Development of a Paper-Based Microfluidic Device for the Detection of Orthophosphate in Water

Brenno Ribeiro, University of Rhode Island


Phosphate is an essential nutrient for plant life in water that when in abundance can have a series of adverse effects on an ecosystem. As such it is of great interest to scientists and environmentalists alike to detect phosphate in the environment. The current state of detection technology leaves much to be desired however as devices are insensitive, ineffective, and sometimes expensive. This study presents a series of methods, systems, and devices that were developed in the pursuit of advancing the state of detection of orthophosphate in water. A lab-on-chip device was created utilizing the molybdenum blue reaction with a novel configuration that allows sensitive measurements to be taken without exposing the user to dangerous chemicals. The device houses the molybdenum complex in a bubble while the acid is spotted in a separate paper-based section. Button activation joins the two reagents and a colorimetric reaction is induced upon sample addition. The architecture was able to achieve a limit of detection in the parts per billion (ppb) range, a superior performance to currently available commercial devices. An accompanying light box was created so that colorimetric measurements could be taken in the field using a stable lighting environment. In addition, an iOS app was developed that could instantly and reliably quantify measurement concentrations based on obtained RGB values and programmed calibration curves. The app features a data architecture that connects to an online data center offering a highly scalable worldwide system for tracking and analyzing field measurements. An inexpensive infrared detection system was also developed with an infrared camera and Raspberry Pi to take advantage of the peak absorbance of the molybdenum blue reaction. The system was able to increase the limit of detection on a popular commercial device by a factor greater than 10, greatly improving its capacity and showing potential for commercial adaptation.

Subject Area

Fluid mechanics|Chemistry|Engineering

Recommended Citation

Brenno Ribeiro, "Development of a Paper-Based Microfluidic Device for the Detection of Orthophosphate in Water" (2019). Dissertations and Master's Theses (Campus Access). Paper AAI13814253.