Moiré Pattern Controlled Phonon Polarizer Based on Twisted Graphene

Twisted van der Waals materials featuring Moiré patterns present new design possibilities and demonstrate unconventional behaviors in electrical, optical, spintronic, and superconducting properties. However, experimental exploration of thermal transport across Moiré patterns has not been as extensive, despite its critical role in nanoelectronics, thermal management, and energy technologies. Here, the first experimental study is conducted on thermal transport across twisted graphene, demonstrating a phonon polarizer concept from the rotational misalignment between stacked layers. The direct thermal and acoustic measurements, structural characterizations, and atomistic modeling, reveal a modulation up to 631% in thermal conductance with various Moiré angles, while maintaining a high acoustic transmission. By comparing experiments with density functional theory and molecular dynamics simulations, mode-dependent phonon transmissions are quantified based on the angle alignment of graphene band structures and attributed to the coupling among flexural phonon modes. The agreement confirms the dominant tuning mechanisms in adjusting phonon transmission from high-frequency thermal modes while having negligible effects on low-frequency acoustic modes near Brillouin zone center. This study offers crucial insights into the fundamental thermal transport in Moiré structures, opening avenues for the invention of quantum thermal devices and new design methodologies based on manipulations of vibrational band structures and phonon spectra.

Photosensitizer-singlet oxygen sensor conjugated silica nanoparticles for photodynamic therapy and bioimaging

Intracellular singlet oxygen (1O2) generation and detection help optimize the outcome of photodynamic therapy (PDT). Theranostics programmed for on-demand phototriggered 1O2 release and bioimaging have great potential to transform PDT. We demonstrate an ultrasensitive fluorescence turn-on sensor-sensitizer-RGD peptide-silica nanoarchitecture and its 1O2 generation-releasing-storing-sensing properties at the single-particle level or in living cells. The sensor and sensitizer in the nanoarchitecture are an aminomethyl anthracene (AMA)-coumarin dyad and a porphyrin or CdSe/ZnS quantum dots (QDs), respectively. The AMA in the dyad quantitatively quenches the fluorescence of coumarin by intramolecular electron transfer, the porphyrin or QD moiety generates 1O2, and the RGD peptide facilitates intracellular delivery. The small size, below 200 nm, as verified by scanning electron microscopy and differential light scattering measurements, of the architecture within the 1O2 diffusion length enables fast and efficient intracellular fluorescence switching by the tandem ultraviolet (UV)-visible or visible-near-infrared (NIR) photo-triggering. While the red emission and 1O2 generation by the porphyrin are continually turned on, the blue emission of coumarin is uncaged into 230-fold intensity enhancement by on-demand photo-triggering. The 1O2 production and release by the nanoarchitecture enable spectro-temporally controlled cell imaging and apoptotic cell death; the latter is verified from cytotoxic data under dark and phototriggering conditions. Furthermore, the bioimaging potential of the TCPP-based nanoarchitecture is examined in vivo in B6 mice.

Evolution of CRISPR-enabled biosensors for amplification-free nucleic acid detection

CRISPR biosensors enable rapid and accurate detection of nucleic acids without resorting to target amplification. Specifically, these systems facilitate the simultaneous detection of multiple nucleic acid targets with single-base specificity. This is an invaluable asset that can ultimately facilitate accurate diagnoses of biologically complex diseases.

Electrically gated molecular thermal switch

Controlling heat flow is a key challenge for applications ranging from thermal management in electronics to energy systems, industrial processing, and thermal therapy. However, progress has generally been limited by slow response times and low tunability in thermal conductance. In this work, we demonstrate an electronically gated solid-state thermal switch using self-assembled molecular junctions to achieve excellent performance at room temperature. In this three-terminal device, heat flow is continuously and reversibly modulated by an electric field through carefully controlled chemical bonding and charge distributions within the molecular interface. The devices have ultrahigh switching speeds above 1 megahertz, have on/off ratios in thermal conductance greater than 1300%, and can be switched more than 1 million times. We anticipate that these advances will generate opportunities in molecular engineering for thermal management systems and thermal circuit design.

Spin Polarization in Transport Studies of Chirality-Induced Spin Selectivity

Chirality-induced spin selectivity (CISS) is a recently discovered effect in which structural chirality can result in different conductivities for electrons with opposite spins. In the CISS community, the degree of spin polarization is commonly used to describe the efficiency of the spin filtering/polarizing process, as it represents the fraction of spins aligned along the chiral axis of chiral materials originating from non-spin-polarized currents. However, the methods of defining, calculating, and analyzing spin polarization have been inconsistent across various studies, hindering advances in this field. In this Perspective, we connect the relevant background and the definition of spin polarization, discuss its calculation in different contexts in the CISS, and propose a practical and meaningful figure of merit by quantitative analysis of magnetoresistance in CISS transport studies.

Fluorinated Silane-Modified Filtroporation Devices Enable Gene Knockout in Human Hematopoietic Stem and Progenitor Cells

Intracellular delivery technologies that are cost-effective, non-cytotoxic, efficient, and cargo-agnostic are needed to enable the manufacturing of cell-based therapies as well as gene manipulation for research applications. Current technologies capable of delivering large cargoes, such as plasmids and CRISPR-Cas9 ribonucleoproteins (RNPs), are plagued with high costs and/or cytotoxicity and often require substantial specialized equipment and reagents, which may not be available in resource-limited settings. Here, we report an intracellular delivery technology that can be assembled from materials available in most research laboratories, thus democratizing access to intracellular delivery for researchers and clinicians in low-resource areas of the world. These filtroporation devices permeabilize cells by pulling them through the pores of a cell culture insert by the application of vacuum available in biosafety cabinets. In a format that costs less than $10 in materials per experiment, we demonstrate the delivery of fluorescently labeled dextran, expression plasmids, and RNPs for gene knockout to Jurkat cells and human CD34+ hematopoietic stem and progenitor cell populations with delivery efficiencies of up to 40% for RNP knockout and viabilities of >80%. We show that functionalizing the surfaces of the filters with fluorinated silane moieties further enhances the delivery efficiency. These devices are capable of processing 500,000 to 4 million cells per experiment, and when combined with a 3D-printed vacuum application chamber, this throughput can be straightforwardly increased 6-12-fold in parallel experiments.

