A miniaturized all-in-one optical nose based on 3D printing technology and patterned paper substrate for discrimination of volatile organic compounds

Herein, an integrated design of a paper-based colorimetric sensor array, which includes both sensor array and sampling vessel is described. The paper substrate was patterned for providing hydrophobic barriers to deposit sensing elements, while a hydrophilic regions were embedded on the paper for sample solution. In this way, the paper substrate works as a sensing device and sampling vessel, simultaneously. A miniaturized cubic reaction chamber sizing (30 × 30 × 0.02) mm, equipped with a small aperture for sample injection was fabricated using 3D printing technology to hold the paper substrate. The required sample volume was lowered down dramatically (13.0 μL) due to the all-in-one sampling and sensing device. This miniaturized sensor array concept was employed to detect and discriminate volatile organic compounds (VOCs) relating to different solvent families that are known as cancer biomarkers. A colorimetric sensor array was fabricated by spotting 12 indicators belonging to three families of solvatochromic dyes, pH indicators and metallochromic dyes. This simple proposed device was able to discriminate the studied solvents into three chemical families including polar protic, dipolar aprotic and nonpolar with 93% accuracy. In addition, this sensor showed potential for quantitative and semi-quantitative analysis of volatile compounds in their mixtures. In total, the designed device is portable, rapid, and cost-effective and requires low volumes of samples that can be considered a good candidate for various VOC analysis with limited volume.