Design and optimization of a Lab-on-Chip for application in cardiac biomarkers detection

In recent years, many studies have focused on organic bioelectronics, an emerging technology that employs organic transistors for biosensing applications. Compared to their inorganic counterparts, organic transistors exhibit several advantages, such as biocompatibility, low cost, high sensitivity, flexible substrate compatibility, easy fabrication and low-temperature processability. A specific category of organic transistors, the subject of this thesis, is the organic electrochemical transistor (OECT). In this device, the channel is typically made of a conductive polymer, such as Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), in contact with an electrolyte in which the gate is immersed. OECTs act as a transducer and amplifier of an ionic signal into an electrical one, operating at low voltages and providing significant amplification; this characteristic makes them highly pertinent in biosensing applications, such as medicine and biology. The objective of this thesis is to fabricate and optimize a microfluidic platform which embeds both the OECT and the functionalized gate in the framework of the funded ’LIFEBLOOD’ project. This platform was designed to detect the increase of two cardiac biomarkers, cardiac troponin (cTnI) and C-reactive protein (CRP), aiming to attain infarction early detection. Furthermore, a microfluidic blood/plasma separator (BPS) was designed to extract the plasma that will be used for the detection measurements. The integration of the OECT and BPS enables the creation of a Lab-on-Chip, which is the final objective of LIFEBLOOD project. OECT microfluidics and BPS were obtained by a combination of stereolithography and replication processes (soft-lithography), while gates and OECTs were fabricated using photolithography and inkjet printing. A variety of techniques and ink formulations were tested to optimize the printing process for PEDOT:PSS (which is the conductive polymer selected). Subsequently, electrical characterizations were performed, which entailed the extraction of principal figures of merit and the analysis of the stability of the devices. At the end, the BPS demonstrated to allow deionized water flow and will be tested with blood. The fabricated OECTs showed a proper current modulation which is fundamental for final device sensitivity.