Poly-Catecholic Functionalization of Biomolecules for Rapid Gelation, Robust Injectable Bioadhesion, and Near-Infrared Responsiveness

Mussel-inspired catechol-functionalization of degradable natural biomaterials has garnered significant interest as an approach to achieve bioadhesion for sutureless wound closure. However, conjugation capacity in standard coupling reactions, such as carbodiimide chemistry, is limited by low yield and lack of abundant conjugation sites. Here, a simple oxidative polymerization step before conjugation of catechol-carrying molecules (i.e., 3,4-dihydroxy-l-phenylalanine, l-DOPA) as a potential approach to amplify catechol function in bioadhesion of natural gelatin biomaterials is proposed. Solutions of gelatin modified with poly(l-DOPA) moieties (GelDOPA) are characterized by faster physical gelation and increased viscosity, providing better wound control on double-curved tissue surfaces compared to those of l-DOPA-conjugated gelatin. Physical hydrogels treated topically with low concentrations of NaIO4 solutions are crosslinked on-demand via through-thickness diffusion. Poly(l-DOPA) conjugates enhance crosslinking density compared to l-DOPA conjugated gelatin, resulting in lower swelling and enhanced cohesion in physiological conditions. Together with cohesion, more robust bioadhesion at body temperature is achieved by poly(l-DOPA) conjugates, exceeding those of commercial sealants. Further, poly(l-DOPA) motifs introduced photothermal responsiveness via near-infrared (NIR) irradiation for controlled drug release and potential applications in photothermal therapy. The above functionalities, along with antibacterial activity, render the proposed approach an effective biomaterial design strategy for wound closure applications.

A push for mechanochemistry

Chemical reactions can be accelerated by directional local pressure applied to molecules.

Direct Bottom-Up In Situ Growth: A Paradigm Shift for Studies in Wet-Chemical Synthesis of Gold Nanoparticles

Plasmonic gold nanoparticles have been used increasingly in solid-state systems because of their applicability in fabricating novel sensors, heterogeneous catalysts, metamaterials, and thermoplasmonic substrates. While bottom-up colloidal syntheses take advantage of the chemical environment to control size, shape, composition, surface chemistry, and crystallography of the nanostructures precisely, it can be challenging to assemble nanoparticles rationally from suspension onto solid supports or within devices. In this Review, we discuss a powerful recent synthetic methodology, bottom-up in situ substrate growth, which circumvents time-consuming batch presynthesis, ligand exchange, and self-assembly steps by applying wet-chemical synthesis to form morphologically controlled nanostructures on supporting materials. First, we briefly introduce the properties of plasmonic nanostructures. Then we comprehensively summarize recent work that adds to the synthetic understanding of in situ geometrical and spatial control (patterning). Next, we briefly discuss applications of plasmonic hybrid materials prepared by in situ growth. Overall, despite the vast potential advantages of in situ growth, the mechanistic understanding of these methodologies remains far from established, providing opportunities and challenges for future research.

Exploring the Bottom-Up Growth of Anisotropic Gold Nanoparticles from Substrate-Bound Seeds in Microfluidic Reactors

We developed an unconventional seed-mediated in situ synthetic method, whereby gold nanostars are formed directly on the internal walls of microfluidic reactors. The dense plasmonic substrate coatings were grown in microfluidic channels with different geometries to elucidate the impacts of flow rate and profile on reagent consumption, product morphology, and density. Nanostar growth was found to occur in the flow-limited regime and our results highlight the possibility of creating shape gradients or incorporating multiple morphologies in the same microreactor, which is challenging to achieve with traditional self-assembly. The plasmonic-microfluidic platforms developed herein have implications for a broad range of applications, including cell culture/sorting, catalysis, sensing, and drug/gene delivery.

Technology Roadmap for Flexible Sensors

Humans rely increasingly on sensors to address grand challenges and to improve quality of life in the era of digitalization and big data. For ubiquitous sensing, flexible sensors are developed to overcome the limitations of conventional rigid counterparts. Despite rapid advancement in bench-side research over the last decade, the market adoption of flexible sensors remains limited. To ease and to expedite their deployment, here, we identify bottlenecks hindering the maturation of flexible sensors and propose promising solutions. We first analyze challenges in achieving satisfactory sensing performance for real-world applications and then summarize issues in compatible sensor-biology interfaces, followed by brief discussions on powering and connecting sensor networks. Issues en route to commercialization and for sustainable growth of the sector are also analyzed, highlighting environmental concerns and emphasizing nontechnical issues such as business, regulatory, and ethical considerations. Additionally, we look at future intelligent flexible sensors. In proposing a comprehensive roadmap, we hope to steer research efforts towards common goals and to guide coordinated development strategies from disparate communities. Through such collaborative efforts, scientific breakthroughs can be made sooner and capitalized for the betterment of humanity.

