Soap Film Transfer Printing for Ultrathin Electronics.

Flexible and stretchable electronics have attractive applications inaccessible to conventional rigid electronics. However, the mainstream transfer printing techniques have challenges for electronic films in terms of thickness and size and limitations for target substrates in terms of curvature, depth, and interfacial adhesion. Here a facile, damage-free, and contamination-free soap film transfer printing technique is reported that enables the wrinkle-free transfer of ultrathin electronic films, precise alignment in a transparent manner, and conformal and adhesion-independent printing onto various substrates, including those too topographically and adhesively challenging by existing methods. In principle, not only the pattern, resolution, and thickness of transferred films, but also the curvature, depth, and adhesion of target substrates are unlimited, while the size of transferred films can be as high as meter-scale. To demonstrate the capabilities of soap film transfer printing, pre-fabricated ultrathin electronics with multiple patterns, single micron resolution, sub-micron thickness, and centimeter size are conformably integrated onto the ultrathin web, ultra-soft cotton, DVD-R disk with the minimum radius of curvature of 131 nm, interior cavity of Klein bottle and dandelion with ultralow adhesion. The printed ultrathin sensors show superior conformabilities and robust adhesion, leading to engineering opportunities including electrocardiogram (ECG) signal acquisition and temperature measurement in aqueous environments.

Defect-guided self-tearing in graphene.

The two-dimensional to three-dimensional configuration transition through self-tearing promises the engineering and promising applications of graphene. However, it is challenging to control the tearing path on demand through common thermal and interfacial treatments. In this manuscript, a defect-guided self-tearing technique is proposed to generate wider, longer, and even curved and serrated configurations, which is impossible for defect-free graphene. The underlying tearing mechanisms regarding the advancing displacement are disclosed through molecular dynamics simulations and theoretical model. This study provides a useful guidance to the implementation of complex and functional three-dimensional graphene structures.

Bioinspired Environment-Adaptable and Ultrasensitive Multifunctional Electronic Skin for Human Healthcare and Robotic Sensations.

Multifunctional electronic skins (e-skins) that can sense various stimuli have demonstrated increasing potential in many fields. However, most e-skins are human-oriented that cannot work in hash environments such as high temperature, underwater, and corrosive chemicals, impairing their applications, especially in human-machine interfaces, intelligent machines, robotics, and so on. Inspired by the crack-shaped sensory organs of spiders, an environmentally robust and ultrasensitive multifunctional e-skin is developed. By developing a polyimide-based metal crack-localization strategy, the device has excellent environment adaptability since polyimide has high thermal stability and chemical durability. The localized cracked part serves as an ultrasensitive strain sensing unit, while the non-cracked serpentine part is solely responsible for temperature. Since the two units are made of the same material and process, the signals are decoupled easily. The proposed device is the first multifunctional e-skin that can be used in harsh environments, therefore is of great potential for both human and robot-oriented applications.

Thymoquinone induces apoptosis in temozolomide-resistant glioblastoma cells via the p38 mitogen-activated protein kinase signaling pathway.

Temozolomide (TMZ) can cross the blood-brain barrier (BBB) and deliver methyl groups to the purine (guanine) bases of DNA, leading to mispairing during DNA replication and subsequent cell death. However, increased expression of the repair enzyme methyl guanine methyltransferase (MGMT), which removes methyl groups from purine bases, counteracts methylation by TMZ. We evaluated the anticancer potential of thymoquinone (TQ), a hydrophobic flavonoid that inhibits resistance and induces apoptosis in various cancer cells, both in vitro and in vivo. In vitro experiments showed that compared with the Hs683 and M059J cell lines, U251 cells were more sensitive to TMZ. Compared to U251 cells, U251R cells, a TMZ drug-resistant strain established in this study, are characterized by increased expression of phosphorylated extracellular signal-regulated kinase (p-ERK) and MGMT. TQ treatments induced apoptosis in all cell lines. The p38 mitogen-activated protein kinase signal pathway was mainly activated in U251 and U251R cells; however, p-ERK and MGMT upregulation could not suppress TQ effects. Furthermore, si-p38 pretreatment of U251R cells in TQ treatments inhibited cell apoptosis. We speculate that TQ contributed to the phosphorylation and activation of p38, but not of ERK-induced apoptosis (irrespective of TMZ resistance). In vivo, U251R-derived tumors subcutaneously inoculated in nude mice exhibited significant tumor volume reduction after TQ or TQ + TMZ cotreatments. High-performance liquid chromatography assay confirmed the presence of TQ in murine brain tissues. Our findings demonstrate that TQ can effectively cross the BBB and function alone or in combination with TMZ to treat glioblastoma.

