Small machines are highly promising for future medicine and new materials. Recent advances in functional nanomaterials have driven the development of synthetic inorganic micromachines that are capable of efficient propulsion and complex operation. Miniaturization and large‐scale manufacturing of these tiny machines with true nanometer dimension are crucial for compatibility with subcellular components and molecular machines in operation. Here, block copolymer lithography is combined with atomic layer deposition for wafer‐scale fabrication of ultrasmall coaxial TiO2/Pt nanotubes as catalytic rocket engines with length below 150 nm and a tubular reactor size of only 20 nm, leading to the smallest man‐made rocket engine reported to date. The movement of the nanorockets is examined using dark‐field microscopy particle tracking and dynamic light scattering. The high catalytic activity of the Pt inner layer and the reaction confined within the extremely small nanoreactor enable highly efficient propulsion, achieving speeds over 35 µm s−1at a low Reynolds number of <10−5. The collective movements of these nanorockets are able to efficiently power the directional transport of significantly larger passive cargo.
Hydrocyclones are a simple and powerful particle separation technology, widely used in macroscale industrial processes, with enormous potential for miniaturization. Although recent efforts to shrink hydrocyclones to the centimeter scale have shown great promise for passive and high‐throughput microparticle separations, further miniaturization is constrained by limited understanding of the impact of device size scale and design on separation performance, and challenges in realizing the complex internal structures of hydrocyclones at small size scales using conventional microfabrication techniques. Here, fundamental scaling issues for hydrocyclones with sub‐millimeter critical dimensions are investigated, and the first microscale hydrocyclones with critical feature size as small as 250 µm are demonstrated by taking advantages of 3D printing using stereolithography coupled with digital light processing. The resulting devices are shown to provide high separation efficiency for particles as small as 3.7 µm while operating at high flow rates up to 40 mL min−1, with scaling analysis suggesting that sub‐micrometer particle separations can be achieved with further miniaturization, potentially making the technology suitable for the rapid isolation and concentration of both inorganic and biological nanoparticles.
more » « less- NSF-PAR ID:
- 10453413
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Materials Technologies
- Volume:
- 5
- Issue:
- 4
- ISSN:
- 2365-709X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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