A Breathable, Passive-Cooling, Non-Inflammatory, and Biodegradable Aerogel Electronic Skin for Wearable Physical-Electrophysiological-Chemical Analysis

Real-time monitoring of human health can be significantly improved by designing novel electronic skin (E-skin) platforms that mimic the characteristics and sensitivity of human skin. A high-quality E-skin platform that can simultaneously monitor multiple physiological and metabolic biomarkers without introducing skin discomfort or irritation is an unmet medical need. Conventional E-skins are either monofunctional or made from elastomeric films that do not include key synergistic features of natural skin, such as multi-sensing, breathability, and thermal management capabilities in a single patch. Herein, a biocompatible and biodegradable E-skin patch based on flexible gelatin methacryloyl aerogel (FGA) for non-invasive and continuous monitoring of multiple biomarkers of interest is engineered and demonstrated. Taking advantage of cryogenic temperature treatment and slow polymerization, FGA is fabricated with a highly interconnected porous structure that displays good flexibility, passive-cooling capabilities, and ultra-lightweight properties that make it comfortable to wear for long periods of time. It also provides numerous permeable capillary channels for thermal-moisture transfer, ensuring its excellent breathability. Therefore, the engineered FGA-based E-skin can simultaneously monitor body temperature, hydration, and biopotentials via electrophysiological sensors and detect glucose, lactate, and alcohol levels via electrochemical sensors. This work offers a previously unexplored materials strategy for next-generation E-skin platforms with superior practicality.

Flexible and Implantable Polyimide Aptamer-Field-Effect Transistor Biosensors

Monitoring neurochemical signaling across time scales is critical to understanding how brains encode and store information. Flexible (vs stiff) devices have been shown to improve in vivo monitoring, particularly over longer times, by reducing tissue damage and immunological responses. Here, we report our initial steps toward developing flexible and implantable neuroprobes with aptamer-field-effect transistor (FET) biosensors for neurotransmitter monitoring. A high-throughput process was developed to fabricate thin, flexible polyimide probes using microelectromechanical-system (MEMS) technologies, where 150 flexible probes were fabricated on each 4 in. Si wafer. Probes were 150 μm wide and 7 μm thick with two FETs per tip. The bending stiffness was 1.2 × 10^-11 N·m². Semiconductor thin films (3 nm In₂O₃) were functionalized with DNA aptamers for target recognition, which produces aptamer conformational rearrangements detected via changes in FET conductance. Flexible aptamer-FET neuroprobes detected serotonin at femtomolar concentrations in high-ionic strength artificial cerebrospinal fluid. A straightforward implantation process was developed, where microfabricated Si carrier devices assisted with implantation such that flexible neuroprobes detected physiological relevant serotonin in a tissue-hydrogel brain mimic.

One-Step Bioprinting of Multi-Channel Hydrogel Filaments Using Chaotic Advection: Fabrication of Pre-Vascularized Muscle-Like Tissues

The biofabrication of living constructs containing hollow channels is critical for manufacturing thick tissues. However, current technologies are limited in their effectiveness in the fabrication of channels with diameters smaller than hundreds of micrometers. It is demonstrated that the co-extrusion of cell-laden hydrogels and sacrificial materials through printheads containing Kenics static mixing elements enables the continuous and one-step fabrication of thin hydrogel filaments (1 mm in diameter) containing dozens of hollow microchannels with widths as small as a single cell. Pre-vascularized skeletal muscle-like filaments are bioprinted by loading murine myoblasts (C2C12 cells) in gelatin methacryloyl - alginate hydrogels and using hydroxyethyl cellulose as a sacrificial material. Higher viability and metabolic activity are observed in filaments with hollow multi-channels than in solid constructs. The presence of hollow channels promotes the expression of Ki67 (a proliferation biomarker), mitigates the expression of hypoxia-inducible factor 1-alpha , and markedly enhances cell alignment (i.e., 82% of muscle myofibrils aligned (in ±10°) to the main direction of the microchannels after seven days of culture). The emergence of sarcomeric α-actin is verified through immunofluorescence and gene expression. Overall, this work presents an effective and practical tool for the fabrication of pre-vascularized engineered tissues.

Bio-macromolecular design roadmap towards tough bioadhesives

Emerging sutureless wound-closure techniques have led to paradigm shifts in wound management. State-of-the-art biomaterials offer biocompatible and biodegradable platforms enabling high cohesion (toughness) and adhesion for rapid bleeding control as well as robust attachment of implantable devices. Tough bioadhesion stems from the synergistic contributions of cohesive and adhesive interactions. This Review provides a biomacromolecular design roadmap for the development of tough adhesive surgical sealants. We discuss a library of materials and methods to introduce toughness and adhesion to biomaterials. Intrinsically tough and elastic polymers are leveraged primarily by introducing strong but dynamic inter- and intramolecular interactions either through polymer chain design or using crosslink regulating additives. In addition, many efforts have been made to promote underwater adhesion via covalent/noncovalent bonds, or through micro/macro-interlock mechanisms at the tissue interfaces. The materials settings and functional additives for this purpose and the related characterization methods are reviewed. Measurements and reporting needs for fair comparisons of different materials and their properties are discussed. Finally, future directions and further research opportunities for developing tough bioadhesive surgical sealants are highlighted.

Surface Lattice Plasmon Resonances by Direct In Situ Substrate Growth of Gold Nanoparticles in Ordered Arrays

Precise arrangements of plasmonic nanoparticles on substrates are important for designing optoelectronics, sensors and metamaterials with rational electronic, optical and magnetic properties. Bottom-up synthesis offers unmatched control over morphology and optical response of individual plasmonic building blocks. Usually, the incorporation of nanoparticles made by bottom-up wet chemistry starts from batch synthesis of colloids, which requires time-consuming and hard-to-scale steps like ligand exchange and self-assembly. Herein, an unconventional bottom-up wet-chemical synthetic approach for producing gold nanoparticle ordered arrays is developed. Water-processable hydroxypropyl cellulose stencils facilitate the patterning of a reductant chemical ink on which nanoparticle growth selectively occurs. Arrays exhibiting lattice plasmon resonances in the visible region and near infrared (quality factors of >20) are produced following a rapid synthetic step (<10 min), all without cleanroom fabrication, specialized equipment, or self-assembly, constituting a major step forward in establishing in situ growth approaches. Further, the technical capabilities of this method through modulation of the particle size, shape, and array spacings directly on the substrate are demonstrated. Ultimately, establishing a fundamental understanding of in situ growth has the potential to inform the fabrication of plasmonic materials; opening the door for in situ growth fabrication of waveguides, lasing platforms, and plasmonic sensors.