Photothermal Nanoconfinement Reactor: Boosting Chemical Reactivity with Locally High Temperature in a Confined Space.

A photothermal nanoconfinement reactor (PNCR) system is proposed and demonstrated by using hollow carbon nanospheres (HCNs) to enhance the performance of the chemical reaction. Under light irradiation, the local temperature of the HCN inner void space was much higher than the bulk solution temperature because the confined space concentrates heat and inhibits heat loss. Using the temperature-sensitive model reaction, peroxydisulfate (PDS) activation to oxidize micropollutant, it is shown that the degradation rate of sulfamethoxazole in the PNCR system is 7.1 times of that without nanoconfinement. It is further discovered that the high-quality local heat inside the nanoconfined space shifted the model reaction from an otherwise non-radical pathway to a radical-based pathway. This work provides an interesting strategy to produce a locally high temperature, which has a wide range of applications to energy and environmental fields.

Erk phosphorylation reduces the thymoquinone toxicity in human hepatocarcinoma.

Although enormous achievements have been made in targeted molecular therapies against hepatocellular carcinoma (HCC), the treatments can only prolong the life of patients with extrahepatic metastases. We evaluated thymoquinone (TQ), a compound from Nigella sativa Linn., for its anti-cancer effect on SK-Hep1 cells and HCC-xenograft nude mice. TQ effectively triggered cell death    and activated p38 and extracellular signal-regulated kinases (Erk) pathways up to 24 h after treatment in cells. TQ-induced cell death was reversed by p38 inhibitor; however, it was enhanced by si-Erk. The caspase3 activation and TUNEL assay revealed a stronger toxic effect upon co-treatment with TQ and si-Erk. Our study suggested that phosphorylation of p38 in SK-Hep1 cells constituted the major factor leading to cell apoptosis, whereas phosphorylation of Erk led to drug resistance. Furthermore, TQ therapeutic effect was improved upon Erk inhibition in HCC-xenograft nude mice. TQ could present excellent anti-HCC potential under suitable p-Erk inhibiting conditions.

Compression-driven collapse of nanotubes.

Nanotubes are prone to collapsing under compression due to the competition between the bending stiffness of the walls and the van der Waals interactions. The different radial morphologies during collapse may affect the electrical properties of nanotube, which may find promising potential applications in strain engineering. In this paper, the finite-deformation model is introduced to determine the radial morphologies, energy barrier and radial deformability of a nanotube under compression, in which the adhesion interactions are analytically obtained. The analytical solutions of the radial morphologies during compression are consistent with the molecular dynamics simulations results, indicating the effectiveness of the finite-deformation model. The analytical results reveal that both the energy barrier and the radial deformability show a decreasing tendency with the increase of the nanotube diameter.

Mechanics of the scrolling and folding of graphene.

The competition between the out-of-plane rigidity and the van der Waals interaction leads to the scrolled and folded structural configurations of graphene. These configuration changes, as compared with the initially planar geometry, significantly affect the electronic, optical and mechanical properties of graphene, promising exciting applications in graphene-nanoelectronics. We propose a finite-deformation theoretical model, in which no presumed assumptions on the geometries of deformed configurations are required. Both the predicted deformed profiles and the critical conditions show great agreements with molecular dynamics simulations results when compared with existing studies with simple geometrical assumptions. Moreover, MD simulations are performed to explore the morphology transitions between different configurations. It is observed that the folded configuration is energetically favorable for a short graphene sheet, while a long graphene sheet tends to scroll. Of particular interest, we observe the morphology transition from a Fermat scroll to the Archimedean scroll for the bi-scrolled graphene. These findings are useful for understanding the stability of graphene and may provide guidance to the design of programmable graphene-nanoelectronics.

Mechanics of the folding of a nanotube.

