Hardware

First Iteration

When we first designed our first physical Bo-FIND device, we envisioned it being handheld containing all the heating elements and detection hardware. We 3D-printed this design and started brainstorming how it would function. We spoke with Amino Labs, a company devoted to making software, hardware, and learning resources to educate youth about genetic engineering and biotechnology, who advised us on improving our design. They suggested we really examine what our minimal viable product was for our product to function in the most basic sense. We also participated in the Tech Future Challenge, a competition run by MindFuel. The feedback we received from judges also helped us make revisions to our design. At the time, we had a rectangular box design. One slot where a microcentrifuge tube would be placed for the extraction portion of the amplification. Next to this slot were five smaller slots for microcentrifuge tubes containing the primers required for recombinase polymerase amplification (RPA). The fifth microcentrifuge tube was a control. From the feedback we received we moved onto our minimal viable product that included just heating elements that were controlled by two thermostats.

Second Iteration - Minimal Viable Product

Following our discussions with Amino Labs, our device design change to consist of only four main parts: an aluminum holder block for heating, a digital temperature controller, a PTC heating element, and a plug-in power supply. The PTC heater was powered by a 12V adapter. The University of Lethbridge in Alberta, Canada, has a technical services department that helped us drill holes into two aluminum blocks. These blocks would hold the microcentrifuge tubes that would be heated to 100℃ and 37℃ with the PTC heating unit. Dr Chad Povey from the University of Lethbridge physics department helped assemble the correct circuit for our first prototype. Our initial test was successful; the heating element did heat the aluminum holder. Although this prototype did work and did the basic task of heating our tubes, there were many more features we hoped to incorporate into the final Bo-FIND design.

Heating and Display

Since then, we have expanded our design and added many more parts. Our most current design has two separate heating elements. One is for the extraction microcentrifuge tubes, which will ensure they are heated to 100℃ for 10 minutes; the other is for the detection microcentrifuge tubes, which will be heated to 37℃ for 30 minutes. A timer will be displayed on the LCD 1602. Once the extraction step is complete and the initial DNA solution has been split into all five detection tubes, another 30-minute timer will begin, heating the four detection and control tubes to 37℃. Once this timer is complete, the user will be notified through the screen. The heating blocks will be kept separate from the rest of the circuitry to ensure no hardware is damaged. Furthermore, the heating elements surrounding the tubes must be insulated to ensure no damage to our device's internals and shell. Insulating will also be present between the two separate heating blocks to ensure that each of them doesn’t affect the temperature of the other. The entire device will be constructed from chitosan, a biodegradable, autoclavable material that can withstand temperatures up to 200℃.

The device will have a thermistor for two main uses. It will act as a safety feature to ensure that the temperature within the device stays within a reasonable range and is not affected by the PTC heating units. If the temperature goes above this number due to some kind of malfunction, it will trigger an automatic shutdown of the step occurring at the time. This will turn off the heating units, resulting in a reduction in temperature. The second use for the thermistor is to collect info regarding the temperature of the metal heating blocks and transmit it to the LDC 1602. This is how the user will know the temperature of each heating block during each testing step. The device will have an LCD 1602 screen to display a variety of visual instructions and progress information. The screen will turn on as soon as the device is turned on and will also turn off when the off button is pressed. The screen will show when a test step is complete so the user can press the necessary button to continue. The screen will display the temperatures of both the extraction and detection steps, a running-down timer that signifies the remaining time of a step, and word cues that show continuation instructions. The LCD1602 will work with a potentiometer 10k. This will be set while the device is constructed to ensure that the LCD1602 has good brightness and transparency.

Device Signals

Our detection device will have three lights on its surface representing different things. The red LED will be used to signify that the device has been turned off. Once the off button has been pressed, the light will blink red three times before turning off. This is how the user will know that the Bo-FIND device is off while not in use. If the device is on, the red LED light will be on for either the extraction or detection step to show that each testing step is incomplete. Once either step, the extraction or detection, is complete, a blue LED light will turn on and remain solid. It will stay on until the button to start the detection step has been pressed, then the red LED will turn on. Once the step has been completed, the blue LED will turn on and remain solid until the device turns off, another system is triggered, for example, dangerous motion, or when the user presses another button on the device, signifying that they understand what the light is telling them. The third light is a green LED that will blink three times when the ‘on’ button has been pressed to show the user that the device is on.

Controls

An active buzzer will be used for two functions. The first is another safety function that will be built in with the device. While the extraction and detection steps are running, the device must remain upright to prevent the microcentrifuge tubes from falling out of the device. If the device flips upside down or sideways, the active buzzer will be triggered and make a noise to alert the user. The buzzer noise will stop once the device has been placed back on the correct end. The buzzer will also sound for a few seconds when the device is turned on as an auditory signal to the user. A passive buzzer will sound after the extraction and detection steps are completed.

The device will have six buttons, each for different uses. One button will be a power button. One button will be an ‘off’ button to turn the device off. One button will begin the ten-minute extraction step. One button will begin the 30-minute detection step. One button will be for an emergency stop/restart/halt of the device if the user wants to stop testing for any reason. This will also shut down the PTC heating units to prepare the device for a full restart. The final button does not yet have a use. Each button will have a square covering to protect the internal wiring from potential damage.

The tilt ball switch will work with the active buzzer. If the device faces any direction that is not upright, it will trigger whatever step is occurring to stop immediately. A visual cue will tell the user what has occurred on the LCD1602, and the active buzzer will be an auditory cue. As said before, the device must always remain upright to ensure the liquid inside the microcentrifuge tubes is being heated correctly, the tubes do not fall out of their slots, and the device functions correctly.

Construction

Bo-FIND will be constructed with a DHT11 Temperature and Humidity Module. This will measure the temperature and humidity inside the device and trigger an emergency stop if either one reaches a dangerous level. We want to prevent any damage to the device's internals and keep the users as safe as possible at all times. We are using 2 PTC heating units: one for the extraction step and the other for the detection step.

Other parts that will be included in the device's construction are an 830 Tie-Points Breadboard, a UNO R3 Controller Board, Breadboard Jumper Wires, Female-to-Male Dupont Wires, and a USB Cable.

The device will have a cord with a USB end to power the Arduino. This end can be plugged into a vehicle or wall if used with a cord blockhead. After speaking to various farmers, we have learned that cow testing happens either in the field or in cow shoots. If farmers choose to test in the field, they will most likely have their vehicle with them for transportation. In this case, the Bo-FIND device will be plugged into a vehicle's USB port. If the farmers decide to do cattle testing using shoots, we predict they will take nasopharyngeal swabs of many cattle at a time and then do the testing altogether. This is where a blockhead would be used. A power source ensures the PTC heating units reach the required temperatures for proper DNA lysis and RPA function. We want to acknowledge Elegoo.com for providing us with much of the code and circuit diagrams used in the creation of our device parts.