Controllable Fabrication and Rectification of Bipolar Nanofluid Diodes in Funnel-Shaped Si3 N4 Nanopores.

Solid-state nanopores attract widespread interest, owning to outstanding robustness, extensive material availability, as well as capability for flexible manufacturing. Bioinspired solid-state nanopores further emerge as potential nanofluidic diodes for mimicking the rectification progress of unidirectional ionic transport in biological K+ channels. However, challenges that remain in rectification are over-reliance on complicated surface modifications and limited control accuracy in size and morphology. In this study, suspended Si3 N4 films of only 100 nm thickness are used as substrate and funnel-shaped nanopores are controllably etched on that with single-nanometer precision, by focused ion beam (FIB) equipped with a flexibly programmable ion dose at any position. A small diameter 7 nm nanopore can be accurately and efficiently fabricated in only 20 ms and verified by a self-designed mathematical model. Without additional modification, funnel-shaped Si3 N4 nanopores functioned as bipolar nanofluidic diodes achieve high rectification by simply filling each side with acidic and basic solution, respectively. Main factors are finely tuned experimentally and simulatively to enhance the controllability. Moreover, nanopore arrays are efficiently prepared to further improve rectification performance, which has great potential for high-throughput practical applications such as extended release of drugs, nanofluidic logic systems, and sensing for environmental monitoring and clinical diagnosis.

Optimization and Fabrication of MEMS suspended structures for nanoscale thermoelectric devices.

By eliminating the influence of the substrate on parasitic thermal resistance, MEMS suspended structures become one of the accurate nanoscale thermoelectric performance evaluation devices. However, the process of MEMS suspended thermoelectric devices is complex, and its multilayer suspended structure is easy to fracture due to large stress. As a result, optimizing the design of suspended structures is critical in order to reduce manufacturing complexity and increase yield. In this study, finite element simulation is used to investigate the impacts of varying structures and sizes on the stress of MEMS suspended devices. The maximum stress and average stress of silicon nanomaterials are lowered by 90.89% and 92.35%, respectively, by optimizing the structure and size of the beams and nanobelt. Moreover, MEMS suspended devices of various structures are successfully manufactured. It not only increases the yield to more than 70% but also decreases the impact of strain on thermoelectric performance and can be used to create suspended devices with integrated silicon microstrips.

Exploring microstructures of metal-doped oxides via simulated Raman spectrum.

Solid solution of metal-doped oxide has been widely used in material industry and catalysis process. Its performance is highly correlated with the distribution of doped ions. Due to the complex distribution of doped ions in solid solution and its variation with temperatures, to obtain the microstructures of metal-doped ions in solid solution remains a substantial challenge. Taken Ce1-xZrxO2 as a model, the global structure searching, structures proportion with temperature determined by Boltzmann distribution, and the weighted simulation Raman spectra were integrated to explore the microstructures of metal-doped solid solution oxides. It was further verified by application into rutile and anatase TiO2 mixture, indicating that the present method is feasible to deduce the microstructure of metal composite oxides. We anticipate that it provides a powerful solution to explore microstructures of solid solution and complex metal oxides.

Correction: Study on the controllability of the fabrication of single-crystal silicon nanopores/nanoslits with a fast-stop ionic current-monitored TSWE method.

[This corrects the article DOI: 10.1038/s41378-023-00532-0.].

Study on the controllability of the fabrication of single-crystal silicon nanopores/nanoslits with a fast-stop ionic current-monitored TSWE method.

The application of single-crystal silicon (SCS) nanopore structures in single-molecule-based analytical devices is an emerging approach for the separation and analysis of nanoparticles. The key challenge is to fabricate individual SCS nanopores with precise sizes in a controllable and reproducible way. This paper introduces a fast-stop ionic current-monitored three-step wet etching (TSWE) method for the controllable fabrication of SCS nanopores. Since the nanopore size has a quantitative relationship with the corresponding ionic current, it can be regulated by controlling the ionic current. Thanks to the precise current-monitored and self-stop system, an array of nanoslits with a feature size of only 3 nm was obtained, which is the smallest size ever reported using the TSWE method. Furthermore, by selecting different current jump ratios, individual nanopores of specific sizes were controllably prepared, and the smallest deviation from the theoretical value was 1.4 nm. DNA translocation measurement results revealed that the prepared SCS nanopores possessed the excellent potential to be applied in DNA sequencing.

Fabrication and Characterization of Black GaAs Nanoarrays via ICP Etching.

