The continuous energy-harvesting in moisture environment is attractive for the development of clean energy source. Controlling the transport of ionized mobile charge in intelligent nanoporous membrane systems is a promising strategy to develop the moisture-enabled electric generator. However, existing designs still suffer from low output power density. Moreover, these devices can only produce short-term (mostly a few seconds or a few hours, rarely for a few days) voltage and current output in the ambient environment. Here, we show an ionic diode–type hybrid membrane capable of continuously generating energy in the ambient environment. The built-in electric field of the nanofluidic diode-type PN junction helps the selective ions separation and the steady-state one-way ion charge transfer. This directional ion migration is further converted to electron transportation at the surface of electrodes via oxidation-reduction reaction and charge adsorption, thus resulting in a continuous voltage and current with high energy conversion efficiency.

Wet chemical etching is essential not only for processing silicon (Si) wafers but also for forming diverse structures, significantly promoting the development of the semiconductor industry. However, tight control of etched topography at the nanoscale and even atom-scale in a controllable and reproducible fashion can be hardly achieved in either laboratory research or industrial production, seriously hindering further enhancement of high-performance Si-based electronic devices. Herein, the roles of mechanically driven defects in wet etching were systematically investigated toward promoting controllable wet etching of monocrystalline Si. The role of antietching of mechanically driven amorphous Si (a-Si) and the role of promoting etching of distorted Si (including dislocations and stacking faults) were revealed in anisotropic or isotropic etchants. It was also found that the nucleation of nanocrystals in the a-Si area with increasing contact pressure can lead to deactivation of the antietching mask, and the required contact pressure for deactivation in KOH and tetramethyl ammonium hydroxide solutions was much higher than that in HF/HNO3 mixtures. The selective etching mechanisms for every defect including a-Si, distorted Si, and nanocrystals were further addressed down to the atom-scale based on the proposed dissolution model. This study provides insights into deeply understanding the role of defects in wet etching and pushes forward the idea of controllable wet chemical etching in the Si-based semiconductor industry.

Surface-enhanced Raman spectroscopy (SERS) substrate-based microfluidic systems are applied extensively in diverse fields. For affordable detection and diagnosis, we propose a novel strategy for flexible, low-cost, and rapid fabrication of microfluidic SERS substrates by metal-assisted chemical etching of scratches on a silicon surface. A silicon substrate was spin-coated with polyketone resin (PK), and patterned by scratching with a diamond tip. Notably, defects created by diamond tip scratching on silicon substrate promoted subsequent metal deposition. A micro/nano nested structure was prepared by metal-assisted chemical etching process based on combined effect of scratching and metal catalysis. The PK layer served as a stable mask during metal deposition and etching. The prepared SERS-active detection sites with micro/nano nested structures exhibited substantial enhancement effects and good stability. Taking rhodamine 6G as a probe molecule, the microfluidic SERS substrate exhibited a high detection capability, with nanomolar detection limits (10-9 M) and high long-term stability (at least 120 days). The micro/nano nested structure exhibited an enhancement factor of 2.725 × 105 compared to a gold film deposited on a flat silicon surface. The proposed method is promising for chemical and biological detection applications.

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Metallic micro/nanostructures present a wide range of applications due to the small size and superior performances. In order to obtain high-performance devices, it is of great importance to develop new methods for preparing metallic micro/nanostructures with high quality, low cost, and precise position. It is found that metallic micro/nanostructures can be obtained by scratch-induced directional deposition of metals on silicon surface, where the mask plays a key role in the process. This study is focused on the preparation of keto-aldehyde resin masks and their effects on the formation of scratch-induced gold (Au) micro/nanostructures. It is also found that the keto-aldehyde resin with a certain thickness can act as a satisfactory mask for high-quality Au deposition, and the scratches produced under lower normal load and less scratching cycles are more conducive to the formation of compact Au structures. According to the proposed method, two-dimensional Au structures can be prepared on the designed scratching traces, providing a feasible path for fabricating high-quality metal-based sensors.