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Quantum dots (QDs) are robust single photon emitters with a broad range of application in quantum information processing [1]. There is currently great interest in interacting QDs with nanophotonic structures such as photonic crystals for creating novel quantum devices [2]. For these applications it is essential that the QD with the correct spectral properties be placed in the high field region of the nanophotonic device [3]. A reliable technique for positioning individual QDs with desired properties at the correct location (e.g. a cavity mode) requires the ability to perform particle manipulation. Here we demonstrate a method to manipulate and immobilize preselected single colloidal QDs with nanometer precision by controlling the flow of the surrounding liquid via feedback.

We describe a technique for selective positioning and immobilization of individual colloidal CdSe/ZnS quantum dots (QDs) with nanometer accuracy along a two dimensional glass surface. The QDs are suspended in an aqueous solution, which is manipulated using electroosmotic flow (EOF) control. A water-immiscible resin is added to cause the QDs to separate into thin films along the channel surfaces, where they can still be manipulated. Additionally, crosslinking chemicals are introduced that locally polymerize the fluid when irradiated with UV light. These QDs are encapsulated with UV polymerization onto the surface at a desired location. We use this technique to assemble complex 3×3 arrays of pre-selected single QDs with 130 nm precision.

We present a method to individually position single QDs with nanometer precision by electroosmotic flow control (EOFC). Using EOFC, we demonstrate the ability to individually select a QD from anywhere within a 100 µm control area inside a microfluidic chamber and place it at a desired position to with a 52 nm precision. The single photon emission of EOFC manipulated QDs is verified by photon anti-bunching. These results demonstrate, for the first time, the ability to position single QDs to nanometer position accuracy in a microflu-idic environment. Such capability opens up the possibility for controllable placement of QDs in nanophotonic structures for the development of complex quantum devices, as well as in situ study of QDs for biological and sensing applications.