A Microdroplet-Based Colorimetric Sensing Platform on a CMOS Imager Chip.
Kyle R Mallires1,2, Di Wang2, Peter Wiktor2
1School for Engineering of Matter, Transport & Energy, Arizona State University, Tempe, Arizona 85287, United States.
Analytical Chemistry
|June 6, 2020
Summary
Researchers developed a novel single-chip chemical sensor by printing colorimetric microdroplets onto CMOS imagers. This approach enables sensitive, reusable, and easily calibrated mobile sensing for applications like ammonia detection.
Area of Science:
- Optoelectronics
- Chemical Sensing
- Materials Science
Background:
- Mobile chemical sensors face challenges in integration, calibration, and cost.
- CMOS imagers offer a low-cost, miniaturized platform for optoelectronic sensing.
- Integrating sensing elements directly onto imagers can simplify device architecture.
Purpose of the Study:
- To develop a single-chip mobile chemical sensing platform.
- To demonstrate the feasibility of printing colorimetric sensors onto CMOS imagers.
- To assess the performance of the integrated sensor for detecting gaseous ammonia.
Main Methods:
- Printing colorimetric microdroplets composed of a nonvolatile solvent onto a CMOS photodiode array.
- Using the CMOS imager to optically detect color changes in the microdroplets.
- Quantifying gaseous ammonia using a copper(II)-based colorimetric formulation.
Main Results:
- Achieved limits of detection for ammonia as low as 27 ppb.
- Demonstrated low sensor-to-sensor variation (<10%) across multiple printed arrays.
- Showcased sensor reusability, good selectivity, and tunable sensitivity via droplet size control.
Conclusions:
- Direct printing of colorimetric sensors onto CMOS imagers enables highly sensitive and repeatable mobile chemical detection.
- This single-chip approach simplifies sensor integration and calibration for commercial devices.
- The technique is generalizable to various colorimetric formulations and analytes.
