Fluorescent Environmental Monitoring with a Portable Temperature Control Module
Authors: Robertson Brianna , Shin Young-Ho , Choi Jin-Woo 
Published: December 2020

Fluorescent environmental monitoring has become an important aspect in understanding the vitality of regions affected by pollution, whether from natural or manmade sources. However, in order to effectively interpret the status of the environment, scientist often collect samples and return to their labs to process, sacrificing time and the vitality of the samples as a function of the distance travelled and the travelling conditions. Moreover, in-field detection methods, although effective, are subject to environmental factors that on which fluorescent detection is dependent, like temperature. In order to combat this, we propose a 3D-printed copper cuvette holder (i.materialise, Belgium) joined with Peltier-based temperature controller platform for stable reading of fluorescence emission from on-site solutions. To validate our system’s efficiency in temperature control in a lab setting, rhodamine B, which is one of the widely used fluorescence standards and probes in bioscience, was used [3]. Fluorescence dyes are widely used in biomolecule detection/quantification, flow tracing reference for gases and liquids, pathogen detection, and other life science applications [1, 2]. However, fluorescence emission efficiency of the dyes is easily affected by several parameters, such as polarity, pH, and temperature. Therefore, it is essential to monitor and control these parameters for reliable and accurate measurements, and with our device, we show this.
For excitation, 553 nm wavelength lighting was utilized for stimulating the rhodamine B. A Peltier device was controlled with different levels of direct current (DC) to demonstrate the temperature controlling capability of the device and fluorescence efficiency of the rhodamine B was tested with a varying temperature level: 25 ºC to 62 ºC. For our device, the temperature will be monitored by temperature ICs that are attached at three different points of the copper body for uniform temperature heating of the solution in a cuvette. Using these three surface-mounted MCP9808 temperature sensors, we determine the uniformity of the temperature across the copper cuvette holder, determining that the temperature is maintained within 1ºC. We monitored the solution temperature directly with the use of an infrared temperature sensor positioned down at the opening of the cuvette. The ambient temperature was monitored through the use of an thermocouples. An analysis of several different temperature components of the device allow for a better interpretation of what is happening in the system. Moreover, the implementation of a water-cooling apparatus allows for a way to quickly decrease the temperature of the cuvette when desirable, which is especially critical in high-ambient temperature environments. These features allow for the sample to be monitored efficiently, allowing for proper stabilization techniques and the ability to fluctuate the temperature when required of an application.
Now, we propose a series of tests that remove our device from a lab setting and into an environmentally accurate location. With a stabilized ambient temperature of 45 ºC, we intend to measure the fluorescence of rhodamine B as the solution reaches a stabilized equilibrium. We will then test our module’s reaction to a varying ambient temperature. Finally, as a final interpretation of our temperature control module’s portability, we will analyze the power consumption of our device in various temperature environments, along with an assessment of how humidity affects our platform. This will be accomplished through implementing our device in an external lab environment, which then we will record the humidity along with a real-time analysis of the fluorescent measurements as the solution stabilizes.
In summary, we have developed an 3D-printed copper cuvette holder with Peltier-based temperature controller platform for stable reading of fluorescence emission during different environmental atmospheres. Our compact temperature controller system provides viable option for any fluorometers to easily apply it for temperature stabilization during the fluorescence emission scanning.
References
[1] Dai, C. et al. American Journal of Infection Control, 43, 78-81 (2015)
[2] Wu, S., Duan, N., Shi, Z., Fang, C. and Wang, Z. Analytical chemistry, 86, 3100-3107 (2014)
[3] Kubin, R. F. & Fletcher, A. N. Journal of Luminescence, 27, 455–462 (1982)

Figure 1