Engineered Hemostatic Biomaterials for Sealing Wounds

Hemostatic biomaterials show great promise in wound control for the treatment of uncontrolled bleeding associated with damaged tissues, traumatic wounds, and surgical incisions. A surge of interest has been directed at boosting hemostatic properties of bioactive materials via mechanisms triggering the coagulation cascade. A wide variety of biocompatible and biodegradable materials has been applied to the design of hemostatic platforms for rapid blood coagulation. Recent trends in the design of hemostatic agents emphasize chemical conjugation of charged moieties to biomacromolecules, physical incorporation of blood-coagulating agents in biomaterials systems, and superabsorbing materials in either dry (foams) or wet (hydrogel) states. In addition, tough bioadhesives are emerging for efficient and physical sealing of incisions. In this Review, we highlight the biomacromolecular design approaches adopted to develop hemostatic bioactive materials. We discuss the mechanistic pathways of hemostasis along with the current standard experimental procedures for characterization of the hemostasis efficacy. Finally, we discuss the potential for clinical translation of hemostatic technologies, future trends, and research opportunities for the development of next-generation surgical materials with hemostatic properties for wound management.

A Chirality-Based Quantum Leap

There is increasing interest in the study of chiral degrees of freedom occurring in matter and in electromagnetic fields. Opportunities in quantum sciences will likely exploit two main areas that are the focus of this Review: (1) recent observations of the chiral-induced spin selectivity (CISS) effect in chiral molecules and engineered nanomaterials and (2) rapidly evolving nanophotonic strategies designed to amplify chiral light-matter interactions. On the one hand, the CISS effect underpins the observation that charge transport through nanoscopic chiral structures favors a particular electronic spin orientation, resulting in large room-temperature spin polarizations. Observations of the CISS effect suggest opportunities for spin control and for the design and fabrication of room-temperature quantum devices from the bottom up, with atomic-scale precision and molecular modularity. On the other hand, chiral-optical effects that depend on both spin- and orbital-angular momentum of photons could offer key advantages in all-optical and quantum information technologies. In particular, amplification of these chiral light-matter interactions using rationally designed plasmonic and dielectric nanomaterials provide approaches to manipulate light intensity, polarization, and phase in confined nanoscale geometries. Any technology that relies on optimal charge transport, or optical control and readout, including quantum devices for logic, sensing, and storage, may benefit from chiral quantum properties. These properties can be theoretically and experimentally investigated from a quantum information perspective, which has not yet been fully developed. There are uncharted implications for the quantum sciences once chiral couplings can be engineered to control the storage, transduction, and manipulation of quantum information. This forward-looking Review provides a survey of the experimental and theoretical fundamentals of chiral-influenced quantum effects and presents a vision for their possible future roles in enabling room-temperature quantum technologies.

Template-Enabled Biofabrication of Thick 3D Tissues with Patterned Perfusable Macrochannels

Interconnected pathways in 3D bioartificial organs are essential to retaining cell activity in thick functional 3D tissues. 3D bioprinting methods have been widely explored in biofabrication of functionally patterned tissues; however, these methods are costly and confined to thin tissue layers due to poor control of low-viscosity bioinks. Here, cell-laden hydrogels that could be precisely patterned via water-soluble gelatin templates are constructed by economical extrusion 3D printed plastic templates. Tortuous co-continuous plastic networks, designed based on triply periodic minimal surfaces (TPMS), serve as a sacrificial pattern to shape the secondary sacrificial gelatin templates. These templates are eventually used to form cell-encapsulated gelatin methacryloyl (GelMA) hydrogel scaffolds patterned with the complex interconnected pathways. The proposed fabrication process is compatible with photo-crosslinkable hydrogels wherein prepolymer casting enables incorporation of high cell populations with high viability. The cell-laden hydrogel constructs are characterized by robust mechanical behavior. In vivo studies demonstrate a superior cell ingrowth into the highly permeable constructs compared to the bulk hydrogels. Perfusable complex interconnected networks within cell-encapsulated hydrogels may assist in engineering thick and functional tissue constructs through the permeable internal channels for efficient cellular activities in vivo.

Discovery and characterization of circulating tumor cell clusters in neuroendocrine tumor patients using nanosubstrate-embedded microchips

Circulating tumor cell (CTC) clusters are present in cancer patients with severe metastasis, resulting in poor clinical outcomes. However, CTC clusters have not been studied as extensively as single CTCs, and the clinical utility of CTC clusters remains largely unknown. In this study, we aim sought to explore the feasibility of NanoVelcro Chips to simultaneously detect both single CTCs and CTC clusters with negligible perturbation to their intrinsic properties in neuroendocrine tumors (NETs). We discovered frequent CTC clusters in patients with advanced NETs and examined their potential roles, together with single NET CTCs, as novel biomarkers of patient response following peptide receptor radionuclide therapy (PRRT). We observed dynamic changes in both total NET CTCs and NET CTC cluster counts in NET patients undergoing PRRT which correlated with clinical outcome. These preliminary findings suggest that CTC clusters, along with single CTCs, offer a potential non-invasive option to monitor the treatment response in NET patients undergoing PRRT.

