Optofluidic sensor system with Ge PIN photodetector for CMOS-compatible sensing

TL;DR

This paper introduces an optofluidic biosensor system combining a microfluidic chip with a Ge PIN photodetector, enabling sensitive refractive index detection suitable for large-scale fabrication and integration.

Contribution

It presents a CMOS-compatible optofluidic sensor system with an integrated active photodetector exposed to fluids, enhancing detection capabilities and scalability.

Findings

Successful detection of different refractive indices

Compatibility with large-scale fabrication processes

Potential for integration into advanced sensing platforms

Abstract

Vertical optofluidic biosensors based on refractive index sensing promise highest sensitivities at smallest area foot-print. Nevertheless, when it comes to large scale fabrication and application of such sensors, cheap and robust platforms for sample preparation and supply are needed - not to mention the expected ease of use in application. We present an optofluidic sensor system using a cyclic olefin copolymer microfluidic chip as carrier and feeding supply for a complementary metal-oxide-semiconductor-compatibly fabricated Ge PIN photodetector. Whereas typically only passive components of a sensor are located within the microfluidic channel, here the active device is directly exposed to the fluid, enabling top-illumination. The capability for detecting different refractive indices was verified by different fluids with subsequent recording of the optical responsivity. All components excel in their capability to be transferred to large scale fabrication and further integration of microfluidic and sensing systems. The photodetector itself is intended to serve as a platform for further sophisticated collinear sensing approaches.