GaAs nanostructures have attracted more and more attention due to its excellent properties such as increasing photon absorption. The fabrication process on GaAs substrate was rarely reported, and most of the preparation processes are complex. Here, we report a black GaAs fabrication process using a simple inductively coupled plasma etching process, with no extra lithography process. The fabricated sample has a low reflectance value, close to zero. Besides, the black GaAs also displayed hydrophobic property, with a water contact angle of 125°. This kind of black GaAs etching process could be added to the fabrication workflow of photodetectors and solar cell devices to further improve their characteristics.

The Recent Progress of MEMS/NEMS Resonators.

MEMS/NEMS resonators are widely studied in biological detection, physical sensing, and quantum coupling. This paper reviews the latest research progress of MEMS/NEMS resonators with different structures. The resonance performance, new test method, and manufacturing process of single or double-clamped resonators, and their applications in mass sensing, micromechanical thermal analysis, quantum detection, and oscillators are introduced in detail. The material properties, resonance mode, and application in different fields such as gyroscope of the hemispherical structure, microdisk structure, drum resonator are reviewed. Furthermore, the working principles and sensing methods of the surface acoustic wave and bulk acoustic wave resonators and their new applications such as humidity sensing and fast spin control are discussed. The structure and resonance performance of tuning forks are summarized. This article aims to classify resonators according to different structures and summarize the working principles, resonance performance, and applications.

Thermoelectric Properties of Cu2Se Nano-Thin Film by Magnetron Sputtering.

Thermoelectric technology can achieve mutual conversion between thermoelectricity and has the unique advantages of quiet operation, zero emissions and long life, all of which can help overcome the energy crisis. However, the large-scale application of thermoelectric technology is limited by its lower thermoelectric performance factor (ZT). The thermoelectric performance factor is a function of the Seebeck coefficient, electrical conductivity, thermal conductivity and absolute temperature. Since these parameters are interdependent, increasing the ZT value has always been a challenge. Here, we report the growth of Cu2Se thin films with a thickness of around 100 nm by magnetron sputtering. XRD and TEM analysis shows that the film is low-temperature α-Cu2Se, XPS analysis shows that about 10% of the film's surface is oxidized, and the ratio of copper to selenium is 2.26:1. In the range of 300-400 K, the maximum conductivity of the film is 4.55 × 105 S m-1, which is the maximum value reached by the current Cu2Se film. The corresponding Seebeck coefficient is between 15 and 30 µV K-1, and the maximum ZT value is 0.073. This work systematically studies the characterization of thin films and the measurement of thermoelectric properties and lays the foundation for further research on nano-thin-film thermoelectrics.

Doping Effect on Cu2Se Thermoelectric Performance: A Review.

Cu2Se, owing to its intrinsic excellent thermoelectric (TE) performance emerging from the peculiar nature of "liquid-like" Cu+ ions, has been regarded as one of the most promising thermoelectric materials recently. However, the commercial use is still something far from reach unless effective approaches can be applied to further increase the figure of merit (ZT) of Cu2Se, and doping has shown wide development prospect. Until now, the highest ZT value of 2.62 has been achieved in Al doped samples, which is twice as much as the original pure Cu2Se. Herein, various doping elements from all main groups and some transitional groups that have been used as dopants in enhancing the TE performance of Cu2Se are summarized, and the mechanisms of TE performance enhancement are analyzed. In addition, points of great concern for further enhancing the TE performance of doped Cu2Se are proposed.

Recent Progress of Miniature MEMS Pressure Sensors.

Miniature Microelectromechanical Systems (MEMS) pressure sensors possess various merits, such as low power consumption, being lightweight, having a small volume, accurate measurement in a space-limited region, low cost, little influence on the objects being detected. Accurate blood pressure has been frequently required for medical diagnosis. Miniature pressure sensors could directly measure the blood pressure and fluctuation in blood vessels with an inner diameter from 200 to 1000 m. Glaucoma is a group of eye diseases usually resulting from abnormal intraocular pressure. The implantable pressure sensor for real-time inspection would keep the disease from worsening; meanwhile, these small devices could alleviate the discomfort of patients. In addition to medical applications, miniature pressure sensors have also been used in the aerospace, industrial, and consumer electronics fields. To clearly illustrate the "miniature size", this paper focuses on miniature pressure sensors with an overall size of less than 2 mm × 2 mm or a pressure sensitive diaphragm area of less than 1 mm × 1 mm. In this paper, firstly, the working principles of several types of pressure sensors are briefly introduced. Secondly, the miniaturization with the development of the semiconductor processing technology is discussed. Thirdly, the sizes, performances, manufacturing processes, structures, and materials of small pressure sensors used in the different fields are explained in detail, especially in the medical field. Fourthly, problems encountered in the miniaturization of miniature pressure sensors are analyzed and possible solutions proposed. Finally, the probable development directions of miniature pressure sensors in the future are discussed.