Towards High-Performance Semitransparent Organic Photovoltaics: Dual-Functional p-Type Soft Interlayer

Semitransparent organic photovoltaics (OPVs) have drawn significant attention for their promising potential in the field of building integrated photovoltaics such as energy-generating greenhouses. However, the conflict between the need to attain satisfying average visible transmittances for greenhouse applications and the need to maintain high power conversion efficiencies is limiting the commercialization of semitransparent OPVs. A major manifestation of this issue is the undermining of charge carrier extraction efficiency when opaque, visible-light-absorbing electrodes are substituted with semitransparent ones. Here, we incorporated a dual-function p-type compatible interlayer to modify the interface of the hole-transporting layer and the ultrathin electrode of the semitransparent devices. We find that the p-type interlayer not only enhances the charge carrier extraction of the electrode but also increases the light transmittance in the wavelength range of 400-450 nm, which covers most of the photosynthetic absorption spectrum. The modified semitransparent devices reach a power conversion efficiency of 13.7% and an average visible transmittance of 22.2%.

Towards High-Performance Semitransparent Organic Photovoltaics: Dual-Functional p-Type Soft Interlayer

Semitransparent organic photovoltaics (OPVs) have drawn significant attention for their promising potential in the field of building integrated photovoltaics such as energy-generating greenhouses. However, the conflict between the need to attain satisfying average visible transmittances for greenhouse applications and the need to maintain high power conversion efficiencies is limiting the commercialization of semitransparent OPVs. A major manifestation of this issue is the undermining of charge carrier extraction efficiency when opaque, visible-light-absorbing electrodes are substituted with semitransparent ones. Here, we incorporated a dual-function p-type compatible interlayer to modify the interface of the hole-transporting layer and the ultrathin electrode of the semitransparent devices. We find that the p-type interlayer not only enhances the charge carrier extraction of the electrode but also increases the light transmittance in the wavelength range of 400-450 nm, which covers most of the photosynthetic absorption spectrum. The modified semitransparent devices reach a power conversion efficiency of 13.7% and an average visible transmittance of 22.2%.

Extraction of Hidden Science from Nanoscale Images

Scanning probe microscopies and spectroscopies enable investigation of surfaces and even buried interfaces down to the scale of chemical-bonding interactions, and this capability has been enhanced with the support of computational algorithms for data acquisition and image processing to explore physical, chemical, and biological phenomena. Here, we describe how scanning probe techniques have been enhanced by some of these recent algorithmic improvements. One improvement to the data acquisition algorithm is to advance beyond a simple rastering framework by using spirals at constant angular velocity then switching to constant linear velocity, which limits the piezo creep and hysteresis issues seen in traditional acquisition methods. One can also use image-processing techniques to model the distortions that appear from tip motion effects and to make corrections to these images. Another image-processing algorithm we discuss enables researchers to segment images by domains and subdomains, thereby highlighting reactive and interesting disordered sites at domain boundaries. Lastly, we discuss algorithms used to examine the dipole direction of individual molecules and surface domains, hydrogen bonding interactions, and molecular tilt. The computational algorithms used for scanning probe techniques are still improving rapidly and are incorporating machine learning at the next level of iteration. That said, the algorithms are not yet able to perform live adjustments during data recording that could enhance the microscopy and spectroscopic imaging methods significantly.

Wearable aptamer-field-effect transistor sensing system for noninvasive cortisol monitoring

Wearable technologies for personalized monitoring require sensors that track biomarkers often present at low levels. Cortisol—a key stress biomarker—is present in sweat at low nanomolar concentrations. Previous wearable sensing systems are limited to analytes in the micromolar-millimolar ranges. To overcome this and other limitations, we developed a flexible field-effect transistor (FET) biosensor array that exploits a previously unreported cortisol aptamer coupled to nanometer-thin-film In₂O₃ FETs. Cortisol levels were determined via molecular recognition by aptamers where binding was transduced to electrical signals on FETs. The physiological relevance of cortisol as a stress biomarker was demonstrated by tracking salivary cortisol levels in participants in a Trier Social Stress Test and establishing correlations between cortisol in diurnal saliva and sweat samples. These correlations motivated the development and on-body validation of an aptamer-FET array–based smartwatch equipped with a custom, multichannel, self-referencing, and autonomous source measurement unit enabling seamless, real-time cortisol sweat sensing.

Epidermis-Inspired Wearable Piezoresistive Pressure Sensors Using Reduced Graphene Oxide Self-Wrapped Copper Nanowire Networks

Wearable piezoresistive sensors are being developed as electronic skins (E-skin) for broad applications in human physiological monitoring and soft robotics. Tactile sensors with sufficient sensitivities, durability, and large dynamic ranges are required to replicate this critical component of the somatosensory system. Multiple micro/nanostructures, materials, and sensing modalities have been reported to address this need. However, a trade-off arises between device performance and device complexity. Inspired by the microstructure of the spinosum at the dermo epidermal junction in skin, a low-cost, scalable, and high-performance piezoresistive sensor is developed with high sensitivity (0.144 kPa^-1 ), extensive sensing range ( 0.1-15 kPa), fast response time (less than 150 ms), and excellent long-term stability (over 1000 cycles). Furthermore, the piezoresistive functionality of the device is realized via a flexible transparent electrode (FTE) using a highly stable reduced graphene oxide self-wrapped copper nanowire network. The developed nanowire-based spinosum microstructured FTEs are amenable to wearable electronics applications.

