Optical sensing for on-chip digital microfluidics

A digital microfluidic architecture is introduced for micron-scale localized fluid actuation and in in-situ optical sensing. Contemporary device integration challenges related to localization and device scalability are overcome through the introduction of a bi-layered digital microfluidic multiplexer. Trinary inputs are applied through differential combinations of voltage signals between upper (column) electrodes and lower (row) electrodes. The ultimate layout provides increased scalability for massively parallel microfluidic actuation applications with a minimal number of inputs. The on-chip sensing technique employed here incorporates a microlens in a folded-cavity arrangement (fabricated by a new voltagetuned polymer electro-dispensing technique). Such a geometry heightens the sensitivity between the optical probe and fluid refractive properties and allows the device to probe the refractive index of the internal fluid. This optical refractometry sensing technique is merged with the actuation capabilities of the digital microfluidic multiplexer on a single lab-on-a-chip device.