanted background frequencies (higher frequencies than a certain threshold).

The arduino used will provide the digital output and the current. The digital output will be used to turn on the LED and, on the other side, the optical sensor is connected to an analog input to receive voltages/signal.

Code/Script

Currently our code initializes all the pinouts and serial terminal of the arduino. With the continuous loop is programmed to take readings and plot data points. It is set with a 100ms delay between each data point for coherence.