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Defying the isotropic nature of traditional chemical etch, metal-assisted chemical etching (MacEtch) has allowed spatially defined anisotropic etching by using patterned metal catalyst films to locally enhance the etch rate of various semiconductors. Significant progress has been made on achieving unprecedented aspect ratio nanostructures using this facile approach, mostly in solution. However, the path to manufacturing scalability remains challenging because of the difficulties in controlling etch morphology (e.g., porosity and aggregation) and etch rate uniformity over a large area. Here, we report the first programmable vapor-phase MacEtch (VP-MacEtch) approach, with independent control of the etchant flow rates, injection and pulse time, and chamber pressure. In addition, another degree of freedom, light irradiation is integrated to allow photo-enhanced VP-MacEtch. Various silicon nanostructures are demonstrated with each of these parameters systematically varied synchronously or asynchronously, positioning MacEtch as a manufacturing technique for versatile arrays of three-dimensional silicon nanostructures. This work represents a critical step or a major milestone in the development of silicon MacEtch technology and also establishes the foundation for VP-MacEtch of compound semiconductors and related heterojunctions, for lasting impact on damage-free 3D electronic, photonic, quantum, and biomedical devices. 

Abstract On-chip manipulation of charged particles using electrophoresis or electroosmosis is widely used for many applications, including optofluidic sensing, bioanalysis and macromolecular data storage. We hereby demonstrate a technique for the capture, localization, and release of charged particles and DNA molecules in an aqueous solution using tubular structures enabled by a strain-induced self-rolled-up nanomembrane (S-RuM) platform. Cuffed-in 3D electrodes that are embedded in cylindrical S-RuM structures and biased by a constant DC voltage are used to provide a uniform electrical field inside the microtubular devices. Efficient charged-particle manipulation is achieved at a bias voltage of <2–4 V, which is ~3 orders of magnitude lower than the required potential in traditional DC electrophoretic devices. Furthermore, Poisson–Boltzmann multiphysics simulation validates the feasibility and advantage of our microtubular charge manipulation devices over planar and other 3D variations of microfluidic devices. This work lays the foundation for on-chip DNA manipulation for data storage applications.