Electroactive nanowells for spectrographic fluidic memory

Abstract

Current optical storage devices such as DVDs have their read/write capabilities fundamentally restricted by the diffraction limit of light. We present an optofluidic architecture for storing cocktails of colloidal quantum dots in electroactive nanowell structures. One application of these devices is the development of a fluidic memory approach which could enable the generation, reading and erasing of multiple bit information packages on single light diffraction limited data marks by spectral and intensity multiplexing of quantum dot cocktails. Here we focus on the development of the electroactive nanowell trapping architecture. Briefly, we have shown that by applying an electric potential between a top and bottom Indium Tin Oxide (ITO) electrodes, particles ranging from 5μm polystyrene spheres to 5nm quantum dots suspended in solution can be attracted, stored and rejected from a targeted well structure by electrokinetic actuation. Nanowells 100 nm in diameter and 1 μm deep were fabricated by depositing silicon and a small oxide thin film on top of an ITO cover slip, patterning the wells on electron beam resist followed by a series of dry etching steps that leave the ITO substrate exposed in the well sites. When the quantum dots are electrokinetically transported to their sensing sites, they are then excited by a UV-blue light, and their discrete fluorescent signal is captured by a fiber spectrometer. Data erasure can be selectively performed by reversing the polarity of the field and ejecting the quantum dots from the nanowell data marks.