Nanotubes fold due to the competition between their mechanical stability and van der Waals interactions. The caused dramatic morphology change promises exciting applications of nanotubes in responsive and reconfigurable nanodevices. To investigate the folding mechanism, a curvature-based finite-deformation theoretical model simultaneously considering both the folding of a nanotube and the possible collapsing of the cross-section is developed. The predicted critical condition and the profiles in both axial and transverse directions agree well with molecular dynamics (MD) solutions, demonstrating that the cross-sectional deformation should be taken into account when investigating the folding of a nanotube with a large diameter. Moreover, simple scaling laws of the critical conditions are proposed through a small-deformation theoretical model. With these scaling laws, one can easily and quickly determine both the collapsing state of the cross-section and the folding state of the nanotube with only geometrical parameters [Formula: see text] rather than the difficult-to-determine material properties [Formula: see text].

Novel Environmentally Friendly RNAi Biopesticides: Targeting V-ATPase in Holotrichia parallela Larvae Using Layered Double Hydroxide Nanocomplexes.

RNA interference (RNAi)-based biopesticides offer an attractive avenue for pest control. Previous studies revealed high RNAi sensitivity in Holotrichia parallela larvae, showcasing its potential for grub control. In this study, we aimed to develop an environmentally friendly RNAi method for H. parallela larvae. The double-stranded RNA (dsRNA) of the V-ATPase-a gene (HpVAA) was loaded onto layered double hydroxide (LDH). The dsRNA/LDH nanocomplex exhibited increased environmental stability, and we investigated the absorption rate and permeability of dsRNA-nanoparticle complexes and explored the RNAi controlling effect. Silencing the HpVAA gene was found to darken the epidermis of H. parallela larvae, with growth cessation or death or mortality, disrupting the epidermis and midgut structure. Quantitative reverse transcription-polymerase chain reaction and confocal microscopy confirmed the effective absorption of the dsRNA/LDH nanocomplex by peanut plants, with distribution in roots, stems, and leaves. Nanomaterial-mediated RNAi silenced the target genes, leading to the death of pests. Therefore, these findings indicate the successful application of the nanomaterial-mediated RNAi system for underground pests, thus establishing a theoretical foundation for developing a green, safe, and efficient pest control strategy.

[Cloning, eukaryotic expression and spatial expression patterns of porcine MNSFbeta].

MNSFbeta (Monoclonal nonspecific suppressor factor beta) is a natural immunosuppressive factor which has been reported to be involved in various biological processes, such as immune responses, cell division, stress response, cell apoptosis, and nuclear transport. However, study on porcine MNSFbeta has been rarely reported. In this study, the full-length sequence of porcine MNSFbeta (GenBank accession number: KF77642500) was predicted in silicon and its cDNA sequence was obtained through RT-PCR from porcine spleen. The nucleic acid and protein sequences were analyzed. Then, the gene was subcloned into pEGFP-C1 to construct a recombinant plasmid pEGFP-MNSFbeta which was transfected into swine umbilical vein endothelial cells (SUVECs) using Lipofectamine 2000. The expression of GFP was detected by fluorescence microscopy, Western blot, and laser confocal fluorescence microscopy. The spatial expression patterns of porcine MNSFbeta were detected by real-time qPCR. Results showed that the full length of porcine MNSFbeta was 402 bp encoding 133 amino acids with only one exon. Bioinformatics analysis showed that porcine MNSFbeta protein was a stable protein consisting of a ubiquitin-like domain fused to the ribosomal protein S30 with no signal peptide. The analyses of homology and phylogenetic tree of porcine MNSFbeta and its homologs in other 18 species showed that the identities of MNSFbeta protein sequence were higher than 91% among different species and the evolutionary distance was less than 0.05. It indicates that MNSFbeta is highly conserved in the process of evolution. Fluorescence signal showed that the fusion protein GFP-MNSFbeta was successfully expressed in SUVECs which was then confirmed by Western blot. Laser confocal fluorescence microscopy showed that MNSFbeta was expressed in both nucleus and cytoplasm. Analysis of spatial expression patterns showed that procine MNSFbeta was widely expressed in immune tissues, but not in lung, suggesting that MNSFbeta may play an important role in immune response.

