Seamless Junctions Research Articles

Lateral Heterostructure Formed by Highly Thermally Conductive Fluorinated Graphene for Efficient Device Thermal Management.

The continued miniaturization of chips demands highly thermally conductive materials and effective thermal management strategies. Particularly, the high-field transport of the devices built with 2D materials is limited by self-heating. Here a systematic control of heat flow in single-side fluorinated graphene (FG) with varying degrees of fluorination is reported, revealing a superior room-temperature thermal conductivity as high as 128W m-1 K-1. Monolayer graphene/FG lateral heterostructures with seamless junctions are approached for device fabrication. Efficient in-plane heat removal paths from graphene channel to side FG are created, contributing significant reduction of the channel peak temperature and improvement in the current-carrying capability and power density. Molecular dynamics simulations indicate that the interfacial thermal conductance of the heterostructure is facilitated by the high degree of overlap in the phonon vibrational spectra. The findings offer novel design insights for efficient heat dissipation in micro- and nanoelectronic devices.

Nanoscale doping of polymeric semiconductors with confined electrochemical ion implantation.

Nanoresolved doping of polymeric semiconductors can overcome scaling limitations to create highly integrated flexible electronics, but remains a fundamental challenge due to isotropic diffusion of the dopants. Here we report a general methodology for achieving nanoscale ion-implantation-like electrochemical doping of polymeric semiconductors. This approach involves confining counterion electromigration within a glassy electrolyte composed of room-temperature ionic liquids and high-glass-transition-temperature insulating polymers. By precisely adjusting the electrolyte glass transition temperature (Tg) and the operating temperature (T), we create a highly localized electric field distribution and achieve anisotropic ion migration that is nearly vertical to the nanotip electrodes. The confined doping produces an excellent resolution of 56 nm with a lateral-extended doping length down to as little as 9.3 nm. We reveal a universal exponential dependence of the doping resolution on the temperature difference (Tg - T) that can be used to depict the doping resolution for almost infinite polymeric semiconductors. Moreover, we demonstrate its implications in a range of polymer electronic devices, including a 200% performance-enhanced organic transistor and a lateral p-n diode with seamless junction widths of <100 nm. Combined with a further demonstration in the scalability of the nanoscale doping, this concept may open up new opportunities for polymer-based nanoelectronics.

Flexible thermocouple using a thermoelectric graphene fiber with a seamless junction

Temperature is an important physical variable that indicates the condition of the human body and artificial systems. Advanced wearable applications require the development of temperature sensors with different form factors. In this study, a fiber-shaped thermoelectric temperature sensor is fabricated using a continuous graphene fiber whose two halves possess different reduction states. A seamless junction is formed by partially reducing a wet-spun graphene oxide fiber with hydroiodic acid (HI) solutions of different concentrations. One-half of the fiber is mildly reduced with 0.97 wt% HI, while the other half is highly reduced with 30.6 wt% HI. The different reduction states of the graphene composite fiber result in different Seebeck coefficients, allowing for the fabrication of a fiber-shaped graphene thermocouple without any laborious assembly. The flexible graphene thermocouple exhibits high sensitivity with a thermopower of 12.5 μV K–1 in the temperature range of room temperature to ∼70 °C. Furthermore, it exhibits high linearity with a correlation coefficient exceeding 0.995 and fast response with a time constant of 0.24 s. Owing to its mechanical robustness and flexibility, the stand-alone graphene thermocouple can be knitted into a cotton fabric glove, which presents a fast response to environmental changes without any external power source. This work offers a unique fabrication method for producing a high-performance, flexible thermocouple that features a seamless and clear junction without the use of additional materials. This alternative method eliminates the complicated assembly processes typically required for conventional thermocouples.

Gelation of Uniform Interfacial Diffusant in Embedded 3D Printing.

