ECE Senior Capstone Project 2020 Tech Notes

Wearble Pollution PatchBy Diego Espinoza Rodriguez, ECE ‘20_____________________________________________________

Introduction This project aims to create a portable andinexpensive chemical detector using cotton threadsdyed with special pigments. These pigments performa core function in this project due to their ability tochange color when exposed to hazardous chemicals.This colorimetric property is important to studybecause the ability to distinguish and characterizethose color changes allows for the identification ofchemicals. This paper will cover the need forchemical detection, current chemical detectors, andthen it will examine the pigments we utilized.

The Need Chemical detection is important in industrialfactories, rural and local farmland, urban cities, andmore. There are many industries where precise andaccurate chemical detection systems can help savelives and prevent injuries. For example, in thedangerous working environment of a mine,hazardous gasses can fill the mine shafts during themining process. Early detection of such gasses canlead to a more successful evacuation and a propermitigation. Another example is in farmland whererunoff and other waste waters that are too toxic canharm animal life, increase erosion, and harm humanlife. Detection of dissolved chemicals can helpfarmers to adjust their use of fertilizers to minimizethese negative effects. Modern chemical detection methods are able tomeet the needs of many industrial factories but theircomplexity and high cost can make theninaccessible to low income communities and farms.

For example, water quality testing requires plethoraof testing chemicals, equipment and procedures. Airmonitoring systems can be extremely costly and notportable.

Previous Work This project is not the first to use such dyes todetect various chemicals. (Lim, Feng, Kemling,Musto, & Suslick, 2009) describes a method inwhich an array of color changing pigments isarranged on paper. Various forms of electronic“nose” sensors have been implemented on paperwith differing sensor reading equipment. We will base our project on technologydeveloped in Owyeung, Panzer, & Sonkusale,(2019), which describes a method for the dyeing andtreatment of cotton threads for use as sensors. The detection of hazardous chemicals can be donethrough the use of several types of dyes. Commonlyused ones include Bronsted acidic or basic dyes,Lewis acidic or basic dyes, redox responsive dyes,or dyes with large permanent dipoles includingsolvatochromic or zwitterionic dyes (Owyeung, etal, 2019).

The Dyes UsedBromothymol BlueBTB, for short, is a common pH indicator that isused to measure substances that are close to aneutral pH. The colors range from a light yellow at apH of 6.0 to blue at a pH of 7.6. It can also turnmagenta in a highly acidic solution.

.

Gold

Figure 1. A sample of the cotton threads in the dyeingprocess.

Bromocresol PurpleBromocresol purple is a dye in the triphenylmethane family and a pH indicator. It is colored yellow belowpH 5.2, and violet above pH 6.8. It absorbs light wellat 419 nanometers.

Neutral redNeutral red is eurhodin dye. It is commonly used asa stain in biological applications. It color range goesfrom red to yellow between a pH of 6.8 to 8.0,respectively.

Nile RedNile red a commonly used stain used to identifylipids. Data on its pH range was not found. However,it was found to have some fluorescent properties innon polar solutions.

Phenol RedPhenol red is an indicator dye that changes colorfrom yellow to red in the pH range 6.8 to 8.2. Above8.2 it is a fuchsia color. It’s structure is similar toBTB and bromocresol purple. It can serve as anindicator for cell cultures, and as a test homeswimming pools.

Methyl RedMethyl red is an indicator azo dye. It can measurepH ranges from 4.4 to 6.2, and it changes from red toyellow, respectively. It has uses in microbiology andit has some fluorescent properties.

Brilliant YellowBrilliant yellow is a commonly used azo dye and pHindicator. It was a color range from yellow at pH of 6.5 to red-orange at 8.0. It has uses as a biosensor, ananti-fungal agent, and an anti-AIDS agent. It has apeak light absorption at 497 nm.

ConclusionThe information presented about the various dyes isincomplete in how it can be directly used for ourproject. In order to characterize the color changes, weneed to run several strict tests with solutions of adesired pH in order to take images of each dye and itscolor range. We would then need to extract the colordata as RBG values in order to finish theimplementation of the project. This information willserve as a general guideline about how to test andcalibrate the project

References1. Lim, S. H., Feng, L., Kemling, J. W., Musto, C. J., & Suslick, K. S. (2009). An optoelectronic nose for the detection of toxic gases. Nature chemistry, 1(7), 562–567. https://doi.org/10.1038/nchem.360

2. Owyeung, R.E., Panzer, M.J. & Sonkusale, S.R. (2019). Colorimetric Gas Sensing Washable Threads for Smart Textiles. Sci Rep 9, 5607. https://doi.org/10.1038/s41598-019-42054-8

3. All chemical dye information obtained from www.sigmaaldrich.com