The uniform growth of single-crystal graphene over wafer-scale areas remains a challenge in the commercial-level manufacturability of various electronic, photonic, mechanical, and other devices based ...on graphene. Here, we describe wafer-scale growth of wrinkle-free single-crystal monolayer graphene on silicon wafer using a hydrogen-terminated germanium buffer layer. The anisotropic twofold symmetry of the germanium (110) surface allowed unidirectional alignment of multiple seeds, which were merged to uniform single-crystal graphene with predefined orientation. Furthermore, the weak interaction between graphene and underlying hydrogen-terminated germanium surface enabled the facile etch-free dry transfer of graphene and the recycling of the germanium substrate for continual graphene growth.
An active matrix‐type stretchable display is realized by overlay‐aligned transfer of inorganic light‐emitting diode (LED) and single‐crystal Si thin film transistor (TFT) with roll processes. The ...roll‐based transfer enables integration of heterogeneous thin film devices on a rubber substrate while preserving excellent electrical and optical properties of these devices, comparable to their bulk properties. The electron mobility of the integrated Si‐TFT is over 700 cm2 V−1 s−1, and this is attributed to the good interface between the Si channel and the thermally grown SiO2 insulator. The light emission properties of the LED are of wafer quality. The resulting display stably operates under tensile strains up to 40%, over 200 cycles, demonstrating the potential of stretchable displays based on inorganic materials.
All‐inorganic‐based stretchable active matrix display is demonstrated by integration of inorganic light‐emitting diode and single‐crystal Si thin film transistor. Overlay‐aligned roll transfer technique provides good integration of two devices on rubber substrate with outstanding electrical and optical properties. Furthermore, a serpentine‐shaped interconnector allows the effective strain division for stable operation of display over 40% applied strain.
Overcoming resistance: Heat‐treated cancer cells possess a protective mechanism for resistance and survival. Resistance‐free apoptosis‐inducing magnetic nanoparticles (RAINs) successfully promote ...hyperthermic apoptosis, obstructing cell survival by triggering two functional units of heat generation and the release of geldanamycin (GM) for heat shock protein (Hsp) inhibition under an alternating magnetic field (AMF).
Mechanical metamaterials possess unusual mechanical properties that cannot be found in nature. Auxetic metamaterials have negative Poisson's ratios and tend to expand in a direction perpendicular to ...the axial extension direction. When the Poisson's ratio of a display circuit board is forced to be −1 by adopting an auxetic metamaterial, a display can be stretchable without image distortion, and this display is called a meta‐display in this study. The critical obstacles to implementing a stretchable display are large stretchability, high deformation uniformity, and low image distortion. The meta‐display overcomes these obstacles by incorporating micro‐LEDs and a kirigami‐based auxetic circuit board. An auxetic meta‐display with a stretchability of 24.5%, Poisson's ratio of −1, and no image distortion under uniaxial stretching is demonstrated. Finally, the roll transfer process enabled the scaling‐up of a 3‐inch meta‐display attachable to surfaces with non‐zero Gaussian curvatures. This conformity to the non‐zero Gaussian curvature helps realize biomedical applications such as wearable display, phototherapy, and skincare.
An auxetic meta‐display overcomes the obstacles of conventional stretchable displays by realizing large stretchability, high deformation uniformity, and low image distortion. It is fabricated by transferring micro‐LEDs on the circuit board based on auxetic metamaterials, and exhibits conformal wrapping on non‐Gaussian surfaces, enabling a skin‐attachable biomedical device.
Additional surgeries for implantable biomedical devices are inevitable to replace discharged batteries, but repeated surgeries can be a risk to patients, causing bleeding, inflammation, and ...infection. Therefore, developing self‐powered implantable devices is essential to reduce the patient's physical/psychological pain and financial burden. Although wireless communication plays a critical role in implantable biomedical devices that contain the function of data transmitting, it has never been integrated with in vivo piezoelectric self‐powered system due to its high‐level power consumption (microwatt‐scale). Here, wireless communication, which is essential for a ubiquitous healthcare system, is successfully driven with in vivo energy harvesting enabled by high‐performance single‐crystalline (1 − x)Pb(Mg1/3Nb2/3)O3−(x)Pb(Zr,Ti)O3 (PMN‐PZT). The PMN‐PZT energy harvester generates an open‐circuit voltage of 17.8 V and a short‐circuit current of 1.74 µA from porcine heartbeats, which are greater by a factor of 4.45 and 17.5 than those of previously reported in vivo piezoelectric energy harvesting. The energy harvester exhibits excellent biocompatibility, which implies the possibility for applying the device to biomedical applications.
In vivo self‐powered wireless transmission using a flexible single‐crystalline piezoelectric energy harvester is demonstrated. The high‐performance energy harvester generates an output voltage of 17.8 V and a current of 1.75 µA from the contraction and relaxation motion of porcine heart. The energy from in vivo physiological motion enables self‐powered wireless transmission, thus realizing practical application in the ubiquitous healthcare system.
