New multi-channel colorimetric sensor using a mobile phone

A mobile breakthrough for water environment monitoring: a new multi-channel colorimetric sensor on a mobile phone platform

Credit: Frontiers of environmental science and engineering (2022). DOI: 10.1007/s11783-022-1590-z

Reliable colorimetric analysis technologies have been widely praised for their highly sensitive and selective responses to various contaminants in environmental monitoring. In principle, the chromogenic agent selectively reacts with the target in the water samples, and the colored product reflects the specific absorbance spectrum.

Based on the Lambert-Beer law, absorbance is proportional to the concentration of absorbent species, providing the basis for the qualitative and quantitative detection of contaminants in water samples. Observation by eye has the advantage of low cost, but the accuracy is unsatisfactory. The conventional photoelectronic detector, such as the spectrophotometer and a microplate reader, is expensive and therefore difficult to apply in remote or resource-constrained environments.

The application scenario of colorimetric analysis technologies has led to keen interest in the balance between accuracy and cost. Considering both accuracy and cost, the development of colorimetric analysis technologies on the commercial cellular platform is gaining significant attention in environmental monitoring due to low cost, high flexibility, ease of miniaturization, and widespread cellular ownership. .

In particular, the unique benefits of cell-based colorimetric technology are expected to greatly accelerate environmental and health-related analysis capabilities in remote or less developed countries and regions. However, most of the reported studies have focused on single-channel colorimetric detection, which has resulted in limited detection efficiency, especially in the face of complicated contaminants in water samples.

Research into cellphone-based multichannel detection systems has attracted increasing interest because the systems have the potential to simultaneously detect multiple targets in a single measurement, and the techniques involved for rapid evaluation of water samples are fast, robust, and inexpensive. .

To realize multi-channel sensing capability, a traditional technology route is to directly acquire colorimetric images from 96-well plates using a cell phone camera. In all cases, most of the strategies to improve the detection capability of the cell-based system relied on a monochromatic light source, lacking universality and flexibility towards different contaminants showing different absorption peaks.

In this work, researchers from Harbin Institute of Technology Tsinghua University and Chongqing University proposed a cellphone-based colorimetric multi-channel sensor for water environmental monitoring. An array of white LEDs was used as an incident light to illuminate a 96-well plate. To improve the sensitivity of the sensor, a delicate optical path system was created using a diffraction grating to split six white beams that transmit through the multiple colored samples.

The transmitted light from six wells was collected by six optical fibers and imaged by a cell phone camera after passing through a diffraction grating, which allows the cell phone CMOS camera to capture the diffracted light for image analysis. The image was captured by a custom designed mobile app for analysis using a specific algorithm, resulting in detection results that were displayed using the same app.

This study titled “A Cell-based Colorimetric Multichannel Sensor for Environmental Water Monitoring” is published in Frontiers of environmental science and engineering.

The compact sensor has been successfully tested for the simultaneous detection of various environmental contaminants with an absorption wavelength range of 400–700 nm, achieving high sensitivity, specificity and reliability. By introducing the diffraction grating to divide light, sensitivity was improved more than six times over a system that directly photographed transmitted light.

As a successful proof of concept, the sensor was used to simultaneously detect turbidity, orthophosphate, ammonia nitrogen and three heavy metals with high sensitivity. In addition, the high stability (RSD of 0.37%–1.60%) and excellent recoveries (95.5%–106.0%) demonstrated that the sensor can perform accurate sensing in real water matrices .

With the advantages of strong sensing performance, low cost, ease of use, good portability, and multi-index measurement, the miniature sensor has demonstrated field sensing capabilities in environmental monitoring, which can be extended to point-of-care diagnosis , to food safety control and early warning of risks, etc.

In particular, by introducing the biorecognition materials, such as enzymes, antibodies and functional nucleic acid, the sensor has the potential to be more intelligent to realize trace detection of organic substances. Furthermore, this technology can be expected to allow detection channels up to 96 on the premise of overcoming the limitation of the volume or numbers of the diffraction grating.

More information:
Yunpeng Xing et al, A Cell-based Colorimetric Multi-Channel Sensor for Water Environmental Monitoring, Frontiers of environmental science and engineering (2022). DOI: 10.1007/s11783-022-1590-z

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Quote: A Mobile Breakthrough for Monitoring the Aquatic Environment: New Multi-Channel Colorimetric Sensor Using a Mobile Phone (2023, Jan 17) Retrieved Jan 17, 2023 from -environment- colorimetric-multichannel.html

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