Nanotechnology for a Sustainable Future: Addressing Global Challenges with the International Network4Sustainable Nanotechnology

Nanotechnology has important roles to play in international efforts in sustainability. We discuss how current and future capabilities in nanotechnology align with and support the United Nations' Sustainable Development Goals. We argue that, as a field, we can accelerate the progress toward these goals both directly through technological solutions and through our special interdisciplinary skills in communication and tackling difficult challenges. We discuss the roles of targeting solutions, technology translation, the circular economy, and a number of examples from national efforts around the world in reaching these goals. We have formed a network of leading nanocenters to address these challenges globally and seek to recruit others to join us.

Optimizing cluster survey designs for estimating trachomatous inflammation-follicular within trachoma control programs

OBJECTIVES

The World Health Organization recommends mass drug administration (MDA) with azithromycin to eliminate trachoma as a public health problem. MDA decisions are based on prevalence estimates from two-stage cluster surveys. Work remains to mathematically evaluate current trachoma survey designs. We aimed to characterize the effects of the number of units sampled on the precision and cost of trachomatous inflammation-follicular (TF) estimates.

METHODS

We simulated a population of 30 districts to represent the breadth of possible TF distributions in Amhara, Ethiopia. Samples of varying numbers of clusters (14-34) and households (10-60) were selected. Sampling schemes were evaluated on precision, proportion of incorrect and low MDA decisions made, and estimated cost.

RESULTS

Number of clusters sampled had a greater impact on precision than number of households. The most efficient scheme depended on the underlying TF prevalence in a district. For lower prevalence areas (<10%) the most cost efficient (providing adequate precision while minimizing cost) design was 20 clusters of 20-30 households. For higher prevalence areas (>10%), the most efficient design was 15-20 clusters of 20-30 households.

CONCLUSIONS

For longer-running programs, using context-specific survey designs would allow for practical precision while reducing survey costs. Sampling 15 clusters of 20-30 households in suspected moderate to high prevalence districts and 20 clusters of 20-30 households in districts suspected to be near the 5% threshold appears to be a balanced approach.

Implantable aptamer-field-effect transistor neuroprobes for in vivo neurotransmitter monitoring

While tools for monitoring in vivo electrophysiology have been extensively developed, neurochemical recording technologies remain limited. Nevertheless, chemical communication via neurotransmitters plays central roles in brain information processing. We developed implantable aptamer–field-effect transistor (FET) neuroprobes for monitoring neurotransmitters. Neuroprobes were fabricated using high-throughput microelectromechanical system (MEMS) technologies, where 150 probes with shanks of either 150- or 50-μm widths and thicknesses were fabricated on 4-inch Si wafers. Nanoscale FETs with ultrathin (~3 to 4 nm) In₂O₃ semiconductor films were prepared using sol-gel processing. The In₂O₃ surfaces were coupled with synthetic oligonucleotide receptors (aptamers) to recognize and to detect the neurotransmitter serotonin. Aptamer-FET neuroprobes enabled femtomolar serotonin detection limits in brain tissue with minimal biofouling. Stimulated serotonin release was detected in vivo. This study opens opportunities for integrated neural activity recordings at high spatiotemporal resolution by combining these aptamer-FET sensors with other types of Si-based implantable probes to advance our understanding of brain function.

Silver nanoparticles boost charge-extraction efficiency in Shewanella microbial fuel cells

[Figure: see text].

Stretchable and Bioadhesive Gelatin Methacryloyl-Based Hydrogels Enabled by in Situ Dopamine Polymerization

Hydrogel patches with high toughness, stretchability, and adhesive properties are critical to healthcare applications including wound dressings and wearable devices. Gelatin methacryloyl (GelMA) provides a highly biocompatible and accessible hydrogel platform. However, low tissue adhesion and poor mechanical properties of cross-linked GelMA patches (i.e., brittleness and low stretchability) have been major obstacles to their application for sealing and repair of wounds. Here, we show that adding dopamine (DA) moieties in larger quantities than those of conjugated counterparts to the GelMA prepolymer solution followed by alkaline DA oxidation could result in robust mechanical and adhesive properties in GelMA-based hydrogels. In this way, cross-linked patches with ∼140% stretchability and ∼19 000 J/m³ toughness, which correspond to ∼5.7 and ∼3.3× improvement, respectively, compared to that of GelMA controls, were obtained. The DA oxidization in the prepolymer solution was found to play an important role in activating adhesive properties of cross-linked GelMA patches (∼4.0 and ∼6.9× increase in adhesion force under tensile and shear modes, respectively) due to the presence of reactive oxidized quinone species. We further conducted a parametric study on the factors such as UV light parameters, the photoinitiator type (i.e., lithium phenyl-2,4,6-trimethylbenzoylphosphinate, LAP, versus 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, Irgacure 2959), and alkaline DA oxidation to tune the cross-linking density and thereby hydrogel compliance for better adhesive properties. The superior adhesion performance of the resulting hydrogel along with in vitro cytocompatibility demonstrated its potential for use in skin-attachable substrates.

Fabrication of Multilayered Composite Nanofibers Using Continuous Chaotic Printing and Electrospinning: Chaotic Electrospinning

Multi-material and multilayered micro- and nanostructures are prominently featured in nature and engineering and are recognized by their remarkable properties. Unfortunately, the fabrication of micro- and nanostructured materials through conventional processes is challenging and costly. Herein, we introduce a high-throughput, continuous, and versatile strategy for the fabrication of polymer fibers with complex multilayered nanostructures. Chaotic electrospinning (ChE) is based on the coupling of continuous chaotic printing (CCP) and electrospinning, which produces fibers with an internal multi-material microstructure. When a CCP printhead is used as an electrospinning nozzle, the diameter of the fibers is further scaled down by 3 orders of magnitude while preserving their internal structure. ChE enables the use of various polymer inks for the creation of nanofibers with a customizable number of internal nanolayers. Our results showcase the versatility and tunability of ChE to fabricate multilayered structures at the nanoscale at high throughput. We apply ChE to the synthesis of unique carbon textile electrodes composed of nanofibers with striations carved into their surface at regular intervals. These striated carbon electrodes with high surface areas exhibit 3- to 4-fold increases in specific capacitance compared to regular carbon nanofibers; ChE holds great promise for the cost-effective fabrication of electrodes for supercapacitors and other applications.

