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Small RNA molecules have an important role in gene regulation and RNA silencing therapy, but it is challenging to detect these molecules without the use of time-consuming radioactive labelling assays or error-prone amplification methods. Here, we present a platform for the rapid electronic detection of probe-hybridized microRNAs from cellular RNA. In this platform, a target microRNA is first hybridized to a probe. This probe:microRNA duplex is then enriched through binding to the viral protein p19. Finally, the abundance of the duplex is quantified using a nanopore. Reducing the thickness of the membrane containing the nanopore to 6 nm leads to increased signal amplitudes from biomolecules, and reducing the diameter of the nanopore to 3 nm allows the detection and discrimination of small nucleic acids based on differences in their physical dimensions. We demonstrate the potential of this approach by detecting picogram levels of a liver-specific miRNA from rat liver RNA. Synthetic nanopores can count individual microRNA molecules that have been isolated from cellular RNA with a protein-based enrichment method.

Devices in which the transport and storage of single electrons are systematically controlled could lead to a new generation of nanoscale devices and sensors 1 , 2 , 3 . The attractive features of these devices include operation at extremely low power, scalability to the sub-nanometre regime and extremely high charge sensitivity 4 , 5 , 6 , 7 , 8 , 9 . However, the fabrication of single-electron devices requires nanoscale geometrical control, which has limited their fabrication to small numbers of devices at a time 9 , 10 , 11 , 12 , 13 , 14 , 15 , significantly restricting their implementation in practical devices. Here we report the parallel fabrication of single-electron devices, which results in multiple, individually addressable, single-electron devices that operate at room temperature. This was made possible using CMOS fabrication technology and implementing self-alignment of the source and drain electrodes, which are vertically separated by thin dielectric films. We demonstrate clear Coulomb staircase/blockade and Coulomb oscillations at room temperature and also at low temperatures. Single-electron devices offer many advantages over traditional devices, but it is a challenge to fabricate them in large numbers. A novel geometry in which the source and drain electrodes are vertically separated by thin dielectric films, and nanoparticles attached to the sidewall of the dielectric films act as Coulomb islands, can now be used for the CMOS-compatible fabrication of single-electron devices that operate at room temperature.

Metasurface-based holograms, or metaholograms, offer unique advantages including enhanced imaging quality, expanded field of view, compact system size, and broad operational bandwidth. Multi-channel metaholograms, capable of switching between multiple projected images based on the properties of illuminating light such as state of polarization and angle of incidence, have emerged as a promising solution for realizing switchable and dynamic holographic displays. Yet, existing designs typically grapple with challenges such as limited multiplexing channels and unwanted crosstalk, which severely constrain their practical use. Here, we present a new type of waveguide-based multi-channel metaholograms, which support six independent and fully crosstalk-free holographic display channels, simultaneously multiplexed by the spin and angle of guided incident light within the glass waveguide. We employ a k -space translation strategy that allows each of the six distinct target images to be selectively translated from evanescent-wave region to the center of propagation-wave region and projected into free space without crosstalk, when the metahologram is under illumination of a guided light with specific spin and azimuthal angle. In addition, by tailoring the encoded target images, we implement a three-channel polarization-independent metahologram and a two-channel full-color (RGB) metahologram. Moreover, the number of multiplexing channels can be further increased by expanding the k -space’s central-period region or combing the k -space translation strategy with other multiplexing techniques such as orbital angular momentum multiplexing. Our work provides a novel approach towards realization of high-performance and compact holographic optical elements with substantial information capacity, opening avenues for applications in AR/VR displays, image encryption, and information storage.

Fermi-Dirac electron thermal excitation is an intrinsic phenomenon that limits functionality of various electron systems. Efforts to manipulate electron thermal excitation have been successful when the entire system is cooled to cryogenic temperatures, typically <1 K. Here we show that electron thermal excitation can be effectively suppressed at room temperature, and energy-suppressed electrons, whose energy distribution corresponds to an effective electron temperature of ~45 K, can be transported throughout device components without external cooling. This is accomplished using a discrete level of a quantum well, which filters out thermally excited electrons and permits only energy-suppressed electrons to participate in electron transport. The quantum well (~2 nm of Cr 2 O 3 ) is formed between source (Cr) and tunnelling barrier (SiO 2 ) in a double-barrier-tunnelling-junction structure having a quantum dot as the central island. Cold electron transport is detected from extremely narrow differential conductance peaks in electron tunnelling through CdSe quantum dots, with full widths at half maximum of only ~15 mV at room temperature. Electrons can behave as if they are at a temperature different from that of the solid in which they are embedded. Here, the authors demonstrate a room temperature device that can generate electrons with an effective temperature of 45 K by using quantum wells to filter out energetic particles.

