Photolithographic bio-patterning of magnetic sensors for biomolecular recognition

In the last years, magnetoresistive biosensors arrays have drawn a great interest due to their high sensitivity and integrability in lab-on-chip platforms. In such devices, the selective functionalization of the sensor active area is a major issue, in order to achieve high sensitivity and quantification capability. Here, we present a straightforward photolithographic procedure to create patterns of bio-reactive polymer regions on the sensor's surface, with micrometric resolution. The effectiveness of the procedure in providing high specificity and improved sensor performance is demonstrated in the case of magnetoresistive biosensors based on magnetic tunneling junctions (MTJs). On-chip biomolecular recognition assays demonstrate an enhanced sensitivity in selectively functionalized sensors with respect to non-patterned sensors, eventually leading to a limit of detection below the pM range, without target pre-concentration or chemical amplification.