Whitlockite-Enabled Hydrogel for Craniofacial Bone Regeneration

Growth-factor-free bone regeneration remains a challenge in craniofacial engineering. Here, we engineered an osteogenic niche composed of a commercially modified alginate hydrogel and whitlockite microparticles (WHMPs), which impart tunable physicochemical properties that can direct osteogenesis of human gingival mesenchymal stem cells (GMSCs). Our in vitro studies demonstrate that WHMPs induce osteogenesis of GMSCs more effectively than previously demonstrated hydroxyapatite microparticles (HApMPs). Alginate-WHMP hydrogels showed higher elasticity without any adverse effects on the viability of the encapsulated GMSCs. Moreover, the alginate-WHMP hydrogels upregulate the mitogen-activated protein kinase (MAPK) pathway, which in turn orchestrates several osteogenic markers, such as RUNX2 and OCN, in the encapsulated GMSCs. Concurrent coculture studies with human osteoclasts demonstrate that GMSCs encapsulated in alginate-WHMP hydrogels downregulate osteoclastic activity, potentially due to release of Mg2+ ions from the WHMPs along with secretion of osteoprotegerin from the GMSCs. In vivo studies demonstrated that the GMSCs encapsulated in our osteogenic niche were able to promote bone repair in calvarial defects in murine models. Altogether, our results confirmed the development of a promising treatment modality for craniofacial bone regeneration based on an injectable growth-factor-free hydrogel delivery system.

Entrepreneurial Talent Building for 21st Century Agricultural Innovation

Agricultural innovation is a key component of the global economy and enhances food security, health, and nutrition. Current innovation efforts focus mainly on supporting the transition to sustainable food systems, which is expected to harness technological advances across a range of fields. In this Nano Focus, we discuss how such efforts would benefit from not only supporting farmer participation in deciding transition pathways but also in fostering the interdisciplinary training and development of entrepreneurial-minded farmers, whom we term "AgTech Pioneers", to participate in cross-sector agricultural innovation ecosystems as cocreators and informed users of developing and future technologies. Toward this goal, we discuss possible strategies based on talent development, cross-disciplinary educational and training programs, and innovation clusters to build an AgTech Pioneer ecosystem, which can help to reinvigorate interest in farming careers and to identify and address challenges and opportunities in agriculture by accelerating and applying advances in nanoscience, nanotechnology, and related fields.

Single-Step Dual-Layer Photolithography for Tunable and Scalable Nanopatterning

Conventional photolithography, due to its scalability, robustness, and straightforward processes, has been widely applied to micro- and nanostructure manufacturing in electronics, optics, and biology. However, optical diffraction limits the ultimate resolution of conventional photolithography, which hinders its potential in nanoscale patterning for broader applications. Here, we introduce a derivative of conventional photolithography for nanoscale patterning called dual-layer photolithography (DLPL), which is based on the controlled exposure and development of overlapping positive and negative photoresists. In a typical experiment, substrates are sequentially coated by two layers of photoresists (both positive and negative). Then, we purposefully control the exposure time to generate slightly larger features in the positive photoresist than those in the negative photoresist. After development, their overlapping areas become the final features, which outline the original features. We demonstrate line widths down to 300 nm here, which can be readily improved with more precise control. By adjusting the lithography parameters and material deposition, the feature sizes, shapes (e.g., rings, numbers, letters), line widths (300-900 nm), and materials (e.g., SiO₂, Cr, and Ag) of these features can be independently controlled. Combined with anisotropic etching, more complex three-dimensional nanostructures can be fabricated as well, as we demonstrate here with Si. We further fabricate photodetectors as an example application to show that these nanostructures fabricated by DLPL can be used to promote light-trapping MAPbI₃ perovskite films to achieve good photoelectric properties. This strategy is not limited to ultraviolet photolithography and may also be incorporated into other energetic beam-based lithographic approaches, including deep and extreme ultraviolet photolithographies and electron beam lithography, to enhance their resolution.

Supramolecular Nanosubstrate-Mediated Delivery for CRISPR/Cas9 Gene Disruption and Deletion

The clustered regularly interspaced short palindromic repeats (CRISPR)-associated protein 9 (CRISPR/Cas9) is an efficient and precise gene-editing technology that offers a versatile solution for establishing treatments directed at genetic diseases. Currently, CRISPR/Cas9 delivery into cells relies primarily on viral vectors, which suffer from limitations in packaging capacity and safety concerns. These issues with a nonviral delivery strategy are addressed, where Cas9•sgRNA ribonucleoprotein (RNP) complexes can be encapsulated into supramolecular nanoparticles (SMNP) to form RNP⊂SMNPs, which can then be delivered into targeted cells via supramolecular nanosubstrate-mediated delivery. Utilizing the U87 glioblastoma cell line as a model system, a variety of parameters for cellular-uptake of the RNP-laden nanoparticles are examined. Dose- and time-dependent CRISPR/Cas9-mediated gene disruption is further examined in a green fluorescent protein (GFP)-expressing U87 cell line (GFP-U87). The utility of an optimized SMNP formulation in co-delivering Cas9 protein and two sgRNAs that target deletion of exons 45-55 (708 kb) of the dystrophin gene is demonstrated. Mutations in this region lead to Duchenne muscular dystrophy, a severe genetic muscle wasting disease. Efficient delivery of these gene deletion cargoes is observed in a human cardiomyocyte cell line (AC16), induced pluripotent stem cells, and mesenchymal stem cells.