While the human body has many different examples of perfusable structures with complex geometries, biofabrication methods to replicate this complexity are still lacking. Specifically, the fabrication of self-supporting, branched networks with multiple channel diameters is particularly challenging. Here, we present the Gelation of Uniform Interfacial Diffusant in Embedded 3D Printing (GUIDE-3DP) approach for constructing perfusable networks of interconnected channels with precise control over branching geometries and vessel sizes. To achieve user-specified channel dimensions, this technique leverages the predictable diffusion of crosslinking reaction-initiators released from sacrificial inks printed within a hydrogel precursor. We demonstrate the versatility of GUIDE-3DP to be adapted for use with diverse physicochemical crosslinking mechanisms by designing seven printable material systems. Importantly, GUIDE-3DP allows for the independent tunability of both the inner and outer diameters of the printed channels and the ability to fabricate seamless junctions at branch points. This 3D bioprinting platform is uniquely suited for fabricating lumenized structures with complex shapes characteristic of multiple hollow vessels throughout the body. As an exemplary application, we demonstrate the fabrication of vasculature-like networks lined with endothelial cells. GUIDE-3DP represents an important advance toward the fabrication of self-supporting, physiologically relevant networks with intricate and perfusable geometries.

Laser-Induced Phase Transition and Patterning of hBN-Encapsulated MoTe2.

Transition metal dichalcogenides exhibit phase transitions through atomic migration when triggered by various stimuli, such as strain, doping, and annealing. However, since atomically thin 2D materials are easily damaged and evaporated from these strategies, studies on the crystal structure and composition of transformed 2D phases are limited. Here, the phase and composition change behavior of laser-irradiated molybdenum ditelluride (MoTe2 ) in various stacked geometry are investigated, and the stable laser-induced phase patterning in hexagonal boron nitride (hBN)-encapsulated MoTe2 is demonstrated. When air-exposed or single-side passivated 2H-MoTe2 are irradiated by a laser, MoTe2 is transformed into Te or Mo3 Te4 due to the highly accumulated heat and atomic evaporation. Conversely, hBN-encapsulated 2H-MoTe2 transformed into a 1T' phase without evaporation or structural degradation, enabling stable phase transitions in desired regions. The laser-induced phase transition shows layer number dependence; thinner MoTe2 has a higher phase transition temperature. From the stable phase patterning method, the low contact resistivity of 1.13kΩµm in 2H-MoTe2 field-effect transistors with 1T' contacts from the seamless heterophase junction geometry is achieved. This study paves an effective way to fabricate monolithic 2D electronic devices with laterally stitched phases and provides insights into phase and compositional changes in 2D materials.

Selective Electron Beam Patterning of Oxygen-Doped WSe2 for Seamless Lateral Junction Transistors.

Surface charge transfer doping (SCTD) using oxygen plasma to form a p‐type dopant oxide layer on transition metal dichalcogenide (TMDs) is a promising doping technique for 2D TMDs field‐effect transistors (FETs). However, patternability of SCTD is a key challenge to effectively switch FETs. Herein, a simple method to selectively pattern degenerately p‐type (p+)‐doped WSe2 FETs via electron beam (e‐beam) irradiation is reported. The effect of the selective e‐beam irradiation is confirmed by the gate‐tunable optical responses of seamless lateral p+–p diodes. The OFF state of the devices by inducing trapped charges via selective e‐beam irradiation onto a desired channel area in p+‐doped WSe2, which is in sharp contrast to globally p+‐doped WSe2 FETs, is realized. Selective e‐beam irradiation of the PMMA‐passivated p+‐WSe2 enables accurate control of the threshold voltage (V th) of WSe2 devices by varying the pattern size and e‐beam dose, while preserving the low contact resistance. By utilizing hBN as the gate dielectric, high‐performance WSe2 p‐FETs with a saturation current of −280 µA µm−1 and on/off ratio of 109 are achieved. This study's technique demonstrates a facile approach to obtain high‐performance TMD p‐FETs by e‐beam irradiation, enabling efficient switching and patternability toward various junction devices.

