Abstract
An optoelectronic, integrated system-on-glass for on-chip detection of biomolecules is here presented. The system’s working principle is based on the interaction, detected by a hydrogenated amorphous silicon photosensor, between a monochromatic light travelling in a SU-8 polymer optical waveguide and the biological solution under analysis. Optical simulations of the waveguide coupling to the thin-film photodiode with a specific design were carried out. A prototype was fabricated and characterized showing waveguide optical losses of about 0.6 dB/cm, a photodiode shot noise current of about 2.5 fA/ and responsivity of 495 mA/W at 532 nm. An electro-optical coupling test was performed on the fabricated device to validate the system. As proof of concept, hemoglobin was studied as analyte for a demonstration scenario, involving optical simulations interpolated with experimental data. The calculated detection limit of the proposed system for hemoglobin concentration in aqueous solution is around 100 ppm, in line with colorimetric methods currently on the market. These results show the effectiveness of the proposed system in biological detection applications and encourage further developments in implementing these kinds of devices in the biomedical field.
Highlights
Over recent decades, biosensing systems have spread and evolved due to constant technology improvement [1,2]
Optical investigations of the analyte features based on monitoring its optical properties can be performed by small, compact biosensors or Lab-on-Chip (LOC) devices [8,9,10], assuring quick response time and reduced reagents’ consumption without sacrificing high performance in terms of sensitivity and reliability [11,12,13]
The results are plotted in Figure 3: the power absorption increases as SU-8 thickness decreases, and the indium-tin oxide (ITO) thin film acts as a buffer layer helping the coupling of light
Summary
Over recent decades, biosensing systems have spread and evolved due to constant technology improvement [1,2]. Optical investigations of the analyte features based on monitoring its optical properties (such as absorption, fluorescence, chemiluminescence or complex refractive index) can be performed by small, compact biosensors or Lab-on-Chip (LOC) devices [8,9,10], assuring quick response time and reduced reagents’ consumption without sacrificing high performance in terms of sensitivity and reliability [11,12,13] These microdevices can recognize a change in the complex refractive index of a biological sample, and relate it to the analyte concentration in a non-destructive inspection, without hazardous chemicals, avoiding the need for large sample volumes and for their subsequent disposal. The presented approach intends to simplify the existent systems without sacrificing sensing performance
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