On-chip detection performed by amorphous silicon balanced photosensor for lab-on chip application

Plug and measure - a chip-to-world interface for photonic lab-on-a-chip applications

The integration of detection mechanisms with microfluidics may be one of the most promising routes towards widespread application of Lab-on-a-Chip (LoC) devices. Photonic detection methods like in the so-called Photonic Lab-on-a-Chip (PhLoC) have advantages such as being non-invasive, easy to sterilize and highly sensitive even with short integration times and thus allow in situ monitoring and quantification of biological and chemical processes. The readout of such detection methods usually requires special training of potential users, as in most cases they are confronted with the need of establishing fiber-optics connections to and from the PhLoC and/or rely on the use of complex laboratory equipment. Here, we present a low-cost and robust chip-to-world interface (CWI), fabricated by CO2-laser machining, facilitating the non-expert use of PhLoCs. Fiber-optics with standard SMA-connectors (non-pigtailed) and PhLoCs can be plugged into the CWI without the need for further adjustments. This standardization bestows great versatility on the interface, providing a direct link between PhLoCs and a wide range of light sources and photo-detectors. The ease-of-use of the proposed simple plug mechanism represents a step forward in terms of user-friendliness and may lead PhLoC devices to practical applications.

Thin Film Differential Photosensor for Reduction of Temperature Effects in Lab-on-Chip Applications

This paper presents a thin film structure suitable for low-level radiation measurements in lab-on-chip systems that are subject to thermal treatments of the analyte and/or to large temperature variations. The device is the series connection of two amorphous silicon/amorphous silicon carbide heterojunctions designed to perform differential current measurements. The two diodes experience the same temperature, while only one is exposed to the incident radiation. Under these conditions, temperature and light are the common and differential mode signals, respectively. A proper electrical connection reads the differential current of the two diodes (ideally the photocurrent) as the output signal. The experimental characterization shows the benefits of the differential structure in minimizing the temperature effects with respect to a single diode operation. In particular, when the temperature varies from 23 to 50 °C, the proposed device shows a common mode rejection ratio up to 24 dB and reduces of a factor of three the error in detecting very low-intensity light signals.