Optical tweezers assembly line for the micro-assembly of functional zeolite nanocontainer structures

Summary form only given. Zeolite L is a microporous crystalline material featuring high number of strictly aligned one-dimensional nano-channels across the whole crystal axis. These porous silicate are highly interesting as building blocks because, by entrapping different guest molecules within their nano-pores, they can bridge the gap between the molecular and the microscopic world [1]. In particular, if loaded with organic dyes, the confinement exerted by the pore dimensions can enhance some of the emissive properties of the molecular guest. In order to achieve specific photonic functionalities, these building blocks can be arranged and assembled in specific configurations.In our contribution, we present an approach complementary to the established assembly schemes by utilizing holographic optical tweezers [2] in a microfluidic environment. We demonstrate an optical tweezers assembly line (OTAL) which enables the construction of sophisticated microstructures with full control over each individual constituent [3]. The developed OTAL consists of a microfluidic Y-channel that define two laminar fluid flows. One of the flows ensures supply of the building blocks in non-sticking conditions so that they can easily be selected and optically trapped while the other flow enables the zeolite crystals to attach to each other and to the substrate by utilizing van-der-Waal interactions. We discuss exciting applications of the presented zeolite L structures, e.g. as microscopic polarization sensor, and comment on the high potential of the OTAL for further parallelization of the constructions process by automation of the optical trapping process or utilization of more than the demonstrated separated flow lines. Figure 1 shows an example of an optically assembled functional structure. Three zeolite L crystals loaded with a green/yellow fluorescent DXP dye are arranged and hold together with HOT. The geometrical constraints imposed by the nano-channels of the host crystal result - n a polarization-dependent fluorescence response of the aligned dye molecules. By means of linearly polarized fluorescence excitation, thus, the illumination pattern of the arranged building blocks can be selectively switched between different spatial states.