Integrated optical sensor in a digital microfluidic platform

The advent of digital microfluidic lab-on-a-chip (LoC) technology offers a platform for developing diagnostic applications with the advantages of portability, increased automation, low-power consumption, compatibility with mass manufacturing, and high throughput. However, most digital microfluidic platforms incorporate limited optical capabilities (e.g., optical transmission) for integrated sensing, because more complex optical functions are difficult to integrate into the digital microfluidic platform. This follows since the sensor must be compatible with the hydrophobic surfaces on which electrowetting liquid transport occurs. With the emergence of heterogeneous photonic component integration technologies such as those described herein, the opportunity for integrating advanced photonic components has expanded considerably. Many diagnostic applications could benefit from the integration of more advanced miniaturized optical sensing technologies, such as index of refraction sensors (surface plasmon resonance sensors, microresonator sensors, etc.). The advent of these heterogeneous integration technologies, that enable the integration of thin-film semiconductor devices onto arbitrary host substrates, enables more complex optical functions, and in particular, planar optical systems, to be integrated into microfluidic systems. This paper presents an integrated optical sensor based upon the heterogeneous integration of an InGaAs-based thin-film photodetector with a digital microfluidic system. This demonstration of the heterogeneous integration and operation of an active optical thin-film device with a digital microfluidic system is the first step toward the heterogeneous integration of entire planar optical sensing systems on this platform.