Introduction/Abstract
The 2021 SUNY Oneonta iGEM project focused on creating a field deployable detection system for favorable genetic traits in cattle. Our detection system required a simple portable heating device that can be easily used in the field. Scientists often need to control the temperature of the samples in their experiments. They can do this in a variety of ways, including putting their sample on ice, in an oven, in a heated water bath, or in a device called a heat block. A heat block is a block of metal with holes drilled in it to fit samples. The temperature is regulated by controlling the amount of electrical power that flows through a thermocouple in contact with the heat block.
The 2020 team designed a single heat block prototype using easily accessible and low-cost parts. Our device was tested by middle school students at a virtual summer science camp that we ran, in which participants were mailed kits of materials for at-home experiments. Students were able to successfully assemble and use the heat block, but the temperature control was unreliable. This year, we decided to improve our heat block design while keeping our goals of using easily obtained and inexpensive components. For our 2021 project, we decided to develop a procedure to quantitatively evaluate the performance of each prototype produced as we iterated our design to develop a more stably functioning piece of hardware. During the process, we opted to switch the controller on the heat block from an aquarium temperature controller to a Raspberry Pi-based device.
The experimental procedure was designed to:
- Test the heat block’s ability to reach a specific temperature quickly and safely
- Demonstrate that the heat block can remain at a constant temperature during an experiment
- Affirm that the heat block can cool down quickly and safely
Prototype Testing Objectives and Method Overview:
Target Temperature
- This first step tested the amount of time it took for the heat block to reach a predetermined temperature. The target temperature was set to 37°C. The temperature was recorded every 30 seconds for 360 seconds (about 6 minutes). Stability
- The second step tested the ability of the heat block to maintain a set temperature for the allocated time. Once it achieved the target temperature, the temperature of the heat block was recorded every 30 seconds for 360 seconds (about 6 minutes).
Cool Down Performance - The third step tested the effectiveness of the heat block’s ability to cool down from its target temperature. The temperature was recorded every 30 seconds for 360 seconds (about 6 minutes) or until the heat block reached the recorded room temperature.
Software Development
Hardware Integration
Utilizing a Raspberry Pi 3B as a Programmable Logic Controller as well as I/O sensors, we were able to successfully utilize automation algorithms to detect and regulate temperature on the heat block.
Target Temperature Detection and Regulation
To control the Peltier Chip, we utilized Python Scripting to control a low power current which functioned as the base of a transistor circuit. When the attached temperature sensor was reading below the desired temperature, an electrical current was sent from the Raspberry Pi to toggle the Peltier Chip on. Once the temperature sensor indicated that the Heat Block was at or above the desired temperature, the current was terminated which toggled the Peltier Chip off.
Visual indicators in the form of Green and Red LEDs were utilized to inform the user that the Heat Block was either at the desired temperature (Green) or it was adjusting to the new parameters (Red).
Further Development In the coming months, we plan to further develop this device by adding fans to assist in temperature regulation, specifically in more rapidly reducing the temperature of the heat block in the event that the Peltier Chip overheats.
Figure 1: Schematic Diagram of Raspberry Pi Implementation Within a Transistor Circut. LED Diodes were used for testing and debugging purposes and later switched to the Peltier Chip for heat regulation.
Heat Block Prototype Designs & Parts
The following prototypes were inspired by the SUNY Oneonta 2020 iGEM team heat block prototype. We decided to begin by using the same components to regulate heat of the Peltier chip and the same structure to hold the sample as in our 2020 prototype.
Each heat block included:
- INKBIRD temperature controller with temperature probe (Part #1)
- Aluminum Block (Part #2)
- Kastar AC adapter and end adapter (Part #3)
- Aluminum block holder (Part #4)
- AC/Peltier Adapter (Part #5)
Peltier Chips are a thermoelectric device commonly used in cooling, heating, or control of temperature. An electric current flow through the junctions of the two conductors, heat is then removed from one junction and cooling the other opposite side. Heat is then released at the other junction. Our heat block device uses a Peltier chip as its heat source.
Figure 2: Heat flow in a Peltier chip. Red arrows indicate heat, blue arrows indicate cooling.
Heat Sinks are a component used to increase the heat flow away from a hot device. The comb-like structure increases the surface area which creates an efficient path for heat to escape. This component is primarily found in computer systems paired with a fan to redirect heat.
Figure 3: Heat sink added to a Peltier chip. Arrows indicate heat flowing away from the chip, cooling the device.
a) Prototype 1
a) Prototype 2
a) Prototype 3
Figure 4: Schematics of heat block prototypes. Numbers of individual parts correspond to the parts listed in the “Parts Catalog.” (a.) Initial heat block design (b.) Design that included a different heating chip (c.) Design which incorporated a heat sink.
Figure 5: Heat Block Full Part Catalog