Additively Manufactured Gradient Porous Ti-6Al-4V Hip Replacement Implants Embedded with Cell-Laden Gelatin Methacryloyl Hydrogels

Laser additive manufacturing has led to a paradigm shift in the design of next-generation customized porous implants aiming to integrate better with the surrounding bone. However, conflicting design criteria have limited the development of fully functional porous implants; increasing porosity improves body fluid/cell-laden prepolymer permeability at the expense of compromising mechanical stability. Here, functionally gradient porosity implants and scaffolds designed based on interconnected triply periodic minimal surfaces (TPMS) are demonstrated. High local porosity is defined at the implant/tissue interface aiming to improve the biological response. Gradually decreasing porosity from the surface to the center of the porous constructs provides mechanical strength in selective laser melted Ti-6Al-4V implants. The effect of unit cell size is studied to discover the printability limit where the specific surface area is maximized. Furthermore, mechanical studies on the unit cell topology effects suggest that the bending-dominated architectures can provide significantly enhanced strength and deformability, compared to stretching-dominated architectures. A finite element (FE) model developed also showed great predictability (within ∼13%) of the mechanical responses of implants to physical activities. Finally, in vitro biocompatibility studies were conducted for two-dimensional (2D) and three-dimensional (3D) cases. The results of the 2D in conjunction with surface roughness show favored physical cell attachment on the implant surface. Also, the results of the 3D biocompatibility study for the scaffolds incorporated with a cell-laden gelatin methacryloyl (GelMA) hydrogel show excellent viability. The design procedure proposed here provides new insights into the development of porous hip implants with simultaneous high mechanical and biological responses.

X-ray-Based Techniques to Study the Nano-Bio Interface

X-ray-based analytics are routinely applied in many fields, including physics, chemistry, materials science, and engineering. The full potential of such techniques in the life sciences and medicine, however, has not yet been fully exploited. We highlight current and upcoming advances in this direction. We describe different X-ray-based methodologies (including those performed at synchrotron light sources and X-ray free-electron lasers) and their potentials for application to investigate the nano-bio interface. The discussion is predominantly guided by asking how such methods could better help to understand and to improve nanoparticle-based drug delivery, though the concepts also apply to nano-bio interactions in general. We discuss current limitations and how they might be overcome, particularly for future use in vivo.

Large-Scale Soft-Lithographic Patterning of Plasmonic Nanoparticles

Micro- and nanoscale patterned monolayers of plasmonic nanoparticles were fabricated by combining concepts from colloidal chemistry, self-assembly, and subtractive soft lithography. Leveraging chemical interactions between the capping ligands of pre-synthesized gold colloids and a polydimethylsiloxane stamp, we demonstrated patterning gold nanoparticles over centimeter-scale areas with a variety of micro- and nanoscale geometries, including islands, lines, and chiral structures (e.g., square spirals). By successfully achieving nanoscale manipulation over a wide range of substrates and patterns, we establish a powerful and straightforward strategy, nanoparticle chemical lift-off lithography (NP-CLL), for the economical and scalable fabrication of functional plasmonic materials with colloidal nanoparticles as building blocks, offering a transformative solution for designing next-generation plasmonic technologies.

Seeded-Growth Experiment Demonstrating Size- and Shape-Dependence on Gold Nanoparticle-Light Interactions

Gold nanoparticles are exciting materials in nanotechnology and nanoscience research and are being applied across a wide range of fields including imaging, chemical sensing, energy storage, and cancer therapies. In this experiment, students will synthesize two sizes of gold nanospheres (~20 nm and ~100 nm) and will create gold nanostars utilizing a seed-mediated growth synthetic approach. Students will compare how each sample interacts differently with light (absorption and scattering) based on the nanoparticles' size and shape. This experiment is ideal for high-school and early undergraduate students since all reagents are non-toxic, affordable, and no special characterization equipment is required.

Narrower Nanoribbon Biosensors Fabricated by Chemical Lift-off Lithography Show Higher Sensitivity

Wafer-scale nanoribbon field-effect transistor (FET) biosensors fabricated by straightforward top-down processes are demonstrated as sensing platforms with high sensitivity to a broad range of biological targets. Nanoribbons with 350 nm widths (700 nm pitch) were patterned by chemical lift-off lithography using high-throughput, low-cost commercial digital versatile disks (DVDs) as masters. Lift-off lithography was also used to pattern ribbons with 2 μm or 20 μm widths (4 or 40 μm pitches, respectively) using masters fabricated by photolithography. For all widths, highly aligned, quasi-one-dimensional (1D) ribbon arrays were produced over centimeter length scales by sputtering to deposit 20 nm thin-film In₂O₃ as the semiconductor. Compared to 20 μm wide microribbons, FET sensors with 350 nm wide nanoribbons showed higher sensitivity to pH over a broad range (pH 5 to 10). Nanoribbon FETs functionalized with a serotonin-specific aptamer demonstrated larger responses to equimolar serotonin in high ionic strength buffer than those of microribbon FETs. Field-effect transistors with 350 nm wide nanoribbons functionalized with single-stranded DNA showed greater sensitivity to detecting complementary DNA hybridization vs 20 μm microribbon FETs. In all, we illustrate facile fabrication and use of large-area, uniform In₂O₃ nanoribbon FETs for ion, small-molecule, and oligonucleotide detection where higher surface-to-volume ratios translate to better detection sensitivities.