The current trend for analytical systems and devices is to be small, portable, and low in cost because of the flexibility required to ensure their availability for on-site measurement applications. Using the concept of silicone optical technology (SOT), we propose a fully flexible analytical system, and digital fabrication of a compact optical module for flow-injection analysis (FIA) is demonstrated. A simple structure composed of a transparent polydimethylsiloxane (PDMS) optical core with a carbon black-dispersed PDMS cladding acts as a tiny but straightforward optical filter and shows an ability to trap light at tilted incidence; this structure is embedded on a silicone 3D-printed optical module via a simple injection and coating method. The coating properties, the optical trapping performance, and the cross talk test performance of the device were evaluated. The SOT-FIA optical module successfully demonstrated a 99.8% undesired light trapping performance; cross talk of less than 0.5% was observed, illustrating the low-noise detection performance of the SOT-FIA optical system. Colorimetric determination of iron in natural water samples demonstrated excellent linearity, a wide chemical analysis range, and good percentage recovery performance. The results of the determination in real water samples using the proposed SOT-FIA optical device agreed well with the results from the conventional spectrophotometric method. With advantages that include simplicity, low cost, flexibility, portability, and high sensitivity, the proposed optical device will be potentially useful for on-site chemical analysis measurements.
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