Programming Semiconductor Nanowire Composition with Sub-100 nm Resolution via the Geode Process.

We demonstrate the vapor-liquid-solid growth of single-crystalline i-Si, i-Si/n-Si, and SixGe1-x/SiyGe1-y nanowires via the Geode process. By enabling nanowire growth on the large internal surface area of a microcapsule powder, the Geode process improves the scalability of semiconductor nanowire manufacturing while maintaining nanoscale programmability. Here, we show that heat and mass transport limitations introduced by the microcapsule wall are negligible, enabling the same degree of compositional control for nanowires grown inside microcapsules and on conventional flat substrates. Efficient heat and mass transport also minimize the structural variations of nanowires grown in microcapsules with different diameters and wall thicknesses. Nanowires containing at least 16 segments and segment lengths below 75 nm are demonstrated.

Process Principles for Large-Scale Nanomanufacturing.

Nanomanufacturing-the fabrication of macroscopic products from well-defined nanoscale building blocks-in a truly scalable and versatile manner is still far from our current reality. Here, we describe the barriers to large-scale nanomanufacturing and identify routes to overcome them. We argue for nanomanufacturing systems consisting of an iterative sequence of synthesis/assembly and separation/sorting unit operations, analogous to those used in chemicals manufacturing. In addition to performance and economic considerations, phenomena unique to the nanoscale must guide the design of each unit operation and the overall process flow. We identify and discuss four key nanomanufacturing process design needs: (a) appropriately selected process break points, (b) synthesis techniques appropriate for large-scale manufacturing,

An aptamer-functionalized chemomechanically modulated biomolecule catch-and-release system.

The efficient extraction of (bio)molecules from fluid mixtures is vital for applications ranging from target characterization in (bio)chemistry to environmental analysis and biomedical diagnostics. Inspired by biological processes that seamlessly synchronize the capture, transport and release of biomolecules, we designed a robust chemomechanical sorting system capable of the concerted catch and release of target biomolecules from a solution mixture. The hybrid system is composed of target-specific, reversible binding sites attached to microscopic fins embedded in a responsive hydrogel that moves the cargo between two chemically distinct environments. To demonstrate the utility of the system, we focus on the effective separation of thrombin by synchronizing the pH-dependent binding strength of a thrombin-specific aptamer with volume changes of the pH-responsive hydrogel in a biphasic microfluidic regime, and show a non-destructive separation that has a quantitative sorting efficiency, as well as the system's stability and amenability to multiple solution recycling.