Queen’s Genetically Engineered Machine (QGEM) is a design team focused on utilizing synthetic biology to solve real world problems involving medicine, sustainability, industry, and more. QGEM competes annually in the International Genetic Engineered Machine (iGEM) Giant Jamboree competition held in Boston, MA. To increase efficiency, QGEM asked APSC 103 students to design and build a compact, low-cost spectrophotometer that can quickly and reliably measure optical density. This device is to be used to estimate bacterial cell concentration.

Key metrics the students’ design must meet are (1) the ability to accommodate standard microcentrifuge tubes, (2) produce accurate readings compared to commercial models, (3) operate at appropriate wavelengths for bacterial samples, and (4) cost under $100.

The student group constructed a physical prototype of the spectrophotometer, as well as a CAD model to replicate the final design. They also developed code used for data conversion. The prototypes utilized materials such as Arduino microcontrollers, LEDs, and photodiodes. The students had the opportunity to tour the Discovery Lab, located in Botterell Hall, where they were able to see a commercial spectrophotometer in action.