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We characterize terahertz wireless channels for extracting data from nanoscale sensors deployed within human lungs. We discover that the inhalation and exhalation of oxygen and carbon dioxide causes periodic variation of the absorption coefficient of the terahertz channel. Channel absorption drops to its minimum near the end of inhalation, providing a window of opportunity to extract data with minimum transmission power. We propose an algorithm for nanosensors to estimate the periodic channel by observing signal-to-noise ratio of the beacons transmitted from the data sink. Using real respiration data from multiple subjects, we demonstrate that the proposed algorithm can estimate the minimum absorption interval of the periodic channel with 98.5% accuracy. Our analysis shows that by confining all data collections during the estimated low-absorption window of the periodic channel, nanosensors can reduce power consumption by six orders of magnitude. Finally, we demonstrate that for wireless communications within human lungs, 0.1–0.12 THz is the least absorbing spectrum within the terahertz band. [ABSTRACT FROM AUTHOR]

Abstract: Free-standing composite films based on graphene/polyaniline (PANI) nanostructure were synthesized for supercapacitor application. First, polyaniline nanospheres were prepared by microemulsion polymerization, followed by the incorporation of graphene oxide nanosheets by hierarchical organization. The cationic PANI nanospheres were attached to the anionic GO sheets by electrostatic interaction and hierarchical deposition of GO/PANI nanostructures on a membrane filter via targeted self-assembly. Subsequent in situ chemical reduction of GO using hydroiodic acid produced well-defined graphene/PANI nanostructures having interpenetrating network with 3D open structure. The in situ GO reduction enabled keeping the hierarchical organization intact. The flexible graphene/PANI film produced was tested as a supercapacitor electrode using voltammograms and Nyquist analysis. The electro-capacitance of the film (448F/g) was enhanced by 60% through the synergistic combination of graphene and PANI nanostructures. About 81% capacity retention was achieved for the composite compared to 38% for PANI alone after subjecting the samples to 5000 cyclic operations. [Copyright &y& Elsevier]

The inclusion of nanomaterials into biopolymeric matrices followed by three-dimensional printing is poised to open new horizons in tissue engineering by generating customized 3D structures with optimized properties and multifunctionality. In this review, we present an overview on nanostructured ceramic, metal, carbon and polymer materials integrated with hard and soft forms of biopolymers for manufacturing both acellular and cellular 3D tissue constructs using a range of 3D-printing and bioprinting techniques. Property enhancements and emergence of new functional characteristics of biopolymeric composites with the incorporation of nanomaterials, followed by 3D printing are of particular interest. Several methods, including fused deposition modelling, stereolithography, selective laser sintering and bioprinting using droplet, laser and extrusion assisted techniques are presented. Significant modifications via surface functionalization, biodegradation of scaffolds and the cytotoxicity of nanocomposites are discussed. The results derived from in vitro and in vivo analysis of stem cells and 3D printed scaffolds, their interactions and degradations are highlighted. Advances with multiple nanomaterials are also discussed with the advantages of harnessing the potential of 3D printing to produce unique multifunctional nanocomposites for tissue engineering. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editor discusses various reports within the issue on topics including wireless communication in terahertz (THz) band, nanonetworks, and effects of non-flat interface in human skin tissues.

Biocompatible and photostable fluorescent probes are crucial yet challenging to develop for visualising and tracking biological functions and interactions that occur in living organisms. We synthesised biocompatible CQDs with 15% QY and tested them for cellular and scaffold imaging at variable depths. The CQDs, synthesised from collagen under controlled and benign conditions in a hydrothermal reactor, were characterised for their key physicochemical properties. The fluorescence characteristics were determined using two-photon microscopy, and based on our results we propose a mechanism for CQD luminescence by combining the carbogenic core and edge-effect contributions to the PL behaviour. The bioimaging of cells embedded in a luminescent 3D printed scaffold showed that CQDs enable imaging at depths of about 1500 μm under biomimetic conditions. Real-time videography and imaging tests showed differential visualisation of individual cells and scaffold. The excellent photostability and non-photobleaching characteristics of CQDs make them suitable for long-term whole cell and tissue imaging via multi-photon microscopy. [ABSTRACT FROM AUTHOR]

Chiral metasurfaces exhibit extraordinary capabilities of steering polarization of electromagnetic waves; and hence offering enormous potential in development of ultrathin components for advanced photonic technologies such as quantum computing and communication, imaging, optical memories and logics. These structures are realized by periodically arranged subwavelength resolved artificial elements (metaelements). Metaelements are mainly metallic, dielectric or metal-dielectric based and their fabrication is a daunting task due to the associated complex fabrication methodologies involving serial, time-consuming processes and sophisticated instrumentation, hence limiting the growth, and application of these metasurfaces to its true potential. To mitigate these issues, we exploited the single-step fabrication capabilities of two-photon polymerization based lithography to generate a range of all-carbon-based dielectric chiral metasurfaces in a carbon-polymer nanocomposite resin. Additionally, theoretical responses of these structures are also calculated. These structures derive their responses from structural chirality. With the advantages of single-step fabrication of any arbitrary structure with sub-wavelength resolved features, along with the capability of rapid prototyping in the proposed material system; this work holds a great potential towards generation of all-carbon metamaterials and 3D metasurfaces for several advanced photonic and optical technologies. [Display omitted] • Two-photon active acrylate-carbon nanocomposites. • Additive manufacturing of chiral metasurfaces. • Optically active two- and three-dimensional micro/nanostructures. • Sub-wavelength resolved features via maskless, single step processing. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Intrinsic doping design to produce high intensity green emissive quantum dots. • Solvothermal synthesis in ethanol achieves excitation-independent two-photon fluorescence. • Sensing mechanism via Stern-Volmer formalism and fluorescence lifetime responses. • Platform for high sensitivity exogenous and endogenous ferric ion detection in live cells. Abstract Ferric ions play significant roles in human bodily functions, since both overload and deficiency can cause major physiological dysfunctions. Hence, engineering of sensitive, selective sensors to detect such ions merits attention. We found that certain CDs derived from a nitrogen-containing precursor (phthalocyanine) in suitable media could provide significant advantages. Excitation-independent carbon dots (CDs) were prepared through facile one-pot hydrothermal (W-CDs) and solvothermal (E-CDs) methods. Compared to W-CDs, ethanol-mediated E-CDs provide narrower particle size distribution, higher pyrrolic and pyridinic N-content, higher quantum yield ( Q Y E - C D s / Q Y W - C D s = 2.58), strong green luminescence, excellent biocompatibility and efficient two-photon absorption. The E-CDs enabled superior NIR excitable two-photon bioimaging of breast cancer cells at variable depths and fluorescence quenching (81% extinction) for 10–600 μM Fe3+ ions. The mechanism of sensing was elucidated based on the fluorescence lifetime and the Stern-Volmer formalism. Intracellular Fe3+ ion sensing was first confirmed with E-CDs for lysed MCF-7 cells and quenching was detected in direct proportion to Fe3+ concentration (0–80 μM test range) with an LOD of 10.8 nM. Next, MCF-7 cells supplemented with variable concentrations of Fe3+ were incubated with E-CDs for sensing intracellular Fe3+ in live cells. The E-CDs showed high sensitivity for sensing endogenous Fe3+ ions in a stress-induced cell-based model. [ABSTRACT FROM AUTHOR]