Senior Design Team sdmay25-17 • MicroBial-Electronic Pill Sensor SD Site

Project Overview

Excessive nitrate concentration in bodies of water, often a result of agricultural runoff, poses significant environmental hazards, endangering both aquatic life and the lives of those consuming the water. Current methodologies for identifying nitrate concentration in agricultural runoff are intensive, expensive, and inefficient, requiring manual sampling and off-site analysis. By providing more efficient, cost-effective, and autonomous nitrate detection, the microbial pill sensor provides continuous monitoring of nitrate concentrations for both environmentalists and farmers. The microbial pill sensor will enable environmentalists and farmers to make more informed decisions regarding the health of waterbodies and fertilization processes.

The microbial pill sensor uses a novel biosensing detection mechanism, relying on bioengineered microbes to identify the presence of nitrate in the environment. The microbes used by the microbial pill sensor have been genetically engineered to express green-fluorescent protein (GFP) due to the presence of nitrate. The concentration of nitrate in the environment can be determined through the fluorescent response of the expressed GFP.

The microbial pill sensor is a 5 x 5 x 10 mm3 capsule broken into distinct modules. The bioengineered microbes are contained within a housing chamber, and the solution flows in through a selective membrane located at the top of the capsule. The electronic components are situated directly below the housing chamber and arranged in three distinct optical detection, microcontroller, and temperature control PCB layouts. A 488 nm wavelength LED is required to excite the expressed GFP, resulting in the emission of 532 nm wavelength light. The emitted light is captured by a photodetector, resulting in a photocurrent proportional to the presence of nitrate in the environment. A microcontroller is responsible for the activation of the LED at the desired interval and the transmission of the photocurrent value to an external device via low-power Bluetooth. An external GUI application processes the measurement and displays recorded nitrate concentrations for evaluation by the user. Additional temperature control is required to maintain the viability of microbes within the housing chamber.

The modular design of the microbial pill sensor enables the development of individual modules simultaneously, with each member assigned a particular module. Potential LED and photodetector components have been obtained, and the ESP32-C3 microcontroller has been selected for the MCU component. PCB design of the optical detection and microcontroller modules is currently underway via Ki-CAD and an initial design of the external capsule has been generated via Fusion 360.

A breadboard prototype has been produced, integrating an ESP32-C3 dev kit, RGB LED, and photodetector to provide a proof of concept for the microbial pill sensor design. External data transmission via low-power Bluetooth on the ESP32-C3 has been achieved, and the recorded data is viewable on the first iteration of the external GUI application. The next steps consist of finalizing the PCB design, testing the fabricated PCB modules, and integrating them into the external capsule. Functional testing will be conducted with fluorescent beads to reproduce the functionality of the bio-engineered microbes.

Weekly Reports

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Lightning Talks

Lightning Talk 1: Product Research
Lightning Talk 2: Problem and Users
Lightning Talk 3: User Needs and Requirements
Lightning Talk 4: Project Planning
Lightning Talk 5: Detailed Design
Lightning Talk 6: Design Check-In
Lightning Talk 7: Prototyping
Lightning Talk 8: Ethics and Professional Responsibility

Design Documents

491 Final Design Document