Engineering Success

To facilitate the in-field testing, we are engineering a portable unit to provide the BRD test results. Vets or farmers would take a deep nasopharyngeal swab of the cattle. Nasal swabs would be added to a tube with a prepared extraction buffer solution. This tube would then be heated to 100℃ for 10 minutes. The sample would then be transferred to the detection tubes. Each detection tube contains a different set of primers for pathogen detection. The RPA reaction will be allowed to start upon the addition of the prepared sample DNA mixture, then incubated at 37℃ for 30 minutes. Finally, the amplified DNA will be detected through a simple colour change due to hydroxynaphthol blue (HNB).

The first iteration of the device was one rectangular box design that had the extraction and detection steps occurring in close proximity. A 12V adaptor powered the heating element used for the detection and extraction steps, and a separate temperature controller was used to regulate heat appliances. Similar to the current device, there is one slot where a microcentrifuge tube will be placed for the extraction portion of the amplification. Next to this slot are five smaller slots for microcentrifuge tubes containing the primers required for RPA to occur. The fifth microcentrifuge tube is a control. We proposed a clear acrylic lining to enclose the device's elements. This decision was made solely because of the aesthetic properties of acrylic materials.

We revised the device's design after speaking to Amino Labs and participating in the 2024 TFC competition. Our second iteration is our minimal viable product using items obtained from Amazon. We worked with U of L tech services to drill holes in two aluminum blocks to create heating elements for the microcentrifuge tubes. Dr Chad Povey from the University of Lethbridge physics department helped with putting together the correct circuit for our first prototype. Our initial test was successful; the heating element did heat the aluminum holder. While our prototype does indeed achieve our goal of heating the tubes to the correct temperature, we wanted to make the design more streamlined and easy to use. It was quite heavy and bulky, so we worked on scaling down the current design. A Raspberry Pi was proposed to control the heating cycles needed for RPA to occur.

In our current iteration, we envision two separate heating elements enclosed in one rectangular block made of chitosan. Chitosan is an autoclavable, biodegradable polymer that can withstand temperatures up to 200℃. It is renewable and economically viable. Previously, we proposed an acrylic lining to shelter the device's components. After further discussion, we realized this would not work due to the low melting point of chitosan and its environmental dangers. The current device contains the same microcentrifuge placement as the first design, with the addition of an LCD 1602 screen and six buttons for various uses. An Arduino controls all the device's functions, unlike the previous design which used a temperature controller and a proposed Raspberry Pi. The heating elements/portions of the device are entirely separate from the rest of the internals. The heating blocks will now be insulated to prevent heat damage to other device parts. While the colour change of HNB can be easily observed with the naked eye, we anticipate creating a colour sensor that will be incorporated into our hand-held device. The sensor would have a colour detection threshold; when reached, it will send a message to the user’s phone.

Please contact us for our downloadable design! More information on the electronic components can be found on our hardware page.