Novel device concepts in nanoelectronics, optics and bio-sensing based on new materials in the form of micro- and nanoscale building blocks require new fabrication strategies. Structures cannot be carved out of a substrate by conventional top-down fabrication methods alone. New ways of heterogeneous bottom-up integration are required, especially when different micro- and nanoscale components have to be merged. The combination of traditional and novel top-down patterning processes with directed self-assembly is a promising approach that can exploit the best of both worlds. We use capillary forces of a moving meniscus to direct objects into desired positions on a topographically patterned template. Capillary forces are strong and very sensitive regarding the trap geometry. Thus, high-yield and highly specific positioning of small colloidal objects is possible, even with control of the orientation when shape-anisotropic particles, such as nanorods, are used. The method of capillary assembly is further advanced by replacing the colloidal drop sandwiched between the template and a cover slide by a dedicated microfluidic device that delivers the colloidal suspension from a slit onto the template. The microfluidic device improves control of the position and the size of the assembly area. In addition, it facilitates a continuous supply of particle suspension for large-area assemblies and enables control of the colloid composition as required for the fabrication of cross-gradients. The simultaneous assembly from two capillary bridges close to each other enables size-selective assemblies and controlled fabrication of particle clusters from different components in a single assembly run. Applications of the microfluidic assembly device and strategies for the transfer and harvesting of particle clusters produced in this way will be discussed.

Assembly and integration of heterogeneous micro- and nano-scale building blocks from a microfluidic device

248th National Meeting (2014)

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