A comparison of DNA repair pathways to achieve a site-specific gene modification of the Bruton's tyrosine kinase gene

Gene editing utilizing homology-directed repair has advanced significantly for many monogenic diseases of the hematopoietic system in recent years but has also been hindered by decreases between in vitro and in vivo gene integration rates. Homology-directed repair occurs primarily in the S/G2 phases of the cell cycle, whereas long-term engrafting hematopoietic stem cells are typically quiescent. Alternative methods for a targeted integration have been proposed including homology-independent targeted integration and precise integration into target chromosome, which utilize non-homologous end joining and microhomology-mediated end joining, respectively. Non-homologous end joining occurs throughout the cell cycle, while microhomology-mediated end joining occurs predominantly in the S phase. We compared these pathways for the integration of a corrective DNA cassette at the Bruton’s tyrosine kinase gene for the treatment of X-linked agammaglobulinemia. Homology-directed repair generated the most integration in K562 cells; however, synchronizing cells into G1 resulted in the highest integration rates with homology-independent targeted integration. Only homology-directed repair produced seamless junctions, making it optimal for targets where insertions and deletions are impermissible. Bulk CD34+ cells were best edited by homology-directed repair and precise integration into the target chromosome, while sorted hematopoietic stem cells contained similar integration rates using all corrective donors.

One-Pot Synthesis of One-Dimensional Multijunction Semiconductor Nanochains from Cu1.94S, CdS, and ZnS for Photocatalytic Hydrogen Generation.

Chains of alternating semiconductor nanocrystals are complex nanostructures that can offer control over photogenerated charge carriers dynamics and quantized electronic states. We develop a simple one-pot colloidal synthesis of complex Cu1.94S-CdS and Cu1.94S-ZnS nanochains exploiting an equilibrium driving ion exchange mechanism. The chain length of the heterostructures can be tuned using a concentration dependent cation exchange mechanism controlled by the precursor concentrations, which enables the synthesis of monodisperse and uniform Cu1.94S-CdS-Cu1.94S nanochains featuring three epitaxial junctions. These seamless junctions enable efficient separation of photogenerated charge carriers, which can be harvested for photocatalytic applications. We demonstrate the superior photocatalytic activity of these noble metal free materials through solar hydrogen generation at a hydrogen evolution rate of 22.01 mmol g-1 h-1, which is 1.5-fold that of Pt/CdS heterostructure photocatalyst particles.

Room‐Temperature Nonvolatile Molecular Memory Based on Partially Unzipped Nanotube

AbstractNonvolatile memories have attracted a lot of interest because they retain the data when the power is interrupted. Smaller size and improved performance of nonvolatile memories are pursued both for basic research and applications. In this work, a molecular wire made of seamless junctions between semiconducting single‐walled carbon nanotubes (SWNT) and partially unzipped segments of the SWNTs are reported. This novel nanostructure is demonstrated to be a nonvolatile memory, which works at room temperature under atmospheric conditions. The characteristics of the device are measured with a four‐terminal configuration and a non‐local voltage (Vnon‐local) is used as the storage signal. An electrical hysteresis of Vnon‐local is observed, wherein two states with different Vnon‐local can be switched by the application of an electric field through an insulating gate device structure, exhibiting nonvolatile characteristics. Vnon‐local can be modulated with external magnetic fields and the mechanism of the electrical hysteresis is attributed to the magnetic moments at the partially unzipped SWNT. The smaller size of SWNT and high working temperature may lead to the development of molecular nanomagnets as nonvolatile memory devices for practical applications.

