# Microfluidic lab-on-chip design for efficient relative humidity sensing using a capacitive transducer

## TL;DR

This paper presents a low-cost microfluidic lab-on-chip sensor that uses a capacitive transducer to measure relative humidity with high precision and potential for energy harvesting.

## Contribution

The novel contribution is a microfluidic lab-on-chip design for humidity sensing with potential applications in biomedical and energy harvesting technologies.

## Key findings

- The system achieved a resolution of 33.993 mL/V and a sensitivity of 0.0596 V m/F.
- A prototype successfully charged a 22 pF capacitor, demonstrating potential for moisture-driven energy harvesting.
- The design shows promise for future sustainable mobile-device charging with further material and circuit improvements.

## Abstract

Recent advancements in microelectronics have provided substantial motivation for ongoing innovation within the domain of sensor and measurement technologies. The application of humidity sensors across diverse settings has been integral to system monitoring initiatives. There exists potential for further enhancements aimed at the development of sensors that are not only more efficient and safer but also more conducive to human interaction. The sensors thus developed and presented in this article hold promise for deployment in pioneering applications, offering precision measurements surpassing those of traditional sensors. Moreover, these advanced sensors are poised to be integral components of emergent applications in biomedical research and energy harvesting technologies. In this study, a lab-on-a-chip (LOC) design that uses microfluidic principles is designed and implemented. The proposed design is concerned with measuring the relative humidity of the surrounding medium using a capacitive transducer. The proposed methodology is designed, implemented, and tested on a low-cost experimental setup; results were recorded using LabVIEW. Achieving a resolution of 33.993 mL/V with a sensitivity of 0.0596 V m/F and noise tolerance of 2.028 V, the system successfully demonstrated its capability by implementing a prototype that charges a 22 pF capacitor. While the observed capacitance change and corresponding voltage output remain too low for direct device charging, this proof-of-concept demonstrates the potential of harvesting ambient moisture-driven energy. Further work on materials and circuit design will be needed to quantify power output and advance toward sustainable mobile-device charging.