CMOS Electrokinetic Systems and Fabrication Approaches for On-CMOS 3D Electrodes

Electrokinetics, including dielectrophoresis, electroosmosis and other phenomena, have become a popular technique for manipulating particles on the microscale using electric fields. Concurrently, CMOS microchips have become the dominant global technology. The combination of electrokinetics with CMOS appears ideal, as both utilise electric potentials, with the ability to make highly functional and scalable actuating systems. Since the first demonstration of electrokinetics implemented as part of a CMOS system in 2003, 49 further studies were published. But whilst the first study led to a commercialised product, those that followed have not achieved the same success. This review surveys the available literature on CMOS-based electrokinetic systems and highlight key trends in design. The obstacles blocking the field from greater success are explored and opportunities are identified, with future perspectives provided throughout. The review shows that, currently, the foremost limitation for CMOS-based electrokinetic systems lies with the front-end-namely, the electrode systems being employed. The need to extend beyond the planar configurations currently being used and fabricate 3D electrodes on-CMOS that can operate within high conductivity environments is put forward. This discussion then leads into a review on fabrication approaches for 3D electrodes with a specific focus on those compatible with a CMOS system.