The Fabrication of Micro/Nano Structures by Laser Machining.

Micro/nano structures have unique optical, electrical, magnetic, and thermal properties. Studies on the preparation of micro/nano structures are of considerable research value and broad development prospects. Several micro/nano structure preparation techniques have already been developed, such as photolithography, electron beam lithography, focused ion beam techniques, nanoimprint techniques. However, the available geometries directly implemented by those means are limited to the 2D mode. Laser machining, a new technology for micro/nano structural preparation, has received great attention in recent years for its wide application to almost all types of materials through a scalable, one-step method, and its unique 3D processing capabilities, high manufacturing resolution and high designability. In addition, micro/nano structures prepared by laser machining have a wide range of applications in photonics, Surface plasma resonance, optoelectronics, biochemical sensing, micro/nanofluidics, photofluidics, biomedical, and associated fields. In this paper, updated achievements of laser-assisted fabrication of micro/nano structures are reviewed and summarized. It focuses on the researchers' findings, and analyzes materials, morphology, possible applications and laser machining of micro/nano structures in detail. Seven kinds of materials are generalized, including metal, organics or polymers, semiconductors, glass, oxides, carbon materials, and piezoelectric materials. In the end, further prospects to the future of laser machining are proposed.

N-(4-Chloro-phen-yl)-4-(2-oxocyclo-pent-yl)butyramide.

In the title compound, C(15)H(18)ClNO(2), the amide group is coplanar with the chloro-phenyl group, making a dihedral angle of 1.71 (12)°. The cyclo-penta-none ring adopts a twist conformation. A weak intra-molecular C-H⋯O hydrogen bond is observed. Mol-ecules are linked into cyclic centrosymmetric dimers by paired N-H⋯O hydrogen bonds.

Establisment of a novel pig model of pancreatoduodenal allotransplantation.

BACKGROUND: Pancreas transplantation is a valid therapy for patients with type 1 diabetes mellitus (IDDM). This study was undertaken to establish a stable pig model of whole pancreatoduodenal allotransplantation of physiologically coincidence for pancreas transplantation. METHODS: The IDDM pig model was made by resection of the pancreas from the recipient. The portal vein of the donor was end-to-side anastomosed to the anterior mesenteric vein (equal to the superior mesenteric vein) or the portal vein of the recipient. The far end of the celiac axis was anastomosed to each other. With end-to-side fashion, the duodenum of the donor was anastomosed to the jejunum of the recipient. RESULTS: In 16 transplantations, results were satisfactory. The anatomical results and immune function including the function of the pancreas were similar to those of human being. CONCLUSION: Of the pancreas of the pig, this study of pancreatic transplantation shows that the novel pig whole pancreatoduodenal allotransplantation model is ideal.

[Improvement of the model of pancreas-duodenal transplantation in swines].

OBJECTIVE: To improve the procedures of pancreas-duodenal transplantation in swines in order to establish a technically stable model that accords with the physiological situation. METHODS: The whole pancreatoduodenal graft was harvested with in situ flush using 4 degrees C preservation solution. Type 1 diabetes was induced surgically by total pancreatectomy. By end-to-side fashion, the segment of abdominal aorta containing the celiac artery and the anterior mesenteric artery (equal to superior mesenteric artery in human) was anastomosed to the abdominal aorta of recipient which is behind the renal artery, the portal vein was anastomosed to the anterior mesenteric vein of the recipient, the duodenum was anastomosed to the jejunum of the recipient. The graft was placed in the anterior right peritoneal cavity. RESULTS: A total of 28 swines were used as recipients. Of them, two died of anesthetic accident, another two died of hyperacute rejection 2 hours, 19 hours after operation respectively; the others underwent the operation uneventfully. Their survival time was 5-21 days, blood sugar was (11.33+/-1.66) mmol/L on the first day after operation, and (5.65+/-0.89) mmol/L on the third day. CONCLUSION: This kind of model is stable, and the operative method and procedures are relatively simple and practicable.

Lithium pipecolinate as a facile and efficient ligand for copper-catalyzed hydroxylation of aryl halides in water.

Direct hydroxylation of a wide scope of aryl halides was catalyzed by a combination of CuI and lithium pipecolinate in water with yields up to 92%.