It is challenging to develop alloying anodes with ultrafast charging and large energy storage using bulk anode materials because of the difficulty of carrier‐ion diffusion and fragmentation of the ...active electrode material. Herein, a rational strategy is reported to design bulk Bi anodes for Na‐ion batteries that feature ultrafast charging, long cyclability, and large energy storage without using expensive nanomaterials and surface modifications. It is found that bulk Bi particles gradually transform into a porous nanostructure during cycling in a glyme‐based electrolyte, whereas the resultant structure stores Na ions by forming phases with high Na diffusivity. These features allow the anodes to exhibit unprecedented electrochemical properties; the developed Na–Bi half‐cell delivers 379 mA h g−1 (97% of that measured at 1C) at 7.7 A g−1 (20C) during 3500 cycles. It also retained 94% and 93% of the capacity measured at 1C even at extremely fast‐charging rates of 80C and 100C, respectively. The structural origins of the measured properties are verified by experiments and first‐principles calculations. The findings of this study not only broaden understanding of the underlying mechanisms of fast‐charging anodes, but also provide basic guidelines for searching battery anodes that simultaneously exhibit high capacities, fast kinetics, and long cycling stabilities.
With the difficulty in simultaneously achieving a large capacity, ultrafast charging capability, and long cycling stability in a battery anode, a bulk Bi anode is presented for Na‐ion batteries that provides a simple yet practical route to address this issue without using expensive nanoscale materials and additional complex modifications.
Synthetic magnetic nanoparticles (MNPs) are emerging as versatile probes in biomedical applications, especially in the area of magnetic resonance imaging (MRI). Their size, which is comparable to ...biological functional units, and their unique magnetic properties allow their utilization as molecular imaging probes. Herein, we present an overview of recent breakthroughs in the development of new synthetic MNP probes with which the sensitive and target-specific observation of biological events at the molecular and cellular levels is possible.
Photolithography is the prevalent microfabrication technology. It needs to meet resolution and yield demands at a cost that makes it economically viable. However, conventional far-field ...photolithography has reached the diffraction limit, which imposes complex optics and short-wavelength beam source to achieve high resolution at the expense of cost efficiency. Here, we present a cost-effective near-field optical printing approach that uses metal patterns embedded in a flexible elastomer photomask with mechanical robustness. This technique generates sub-diffraction patterns that are smaller than 1/10
of the wavelength of the incoming light. It can be integrated into existing hardware and standard mercury lamp, and used for a variety of surfaces, such as curved, rough and defect surfaces. This method offers a higher resolution than common light-based printing systems, while enabling parallel-writing. We anticipate that it will be widely used in academic and industrial productions.
Current biomedical imaging techniques including magnetic resonance imaging (MRI), positron emission tomography (PET), and computed X-ray tomography (CT) are vital in the diagnosis of various ...diseases. Each imaging modality has its own merits and disadvantages, and a single technique does not possess all the required capabilities for comprehensive imaging. Therefore, multimodal imaging methods are quickly becoming important tools for state-of-the-art biomedical research and clinical diagnostics and therapeutics. In this Account, we will discuss synergistically integrated nanoparticle probes, which will be an essential tool in multimodal imaging technology. When inorganic nanoparticles are introduced into biological systems, their extremely small size and their exceptional physical and chemical properties make them useful probes for biological diagnostics. Nanoparticle probes can endow imaging techniques with enhanced signal sensitivity, better spatial resolution, and the ability to relay information about biological systems at the molecular and cellular levels. Simple magnetic nanoparticles function as MRI contrast enhancement probes. These magnetic nanoparticles can then serve as a core platform for the addition of other functional moieties including fluorescence tags, radionuclides, and other biomolecules for multimodal imaging, gene delivery, and cellular trafficking. For example, MRI−optical dual-modal probes composed of a fluorescent dye-doped silica (DySiO2) core surrounded by magnetic nanoparticles can macroscopically detect neuroblastoma cancer cells via MRI along with subcellular information via fluorescence imaging. Magnetic nanoparticles can also be coupled to radionuclides (124I) to construct MRI−PET dual-modal probes. Such probes can accurately detect lymph nodes (LNs), which are critical for assessing cancer metastasis. In vivo MRI/PET images can clearly identify small (∼3 mm) LNs along with precise anatomical information. Systems using multicomponent nanoparticles modified with biomolecules can also monitor gene expression and other markers in cell therapeutics studies. We have used hybrid stem cell−magnetic nanoparticle probes with MRI to monitor in vivo stem cell trafficking. MRI with hybrid probes of magnetic nanoparticles and adenovirus can detect target cells and can monitor gene delivery and the expression of green fluorescent proteins optically. Each component of such multimodal probes complements the other modalities, and their synergistic materials properties ultimately provide more accurate information in in vitro and in vivo biological systems.
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