New automatic method for generating atomistic models of multi-branched and arbitrary-shaped seamless junctions of carbon nanostructures

This work proposes an original method for generating atomistic models of multi-branched and arbitrary-shaped seamless junctions of different nanostructures. Atomic frameworks of new hybrid systems with a wide variety of topological forms based on 1D and 2D structures can be obtained using this method. The topological diversity of generated hybrid systems is provided by the some features of the developed method. This method combines a triangulated nanomesh framework generation with a molecular dynamics (MD) method that allows us to generate dozens of topological configurations of the contact region of different objects. Energetically favorable junctions of carbon nanostructures, including Y- and X-shaped junctions of carbon nanotubes, a fullerene-nanotube junction, and a fullerene-graphene hybrid system are created using the developed original method.

A carbon nanotube-graphene nanoribbon seamless junction transistor.

The nature and type of intramolecular junctions are very important for nanoelectronics. Here, a new way of fabricating seamless junctions between carbon nanotubes and graphene nanoribbons (GNRs) is demonstrated. Dielectrophoretically aligned multi-walled carbon nanotubes (CNTs) across metal electrodes are etched with an Ar ion beam at low pressure. We show that grounding of metal electrodes plays an important role in the etching of CNTs in contact with the metal electrodes. If electrodes are grounded, that portion of the CNT doesn't get etched due to the discharge of ions through the ground, and CNT to GNR conversion occurs in the gap region between the metal electrodes. Thus produced GNRs have a large aspect ratio of ∼90, and Raman spectroscopy analysis shows that the distance between the defects is ∼65 nm. The CNT–GNR–CNT seamless junctions are ohmic in nature and the transistor shows a current on/off ratio of 27 with a hole mobility of 350 cm2 V−1 s−1.

Algorithm for constructing full-atomic models of X- and T-shaped seamless junctions between single-walled carbon nanotubes

Algorithm for constructing full-atomic models of X- and T-shaped seamless junctions between single-walled carbon nanotubes

Thermal Transport Behavior of Carbon Nanotube–Graphene Junction under Deformation

We employ molecular dynamics simulations to explore the effect of tensile strain on the thermal conductivity of carbon nanotube (CNT)–graphene junction structures. Two types of CNT–graphene junctions are simulated; a seamless junction between CNT and graphene with pure [Formula: see text] covalent bonds, and a junction with mixed [Formula: see text] covalent bonds are studied. The most interesting observation is that the thermal conductivity of a CNT–graphene junction structure increases with an increase in mechanical strain. For the case of a (6,6) CNT–graphene junction structure with an inter-pillar distance (the length of graphene floor between two CNT–graphene junctions) of 15[Formula: see text]nm, the thermal conductivity is improved by 22.4% with 0.1 tensile strain. The thermal conductivity improvement by mechanical strain is enhanced when a larger graphene floor is placed between junctions since a larger graphene floor allows larger deformation (larger tensile strain) without breaking bonds in the junction structure. However, the thermal conductivity is found to more strongly depend on the C–C bond hybridization at the intramolecular junctions with pure [Formula: see text] hybridization showing a higher thermal conductivity when compared to mixed [Formula: see text] bonding regardless of the amount of tensile strain. The obtained results will contribute to the development of flexible electronics by providing a theoretical background on the thermal transport of three-dimensional carbon nanostructures under deformation.

Study of seamless Au mesh flexible transparent heaters: Influence of mesh coverage

Here, we report on the experimental and theoretical understanding of seamless junction Au mesh network flexible transparent heaters. Three Au mesh transparent conductors (TCs) are fabricated using the photolithography-etching process to compare the influence of metal surface coverage on their electrical and thermal performance. The fabricated mesh networks are quite transparent (T ~ 80%) in the 400–900 nm spectral region and exhibit small variation in sheet resistance (ΔRmax ~ 0.12, 0.05, and 0.22 Ω □−1) under different bending radii (minimum radii of ~7.5 mm). The Au mesh with large surface coverage (i.e. ~4.8%) exhibited the highest figure of merit (1035), and the Au mesh with small surface coverage (i.e. ~2.5%), which eventually tested as a heater, exhibited the highest thermal efficiency (i.e. 249 °C/(W/cm2)) and temperature of 150 °C at the lowest input power (0.5 W cm−2). A 1D analytical heat transfer model is developed for quick estimation of temperature of heater samples. The thermal simulation of heaters is carried out using an ANSYS tool. The experimental, simulation and 1D analytical results are compared and validated, revealing that the simulation results are more aligned with experimental results. The flexible TCs with short response time and high thermal resistance are very useful in various flexible heating applications.

