Lab-on-chip at “La Sapienza”: when thin and thick film technologies meet chemistry and biological applications

Abstract

In this paper, we present a compact lab-on-chip system (LOC) fabricated on a conventional microscope glass slide using thin-film and thick-film technologies at “La Sapienza” University of Rome by the integration of know-how of researchers from Department of Electronic Engineering, Department of Aerospace and Astronautics Eng., Department of Chemistry and Department of Plant Biology.It integrates a heating chamber, an electrowetting-based droplet handling system and hydrogenated amorphous silicon (a-Si:H) photosensor array for biomolecule detection. The heating chamber incorporates a thin metal film heater whose geometry has been optimized for uniform temperature distribution over a 1cm2 area. An a-Si:H p-i-n junction integrated with the heater and biased with a forward current acts as temperature monitoring, achieving a sensitivity -3.3 mV/K with a linear behavior in the investigated range. The droplet-handling unit, relying on the electrowetting method, is designed to move the sample from the heating chamber to the sensor array. The unit includes a set of metal pads beneath a layer of PDMS that provides both the electric insulation of the electrodes and the hydrophobic surface needed by the electrowetting technique. The detection unit has been applied to quantify Ochratoxin A (OTA) based on hydrogenated amorphous silicon (a-Si:H) sensors. 2 μl of acidified toluene containing OTA at different concentrations were spotted on the silica side of a High Performance Thin Layer Cromatography plate and aligned with a a-Si:H p-i-n photodiode deposited on the LOC. Results show a very good linearity between OTA concentration and the sensor photocurrent down  to 0.1ng, showing that the presented system has the potential for a low cost system suitable for the early detection of toxins.To extend the application of LOC to the analysis of real matrices the group are developing new chemical strategies, that are also presented in this paper.