Auxetic Kirigami Metamaterials upon Large Stretching.

Auxetic kirigami metamaterials (KMs) attain negative Poisson's ratios with periodic slender cuts on thin sheets. The existing thin auxetic KMs forfeit auxeticity under large tensions because their auxeticity mainly arises from in-plane deformation, but out-of-plane buckling could arise to cause large deviations, and thicker KMs would suffer from stress failure. This paper proposes a novel family of KMs that can realize and retain auxeticity for up to 0.50 applied strains by fully exploiting out-of-plane buckling in the design model. Numerical and experimental results show that the designed KMs possess unique properties that are not exhibited by existing KMs, including a wide range of negative Poisson's ratios with designable variation modes under different applied strains, sheet thickness-insensitive auxeticity, and excellent shape recoverability. A potential application is exemplified with a scenario that they are designed as a stretchable display without image distortions under large tensions. The proposed auxetic KMs open new opportunities for the design of specific functional devices in areas of compliant robotics, bio-medical devices, and flexible electronics.

A nanonewton-scale biomimetic mechanosensor.

Biomimetic mechanosensors have profound implications for various areas, including health care, prosthetics, human‒machine interfaces, and robotics. As one of the most important parameters, the sensitivity of mechanosensors is intrinsically determined by the detection resolution to mechanical force. In this manuscript, we expand the force detection resolution of current biomimetic mechanosensors from the micronewton to nanonewton scale. We develop a nanocrack-based electronic whisker-type mechanosensor that has a detection resolution of 72.2 nN. We achieve the perception of subtle mechanical stimuli, such as tiny objects and airflow, and the recognition of surface morphology down to a 30 nm height, which is the finest resolution ever reported in biomimetic mechanosensors. More importantly, we explore the use of this mechanosensor in wearable devices for sensing gravity field orientation with respect to the body, which has not been previously achieved by these types of sensors. We develop a wearable smart system for sensing the body's posture and movements, which can be used for remote monitoring of falls in elderly people. In summary, the proposed device offers great advantages for not only improving sensing ability but also expanding functions and thus can be used in many fields not currently served by mechanosensors.

Waterproof AlInGaP optoelectronics on stretchable substrates with applications in biomedicine and robotics.

Inorganic light-emitting diodes and photodetectors represent important, established technologies for solid-state lighting, digital imaging and many other applications. Eliminating mechanical and geometrical design constraints imposed by the supporting semiconductor wafers can enable alternative uses in areas such as biomedicine and robotics. Here we describe systems that consist of arrays of interconnected, ultrathin inorganic light-emitting diodes and photodetectors configured in mechanically optimized layouts on unusual substrates. Light-emitting sutures, implantable sheets and illuminated plasmonic crystals that are compatible with complete immersion in biofluids illustrate the suitability of these technologies for use in biomedicine. Waterproof optical-proximity-sensor tapes capable of conformal integration on curved surfaces of gloves and thin, refractive-index monitors wrapped on tubing for intravenous delivery systems demonstrate possibilities in robotics and clinical medicine. These and related systems may create important, unconventional opportunities for optoelectronic devices.

Achieving directional propagation of elastic waves via topology optimization.

This paper presents a study on topology optimization of novel material microstructural configurations to achieve directional elastic wave propagation through maximization of partial band gaps. A waveguide incorporating a periodic-microstructure material may exhibit different propagation properties for the plane elastic waves incident from different inlets. A topology optimization problem is formulated to enhance such a property with a gradient-based mathematical programming algorithm. For alleviating the issue of local optimum traps, the random morphology description functions (RMDFs) are introduced to generate random initial designs for the optimization process. The optimized designs finally converge to the orderly material distribution and numerical validation shows improved directional propagation property as expected. The utilization of linear two-dimension phononic crystal with efficient partial band gap is suitable for directional propagation with a broad frequency range.

Multifunctional epidermal electronics printed directly onto the skin.

Materials and designs are presented for electronics and sensors that can be conformally and robustly integrated onto the surface of the skin. A multifunctional device of this type can record various physiological signals relevant to health and wellness. This class of technology offers capabilities in biocompatible, non-invasive measurement that lie beyond those available with conventional, point-contact electrode interfaces to the skin.