Simple and Cost-Effective Fabrication of Embossed Colorimetric Sensor Array for an Optoelectronic Nose via...

An optoelectronic nose, which consists of a colorimetric sensor array (CSA) to generate a combined response against a target analyte and a hand-held reader to compare it with a preset molecular fingerprint library, has overcome the limitations of an electronic nose. However, it remains challenging to develop an optoelectronic nose-based instrument for multiple analyte identification in real-world applications due to the complex fabrication approach of the CSA. Aiming to address this challenge, we propose a simple approach for the fabrication of a disposable CSA via the integration of self-adhesive paper and porous colorimetric silica microparticles. Thirty-six sensor units were developed by loading sensitive dyes onto mesoporous silica microparticles and further embossing them on the self-adhesive paper in a 12 × 3 fashion using a 384-well plate. Thereafter, we examined the discriminative power of the embossed CSA against 12 chemical threat agents (CTAs) in the vapor phase within 5 min of exposure at two different concentrations below their immediately dangerous to life and health (IDLH) threshold. Different CTAs were identified below their IDLH levels using a support vector machine with 99% classification accuracy for qualitative analysis and 96% classification accuracy for semiquantitative analysis. The embossed CSA was found to be impervious to 100% RH, and the limit of detection was achieved below the permissible exposure level for the CTAs. This fabrication approach addresses key limitations of existing methods. It is facile, cost-effective, and reproducible (RSD < 9%). Its versatility in terms of the size, shape, and design of the CSA arrays, along with compatibility with a wide range of colorimetric particles, makes it well-suited for mass production and real-world applications.