From Sophisticated Analysis to Colorimetric Determination: Smartphone Spectrometers and Colorimetry

Abstract

Smartphone-based spectrometer and colorimetry have been gaining relevance due to the widespread advances of devices with increasing computational power, their relatively low cost and portable designs with user-friendly interfaces, and their compatibility with data acquisition and processing for "lab-on-a-chip" systems. They find applications in interdisciplinary fields, including but not limited to medical science, water monitoring, agriculture, and chemical and biological sensing. However, spectrometer and colorimetry designs are challenging tasks in real-life scenarios as several distinctive issues influence the quantitative evaluation process, such as ambient light conditions and device independence. Several approaches have been proposed to overcome the aforementioned challenges and to enhance the performance of smartphone-based colorimetric analysis. This chapter aims at providing researchers with a state-of-the-art overview of smartphone-based spectrometer and colorimetry, which includes hardware designs with 3D printers and sensors and software designs with image processing algorithms and smartphone applications. In addition, assay preparation to mimic the real-life testing environments and performance metrics for quantitative evaluation of proposed designs are presented with the list of new and future trends in this field.

Turning Image Sensors into Position and Time Sensitive Quantitative Colorimetric Data Sources with the Aid of Novel Image Processing/Analysis Software

“…Colorimetric quantification and dynamic analysis of various properties of matter, including chemical properties such as pH value, can be done through image sensor arrays. Wise use of image sensors is necessary, as machine vision will allow advances in many different fields [ 12 , 13 , 14 , 15 , 16 , 17 , 18 ]. The image information can be used as inputs for machine learning, internet of things (IoT), and artificial intelligence (AI).…”

Development of a tablet PC-based portable device for colorimetric determination of assays including COVID-19 and other pathogenic microorganisms

“…To enable prototyping a POC colorimetric device, a batterypowered, wirelessly connected and ready to use computer with an integrated camera(s) such as a smart phone, notebook personal computer (PC) and/or tablet PC are excellent candidates from the computing and communication capability point of view. [13][14][15][16] Accuracy and repeatability of colorimetric colour sensing is strongly dependent on ambient light conditions and light source congurations relative to the assays in vials (cuvettes or test tubes) and camera specications. A stable and reliable light source including natural lighting and/or indoor lighting is strongly desired.…”

“…To reduce interference from ambient light and make colour sensing stable and reliable, the distance between sample(s) and camera must be xed. 15 These requirements make the use of smart phones for the POC applications less desirable. Notebook PCs come with an integrated camera on the display side, thus an external camera is required.…”

“…The colour of the captured images can be expressed into hue-saturation-value (HSV) coordinates. 15 However, the HSV coordinates use different ranges for each parameter and are inconvenient for comparing colorimetric characteristics. Hue is expressed in the range of 0-360 , while saturation and value (lightness or brightness) are expressed in 0-100%.…”

A Portable Smartphone-Based Platform with an Offline Image Processing Tool for Rapid Paper-Based Colorimetric Detection of Glucose in Artificial Saliva

“…The easiest way for quantification of a substance is to capture the visible color change using a camera and measure the color intensity using imaging software. Due to the latest advances in camera and sensor technologies, existing smartphones are nowadays fabricated with a low-power, high-performance processor and high resolution digital camera for image capturing even in dark conditions which lead them to be used in the quantitative analysis [10], [11]. Smartphone colorimeters are used in sample quantification based on color change with respect to concentration as in peroxide quantification [12] or with respect to time as in methylene blue degradation [13].…”