Transparent, Flexible Silicon Nanostructured Wire Networks with Seamless Junctions for High-Performance Photodetector Applications.

Optically transparent photodetectors are crucial in next-generation optoelectronic applications including smart windows and transparent image sensors. Designing photodetectors with high transparency, photoresponsivity, and robust mechanical flexibility remains a significant challenge, as is managing the inevitable trade-off between high transparency and strong photoresponse. Here we report a scalable method to produce flexible crystalline Si nanostructured wire (NW) networks fabricated from silicon-on-insulator (SOI) with seamless junctions and highly responsive porous Si segments that combine to deliver exceptional performance. These networks show high transparency (∼92% at 550 nm), broadband photodetection (350 to 950 nm) with excellent responsivity (25 A/W), optical response time (0.58 ms), and mechanical flexibility (1000 cycles). Temperature-dependent photocurrent measurements indicate the presence of localized electronic states in the porous Si segments, which play a crucial role in light harvesting and photocarrier generation. The scalable low-cost approach based on SOI has the potential to deliver new classes of flexible optoelectronic devices, including next-generation photodetectors and solar cells.

The Fusion of Imidazolium‐Based Ionic Polymer and Carbon Nanotubes: One Type of New Heteroatom‐Doped Carbon Precursors for High‐Performance Lithium–Sulfur Batteries

AbstractRational design of sulfur host materials with high electrical conductivity and strong polysulfides (PS) confinement is indispensable for high‐performance lithium–sulfur (Li–S) batteries. This study presents one type of new polymer material based on main‐chain imidazolium‐based ionic polymer (ImIP) and carbon nanotubes (CNTs); the polymer composites can serve as a precursor of CNT/NPC‐300, in which close coverage and seamless junction of CNTs by N‐doped porous carbon (NPC) form a 3D conductive network. CNT/NPC‐300 inherits and strengthens the advantages of both high electrical conductivity from CNTs and strong PS entrapping ability from NPC. Benefiting from the improved attributes, the CNT/NPC‐300‐57S electrode shows much higher reversible capacity, rate capability, and cycling stability than NPC‐57S and CNTs‐56S. The initial discharge capacity of 1065 mA h g−1 is achieved at 0.5 C with the capacity retention of 817 mA h g−1 over 300 cycles. Importantly, when counter bromide anion in the composite of CNTs and ImIP is metathesized to bis(trifluoromethane sulfonimide), heteroatom sulfur is cooperatively incorporated into the carbon hosts, and the surface area is increased with the promotion of micropore formation, thus further improving electrochemical performance. This provides a new method for optimizing porous properties and dopant components of the cathode materials in Li–S batteries.

Evaluation of pEASY-Uni Seamless Cloning and Assembly Kit to clone multiple fragments of Elaeis guineensis DNA

Several seamless DNA assembly kits based on in vitro homologous recombination activity are commercially available in recent years for efficient and rapid construction of expression vectors, subsequent transformation and investigation of gene functionality. This study was performed to estimate the efficiency of uni seamless cloning system, through cloning of multiple DNA fragments derived from Elaeis guineensis stearoyl-ACP desaturase (SAD) and metallothionein-like protein genes (MET1 and MET2) into a plasmid cloning vector. PCR fragments were assembled based on homologous overlapping regions of 25–30bp into a pUC19 linearized vector. The successful cloning of the three DNA fragments was validated by blue white screening, colony cracking and colony PCR. The observed overall cloning efficiency for the three assembled DNA fragments of about 2.7kb in size was above 65%. This system produces seamless junctions, is directional and does not rely on restriction enzyme digestion and any specific site within the DNA fragments.

