Team:ITB Indonesia/Hardware
In principle, this device is a 'dressed-down' fluorescence spectrometer, akin to laboratory spectrometers. This device is inspired by various open-source spectrometry projects, chiefly the Public Lab Spectrometry Project [1]. The device uses two sets of lasers: a 600 nm laser (a) parallel to the sampling window to measure the absorbance of the sample, and a 485 nm laser (b) perpendicular to the sampling window to measure the fluorescence of the sample. Through the measurement of these two values, the device can be calibrated and used to determine the level of Vibrio parahaemolyticus in the shrimp pond. The device uses optical components, including a lens (c), a diffraction grating (d), and a camera (e). A Raspberry Pi (g) is used as the controller board. This device is controlled through a smartphone app, connected to the Raspberry Pi through the local network (wi-fi), enabling easy control and reading of the result by the user.
To use the device, the user inserts two cuvettes to the holder (h), one containing only the growth medium mixed with pond water sample and the other added with the engineered Escherichia coli. The first cuvette will be used to calibrate the device. The user then close the door, and through the smartphone app starts the measurement process with a click of a button. The controller board then activates the absorbance laser. The beam of light then passes through the slit, focused by the lens, and is split to its constituent wavelengths using the diffraction grating. A camera then captures the beam, and the controller board then determines the intensity of the beam, which is translated into the absorbance level. Through the same process, the fluorescence of the sample is measured by exciting the sample with the fluorescence laser. The controller board then process the data and calculate the Vibrio parahaemolyticus level. The data is sent to the smartphone app to be displayed to the user. After the measurement process, a specific volume made available with the purchase of the bacteria is mixed with the sample to kill the microorganisms.
Biosafety of this device is ensured by (1) locking the sample and all the measurement components inside a sealed compartment and requiring the user to close the sample door before starting the measurement, (2) using bleach to kill all microorganisms after the measurement process, and (3) developing a Standard Operating Procedure to assure the right use of the device.
[1] https://publiclab.org/wiki/spectrometry. CC-BY-SA 2018 Public Lab contributors.
