Abstract

The development of biosensors for the detection of biomolecules recognition is an extremely important problem in life science and clinical diagnostics. Many researchers and bio-scientists around the world are looking to present a simple and cost-effective ultra-sensitive platform for the bio-sensing applications in order to detect protein-protein interaction, DNA hybridization, and antigen-antibody interaction.

Microcantilever (MC) transducer is a well-known sensing mechanism for biosensing application. In this method, a surface-stress will be induced through the bimolecular recognition on the cantilever surface, which results in the MC deflection. The magnitude of deflection is related to the number of (or concentration of) biomolecules of interest that were immobilized on the MC's surface during the biosensing protocole. However, one of the main drawbacks of cantilever biosensors is the high amount of analytes (proteins, DNA, polypeptides, etc.) that are required for sensing experiments as the cantilever must be submerged in the analytes. In addition, the cantilever bending read-out system (that can be optical or electrical) has to be designed sensitive enough to make it possible to measure deflection in the range of a few nanometers.

In order to move toward ultra-sensitive biomolecular detection, one way is to increase the read-out resolution which makes the system more complex and expensive. Another solution is to fabricate the MC from materials different from silicon with less stiffness.

In addition, in order to reduce analytes consumption, integration of microfluidic systems with microcantilevers would be beneficial. Through this integration, both the volume of analytes and the time of response are reduced. This thesis reports a promising method towards ultra-sensitive biosensing by integration of microfluidic system into a polymeric microcantilever. The fabricated platform is referred as “Polymeric Suspended Microfluidics". In order to immobilize biomolecule of interest for the biosensing application inside the microfluidic system, gold nanoparticles (AuNPs) are integrated into the buried microfluidics by two different methods. The thesis also presents a novel 3D micromixer in order to implement in-situ synthesis of AuNPs. The 3D micromixer has been fabricated and tested for characterizing mixing performance.

The results of biosensing shows significant improvement in the sensitivity of the proposed platform compared with the common silicon based MC biosensor. The results show the proposed integrated sensing platform achieved a detection limit of 2ng/ml (100pM) toward the growth hormones biosensing (Ag-Ab interaction detection). The results demonstrate a proof-of-principal for successful polymeric cantilever fabrication towards the next generation of cantilever-based biosensing mechanism which has high potential to enable femtomolar (fM) biomolecular recognition detection.