Bottom Contact 100 nm Channel-Length α-In2 Se3 In-Plane Ferroelectric Memory.

Owing to the emerging trend of non-volatile memory and data-centric computing, the demand for more functional materials and efficient device architecture at the nanoscale is becoming stringent. To date, 2D ferroelectrics are cultivated as channel materials in field-effect transistors for their retentive and switchable dipoles and flexibility to be compacted into diverse structures and integration for intensive production. This study demonstrates the in-plane (IP) ferroelectric memory effect of a 100 nm channel-length 2D ferroelectric semiconductor α-In2 Se3 stamped onto nanogap electrodes on Si/SiO2 under a lateral electric field. As α-In2 Se3 forms the bottom contact of the nanogap electrodes, a large memory window of 13 V at drain voltage between ±6.5 V and the on/off ratio reaching 103 can be explained by controlled IP polarization. Furthermore, the memory effect is modulated by the bottom gate voltage of the Si substrate due to the intercorrelation between IP and out-of-plane (OOP) polarization. The non-volatile memory characteristics including stable retention lasting 17 h, and endurance over 1200 cycles suggest a wide range of memory applications utilizing the lateral bottom contact structure.

Heat flow through a liquid-vapor interface in a nano-channel: the effect of end-grafting polymers on a wall.

Heat transfer through a liquid-vapor interface is a complex phenomenon and crucially relevant in heat-removal and cryogenic applications. The physical coupling among confining walls, liquid and vapor phases is very important for controlling or improving cooling rates or condensation efficiency. Surface modification is a promising route, which has been explored to taylor the heat transfer through confined two-phase systems. We use coarse-grained molecular-dynamics simulations to study the heat transfer through a nano-confined liquid-vapor interface as a function of fluid filling. We set up a stationary heat flow through a liquid-vapor interface, stabilized with the liquid in contact with a colder wall and a vapor in contact with a hotter wall. For these physical conditions, we perform extensive simulations by progressively increasing the number of fluid particles, i.e. the channel filling, and measure the fluid distribution in the channel, density, pressure and temperature profiles We also compare the heat flux behavior between a bare-surfaces nano-channel and others where the hot surface was coated with end-grafted polymers, with different wetting affinities and bending properties. We take extreme cases of polymer properties to obtain a general picture of the polymer effect on the heat transfer, as compared with the bare surfaces. We find that walls covered by end-grafted solvophylic polymers change the heat flux by a factor of 6, as compared with bare walls, if the liquid phase is in contact with the polymers. Once the liquid wets the coated wall, the improve on heat flux is smaller and dominated by the grafting density. We also find that for a wall coated with stiff polymers, the jump in heat flux takes place at a significantly lower channel filling, when the polymers' free ends interact with the liquid surface. Interestingly, the morphology of the polymers induces a 'liquid bridge' between the liquid phase and the hot wall, through which heat is transported with high (liquid-like) thermal conductivity.

Ultra-Sensitive and Selective Electrochemical Bio-Fluid Biopsy for Oral Cancer Screening.

The early diagnosis of recurrence and metastasis is critically important for decreasing the morbidity and mortality associated with oral cancers. Although liquid biopsy methods hold great promise that provide a successive "time-slice" profile of primary and metastatic oral cancer, the development of non-invasive, rapid, simple, and cost-effective liquid biopsy techniques remains challenging. In this study, an ultrasensitive and selective electrochemical liquid biopsy is developed for oral cancer screening based on tracking trace amounts of cancer biomarker by functionalized asymmetric nano-channels. Detection via antigen-antibody reactions is assayed by evaluating changes in ionic current. Upon the recognition of cancer biomarker antigens in bio-fluids, the inner wall of nano-channel immobilized with the corresponding antibodies undergoes molecular conformation transformation and surface physicochemical changes, which significantly regulate the ion transport through the nano-channel and help achieve sensitivity with a detection limit of 10-12 g mL-1 . Furthermore, owing to the specificity of the monoclonal antibody for the antigen, the nano-channel exhibits high selectivity for the biomarker than for structurally similar biological molecules present in bio-fluids. The effectiveness of this technique is confirmed through the diagnosis of clinical cases of oral squamous cell carcinoma. This study presents a novel diagnostic tool for oral cancer detection in bio-fluids.

Nano-porous SAPO-34 enhanced thin-film nanocomposite polymeric membrane: Simultaneously high water permeation and complete removal of cationic/anionic dyes from water.

Thin-film nanocomposite (TFN) membranes were prepared by embedding nano-porous SAPO-34 nanoparticles in a polypyrrole thin-film layer polymerized on PES substrate. SEM, EDX, AFM, hydrophilicity, zeta potential and MWCO measurements were applied to verify characteristics of membranes. TFN membranes presented considerably higher pure water permeability (by more than 300%) due to high hydrophilicity and also nano-channels created in thin-film. Performance of TFN membranes were also evaluated by removal of different anionic and cationic dyes (methyl violet 6B, reactive blue 4 and acid blue 193) from water. TFN membranes effectively removed 100% of all dyes from feed aqueous solutions with a low concentration (50 mg/l). Moreover, TFN membrane prepared with the highest amount of nano-filler presented an elevated water flux in filtration of solutions containing each dyes (e.g. more than 500% for reactive blue 4), a reduced flux decline ratio (36%) and also a higher flux recovery ratio (85%) in comparison with the pristine thin-film membrane, consequently indicating high performance of TFN membranes and potential of recovery just after a simple water washing. TFN membranes also revealed an efficient performance in filtration of high concentrations of dye solutions as well as in treatment of a real wastewater produced by a weaving company.

Three-step channel conformational changes common to DNA packaging motors of bacterial viruses T3, T4, SPP1, and Phi29.

The DNA packaging motor of dsDNA bacterial viruses contains a head-tail connector with a channel for the genome to enter during assembly and to exit during host infection. The DNA packaging motor of bacterial virus phi29 was recently reported to use the "One-way revolving" mechanism for DNA packaging. This raises a question of how dsDNA is ejected during infection if the channel acts as a one-way inward valve. Here we report a three step conformational change of the portal channel that is common among DNA translocation motors of bacterial viruses T3, T4, SPP1, and phi29. The channels of these motors exercise three discrete steps of gating, as revealed by electrophysiological assays. The data suggest that the three step channel conformational changes occur during DNA entry process, resulting in a structural transition in preparation for DNA movement in the reverse direction during ejection.

Atomic resolution imaging of beryl: an investigation of the nano-channel occupation.

Beryl in different varieties (emerald, aquamarine, heliodor etc.) displays a wide range of colours that have fascinated humans throughout history. Beryl is a hexagonal cyclo-silicate (ring-silicate) with channels going through the crystal along the c-axis. The channels are about 0.5 nm in diameter and can be occupied by water and alkali ions. Pure beryl (Be3 Al2 Si6 O18 ) is colourless (variety goshenite). The characteristic colours are believed to be mainly generated through substitutions with metal atoms in the lattice. Which atoms that are substituted is still debated it has been proposed that metal ions may also be enclosed in the channels and that this can also contribute to the crystal colouring. So far spectroscopy studies have not been able to fully answer this. Here we present the first experiments using atomic resolution scanning transmission electron microscope imaging (STEM) to investigate the channel occupation in beryl. We present images of a natural beryl crystal (variety heliodor) from the Bin Thuan Province in Vietnam. The channel occupation can be visualized. Based on the image contrast in combination with ex situ element analysis we suggest that some or all of the atoms that are visible in the channels are Fe ions.