Graphene Carbon Nanotube Carpets Grown Using Binary Catalysts for High-Performance Lithium-Ion Capacitors.

Here we show that a versatile binary catalyst solution of Fe3O4/AlOx nanoparticles enables homogeneous growth of single to few-walled carbon nanotube (CNT) carpets from three-dimensional carbon-based substrates, moving past existing two-dimensional limited growth methods. The binary catalyst is composed of amorphous AlOx nanoclusters over Fe3O4 crystalline nanoparticles, facilitating the creation of seamless junctions between the CNTs and the underlying carbon platform. The resulting graphene-CNT (GCNT) structure is a high-density CNT carpet ohmically connected to the carbon substrate, an important feature for advanced carbon electronics. As a demonstration of the utility of this approach, we use GCNTs as anodes and cathodes in binder-free lithium-ion capacitors, producing stable devices with high-energy densities (∼120 Wh kg-1), high-power density capabilities (∼20,500 W kg-1 at 29 Wh kg-1), and a large operating voltage window (4.3 to 0.01 V).

Rationally designed graphene-nanotube 3D architectures with a seamless nodal junction for efficient energy conversion and storage.

One-dimensional (1D) carbon nanotubes (CNTs) and 2D single-atomic layer graphene have superior thermal, electrical, and mechanical properties. However, these nanomaterials exhibit poor out-of-plane properties due to the weak van der Waals interaction in the transverse direction between graphitic layers. Recent theoretical studies indicate that rationally designed 3D architectures could have desirable out-of-plane properties while maintaining in-plane properties by growing CNTs and graphene into 3D architectures with a seamless nodal junction. However, the experimental realization of seamlessly-bonded architectures remains a challenge. We developed a strategy of creating 3D graphene-CNT hollow fibers with radially aligned CNTs (RACNTs) seamlessly sheathed by a cylindrical graphene layer through a one-step chemical vapor deposition using an anodized aluminum wire template. By controlling the aluminum wire diameter and anodization time, the length of the RACNTs and diameter of the graphene hollow fiber can be tuned, enabling efficient energy conversion and storage. These fibers, with a controllable surface area, meso-/micropores, and superior electrical properties, are excellent electrode materials for all-solid-state wire-shaped supercapacitors with poly(vinyl alcohol)/H2SO4 as the electrolyte and binder, exhibiting a surface-specific capacitance of 89.4 mF/cm(2) and length-specific capacitance up to 23.9 mF/cm, - one to four times the corresponding record-high capacities reported for other fiber-like supercapacitors. Dye-sensitized solar cells, fabricated using the fiber as a counter electrode, showed a power conversion efficiency of 6.8% and outperformed their counterparts with an expensive Pt wire counter electrode by a factor of 2.5. These novel fiber-shaped graphene-RACNT energy conversion and storage devices are so flexible they can be woven into fabrics as power sources.

Hot Fusion: an efficient method to clone multiple DNA fragments as well as inverted repeats without ligase.

Molecular cloning is utilized in nearly every facet of biological and medical research. We have developed a method, termed Hot Fusion, to efficiently clone one or multiple DNA fragments into plasmid vectors without the use of ligase. The method is directional, produces seamless junctions and is not dependent on the availability of restriction sites for inserts. Fragments are assembled based on shared homology regions of 17–30 bp at the junctions, which greatly simplifies the construct design. Hot Fusion is carried out in a one-step, single tube reaction at 50°C for one hour followed by cooling to room temperature. In addition to its utility for multi-fragment assembly Hot Fusion provides a highly efficient method for cloning DNA fragments containing inverted repeats for applications such as RNAi. The overall cloning efficiency is in the order of 90–95%.