Phenotypic heterogeneity is widely observed in cancer cell populations. Here, to probe this heterogeneity, we developed an image-guided genomics technique termed spatiotemporal genomic and cellular analysis (SaGA) that allows for precise selection and amplification of living and rare cells. SaGA was used on collectively invading 3D cancer cell packs to create purified leader and follower cell lines. The leader cell cultures are phenotypically stable and highly invasive in contrast to follower cultures, which show phenotypic plasticity over time and minimally invade in a sheet-like pattern. Genomic and molecular interrogation reveals an atypical VEGF-based vasculogenesis signalling that facilitates recruitment of follower cells but not for leader cell motility itself, which instead utilizes focal adhesion kinase-fibronectin signalling. While leader cells provide an escape mechanism for followers, follower cells in turn provide leaders with increased growth and survival. These data support a symbiotic model of collective invasion where phenotypically distinct cell types cooperate to promote their escape.

BaTiO3/polyvinylidene fluoride (BT/PVDF) is the extensive reported composite material for application in modern electric devices. However, there still exists some obstacles prohibiting the further improvement of dielectric performance, such as poor interfacial compatibility and low dielectric constant. Therefore, in depth study of the size dependent polarization and surface modification of BT particle is of technological importance in developing high performance BT/PVDF composites. Here, a facile molten-salt synthetic method has been applied to prepare different grain sized BT particles through tailoring the calcination temperature. The size dependent spontaneous polarizationof BT particle was thoroughly investigated by theoretical calculation based on powder X-ray diffraction Rietveld refinement data. The results revealed that 600 nm sized BT particles possess the strong polarization, ascribing to the ferroelectric size effect. Furthermore, the surface of optimal BT particles has been modified by water-soluble polyvinylprrolidone (PVP) agent, and the coated particles exhibited fine core-shell structure and homogeneous dispersion in the PVDF matrix. The dielectric constant of the resulted composites increased significantly, especially, the prepared composite with 40 vol % BT loading exhibited the largest dielectric constant (65, 25 °C, 1 kHz) compared with the literature values of BT/PVDF at the same concentration of filler. Moreover, the energy storage density of the composites with tailored structure was largely enhanced at the low electric field, showing promising application as dielectric material in energy storage device. Our work suggested that introduction of strong polarized ferroelectric particles with optimal size and construction of core-shell structured coated fillers by PVP in the PVDF matrix are efficacious in improving dielectric performance of composites. The demonstrated approach can also be applied to the design and preparation of other polymers-based nanocomposites filled with ferroelectric particles to achieve desirable dielectric properties.

The findings in this study could broaden the applications of KNN materials in a new field.

Tough and conductive hydrogels are the promising materials for various applications. However, fabrication of these hydrogels at room or low temperatures, without external stimuli, is a challenge. Herein, a novel dual self-catalytic system composed of a variety of metal ions and catechol-based molecules was developed to efficiently trigger the free-radical polymerization of tough, conductive, transparent, and self-healing hydrogels at low temperature without any external stimuli. Ferric ions (Fe3+) and dopamine (DA) were chosen as model compounds, which form stable redox pairs that act as a dual self-catalytic system to activate ammonium persulfate to generate free radicals. Consequently, the radicals could rapidly trigger the hydrogel self-gelation at low temperatures (6 °C) within 5 s. The dual self-catalytic system opens up a facile route to synthesize multifunctional hydrogels at mild conditions for a broad range of applications, especially in tissue engineering and wearable electronics.