We present a growth process mediated by nanoimprinted nanostructures specifically for producing bismuth selenide (Bi 2 Se 3 ) topological insulator nanoribbons with a high yield. In this process, topological insulator nanostructures are grown on nanoimprinted gratings by using a nanoparticle-catalyzed vapor–liquid–solid mechanism. In comparison with the growth processes performed on flat and randomly rough substrates, such a nanograting-mediated growth method produces topological insulator nanoribbons with a higher yield (∼15 000 nanoribbons/mm 2 ), a narrower average ribbon width ( w avg <60 nm), and a higher uniformity in ribbon width ( σ <30 nm); effectively suppresses the formation of other unwanted morphologies; and also results in the axial growth of nanoribbons along specific in-plane directions relative to pre-structured gratings. Such technical merits of nanograting-mediated growth are attributed to the preferential nucleation of Bi 2 Se 3 crystal seeds and the concomitant pinning of catalytic nanoparticles at ordered grating edges. Finally, Aharonov–Bohm interference oscillations in the magnetoresistance were observed and demonstrated the coherent transport of electrons through topological surface states of Bi 2 Se 3 nanoribbons. This growth process in combination with large-area nanoimprint lithography could serve as an important foundation for nanomanufacturing topological insulator nanoribbons with controllable feature size, large-area uniformity, and ordering, suitable for applications in future low-dissipation nanoelectronics.

Single-electron devices, in which the transport and storage of individual electrons is precisely controlled, have many potential benefits in the field of electronics, optics, and sensors. Fabrication of these devices requires the arrangement of device components (Coulomb island, source, drain, and gate electrodes) with nanometer scale precision. Although several methods have successfully demonstrated single-electron behavior, large-scale fabrication of single-electron devices has not been possible. This research aims to - (1) Come up with a method which would allow the fabrication of single-electron devices on a large scale, (2) Make the fabrication method compatible with current CMOS technology, and, (3) Enable room-temperature operation of the single-electron devices. A major achievement of this research has been the creation of a new single-electron device structure within the framework of current CMOS technology which has allowed for the fabrication of single-electron devices on a large scale and in parallel process. This was made possible by employing a vertical electrode configuration where the source and the drain electrodes were separated by a thin layer of dielectric medium (∼10 nm). Next, Coulomb islands were attached to the exposed sidewalls of the dielectric film using a combination of colloidal and surface chemistry. Individually addressable gate electrodes were then incorporated in devices, also in complete parallel processing. Subsequent I-V measurements of these devices have yielded Coulomb blockade, Coulomb staircase, and Coulomb oscillations at room temperature and at low temperature. A systematic study of the single-electron charging/tunneling was carried out utilizing different sizes of Coulomb islands. The dependence of the nature of the Coulomb blockade and Coulomb staircase on nanoparticle size, temperature, and location of the Coulomb island were also investigated. Simulations based on the orthodox theory are in excellent agreement with the experimental results. Another challenge toward the realization of nanoscale devices is to develop a technique which enables an accurate and reliable positioning of nanostructures onto the targeted locations. Combining wet chemistry and CMOS fabrication technology, a method was developed which enables precise positioning of nanoparticles in the gap between two electrodes. Such precise positioning of nanoparticles could be utilized to improve the yield of single-electron devices.

Metalens as one of the most popular applications of emmerging optical metasurfaces has raised widspread interest recently. With nano structures fully controlling phase, polarization and transmission, metalens has achieved comparable performance of commercial objective lenses. While recent studies seeking for the accomplishment of traditional focusing behaviors through metalens are successful, inthis work, we have discovered that instead of focusing light to a point, metasurface further enables shaping the focus into a flexibly designed pattern, with more promises and potentials. New mechanism and generalizations of conventional point-focused metalens guiding principles have been proposed with metalens concentrating light to artificial focus pattern. As proving examples, we have demonstrated the engineering of metalens with artificial focus pattern by creating line and ring-shaped focus as 'drawing tools'. The metalens with 'U' and 'M' shaped focus are characterized for the proof of concepts. These metalens are fabricated through a single layer of silicon-based material through CMOS compatible nano fabrication process. The mechanism to generate artificial focus pattern can be applied to a plethora of future on-chip optical devices with applications ranging from beam engineering to next generation nano lithography.

The serine protease granzyme B, which is secreted by cytotoxic cells, is one of the major effectors of apoptosis in susceptible targets. To examine the apoptotic mechanism of granzyme B, we have analyzed its effect on purified proteins that are thought to be components of death pathways inherent to cells. We demonstrate that granzyme B processes interleukin 1β -converting enzyme (ICE) and the ICE-related protease Yama (also known as CPP32 or apopain) by limited proteolysis. Processing of ICE does not lead to activation. However, processing by granzyme B leads directly to the activation of Yama, which is now able to bind inhibitors and cleave the substrate poly(ADP-ribose) polymerase whose proteolysis is a marker of apoptosis initiated by several other stimuli. Thus ICE-related proteases can be activated by serine proteases that possess the correct specificity. Activation of pro-Yama by granzyme B is within the physiologic range. Thus the cytotoxic effect of granzyme B can be explained by its activation of an endogenous protease component of a programmed cell death pathway.