Abstract:High piezoelectricity of (K,Na)NbO 3 (KNN) lead-free materials benefits from a polymorphic phase transition (PPT) around room temperature, but its temperature sensitivity has been a bottleneck impeding their applications. We find that good thermal stability can be achieved in CaZrO 3 -modified KNN lead-free piezoceramics, in which the normalized strain d 33 * almost keeps constant from room temperature up to 140 o C. In situ synchrotron X-ray diffraction experiments combined with permitivity measurements disclose the occurrence of a new phase transformation under an electrical field, which extends the transition range between tetragonal and orthorhombic phases. It is revealed that such an electrically-enhanced diffused 2 polymorphic phase transition (EED-PPT) contributed to the boosted thermal stability of KNN based lead-free piezoceramics with high piezoelectricity. The present approach based on phase engineering should also be effective in endowing other lead-free piezoelectrics with high piezoelectricity and good temperature stability. IntroductionPiezoelectricity, a phenomenon whereby materials become electrically polarized upon the application of stress or deform in response to electrical stimuli, has been an active research topic since its discovery in 1880 by Pierre and Jacques Curie, because of its scientific interests and abundant applications. For the last half-century, the lead-contained materials, e.g., Pb(Zr,Ti)O 3 (PZT) and Pb(Mg,Nb)O 3 -PbTiO 3 (PMN-PT), have been the icons of piezoelectrics, exhibiting a morphotropic phase boundary (MPB), where plural phases with negligible difference in free energy coexist and strongly enhanced functional properties arise.[1] However, a possible toxicity of lead in PZT and PMN-PT has been raising intense health and environmental concerns; thus, the last decade has witnessed the surging dedication to viable lead-free alternatives. [2][3][4][5] Resembling the principle characteristics of MPB, [4][5][6][7][8][9][10] polymorphic phase transition (PPT) boundary has also been extensively pursued. [2, 11,12] Unfortunately, contrary to the nearly vertical MPB in the well-known PZT and PMN-PT systems, [1] the PPT in lead-free piezoelectrics is always tilted, resulting in unavoidable thermally unstable electromechanical properties. [13][14][15] Weak thermal stability is unacceptable for many industrial applications, even though lead-free piezoelectrics have competitive performance at ambient conditions. To address the issue, two approaches have been adopted so far, i.e., fabricating textured samples, [2] or shifting the PPT temperature T O-T well below room temperature. [13] However, the former confronts the poor reproducibility due to an excessively complex synthesis procedure; while the latter would inevitably sacrifice a large 3 portion of piezoelectric activity. Consequently, a barrier still exists in developing reliable lead-free piezomaterials as alternatives to currently market-dominating lead-based materials.Inspired by the nature of MPB in PZT and PMN-PT...

Adhesive hydrogels have broad applications ranging from tissue engineering to bioelectronics; however, fabricating adhesive hydrogels with multiple functions remains a challenge. In this study, a mussel-inspired tannic acid chelated-Ag (TA-Ag) nanozyme with peroxidase (POD)-like activity was designed by the in situ reduction of ultrasmall Ag nanoparticles (NPs) with TA. The ultrasmall TA-Ag nanozyme exhibited high catalytic activity to induce hydrogel self-setting without external aid. The nanozyme retained abundant phenolic hydroxyl groups and maintained the dynamic redox balance of phenol-quinone, providing the hydrogels with long-term and repeatable adhesiveness, similar to the adhesion of mussels. The phenolic hydroxyl groups also afforded uniform distribution of the nanozyme in the hydrogel network, thereby improving its mechanical properties and conductivity. Furthermore, the nanozyme endowed the hydrogel with antibacterial activity through synergistic effects of the reactive oxygen species generated via POD-like catalytic reactions and the intrinsic bactericidal activity of Ag. Owing to these advantages, the ultrasmall TA-Ag nanozyme-catalyzed hydrogel could be effectively used as an adhesive, antibacterial, and implantable bioelectrode to detect bio-signals, and as a wound dressing to accelerate tissue regeneration while preventing infection. Therefore, this study provides a promising approach for the fabrication of adhesive hydrogel bioelectronics with multiple functions via mussel-inspired nanozyme catalysis.

No abstract

Stacked transition-metal dichalcogenides on hexagonal boron nitride (h-BN) are platforms for high-performance electronic devices. However, such vertical stacks are usually constructed by the layer-by-layer polymer-assisted transfer of mechanically exfoliated layers. This inevitably causes interfacial contamination and device performance degradation. Herein, we develop a two-step, low-pressure chemical vapor deposition synthetic strategy incorporating the direct growth of monolayer h-BN on Au foil with the subsequent growth of MoS. In such vertical stacks, the interactions between MoS and Au are diminished by the intervening h-BN layer, as evidenced by the appearance of photoluminescence in MoS. The weakened interfacial interactions facilitate the transfer of the MoS/h-BN stacks from Au to arbitrary substrates by an electrochemical bubbling method. Scanning tunneling microscope/spectroscopy characterization shows that the central h-BN layer partially blocks the metal-induced gap states in MoS/h-BN/Au foils. The work offers insight into the synthesis, transfer, and device performance optimization of such vertically stacked heterostructures.