Precisely Patterned Channels in a Vertical Organic Electrochemical Transistor with a Diazirine Photo-Crosslinker

Organic electrochemical transistors (OECTs) rely on both efficient ionic doping/de-doping process and carrier transport in the mixed ionic-electronic channel under the modulation of gate bias. Moreover, channels that hold photopatterning capability are highly desired to minimize parasitic capacitance and simplify the fabrication process/cost. However, yielding photo-patternable channels with both precise/robust patterning capability and controllable ionic-electronic coupling is still challenging. Herein, double-end trifluoromethyl diazirines (DtFDA) with different chain lengths are introduced in the OECT channel to act as both photo-crosslinker and medium to regulate ionic-electronic transport. Specifically, high-resolution patterns with a minimum line width/gap of 2 μm are realized in p(g2T-T) or Homo-gDPP based channels by introducing DtFDA. Maximum transconductances of 68.6 mS and 81.6 mS, current on/off ratio of 106 and 107 (under a drain voltage of only ±0.1 V), are achieved in p- and n-type vertical OECTs (vOECTs), respectively, along with current densities exceeding 1 kA cm-2 and good cycling stability of more than 100,000 cycles (2000 seconds). This work provides a new and facile strategy for the fabrication of vOECT channels with high resolution and high performance via the introduction of a simple and efficient crosslinker.

Two orthogonal differentiation gradients locally coordinate fruit morphogenesis

Morphogenesis requires the coordination of cellular behaviors along developmental axes. In plants, gradients of growth and differentiation are typically established along a single longitudinal primordium axis to control global organ shape. Yet, it remains unclear how these gradients are locally adjusted to regulate the formation of complex organs that consist of diverse tissue types. Here we combine quantitative live imaging at cellular resolution with genetics, and chemical treatments to understand the formation of Arabidopsis thaliana female reproductive organ (gynoecium). We show that, contrary to other aerial organs, gynoecium shape is determined by two orthogonal, time-shifted differentiation gradients. An early mediolateral gradient controls valve morphogenesis while a late, longitudinal gradient regulates style differentiation. Local, tissue-dependent action of these gradients serves to fine-tune the common developmental program governing organ morphogenesis to ensure the specialized function of the gynoecium.

Laboratory Course Using Zebrafish to Uncover Changing Roles of Wnt Signaling in Early Vertebrate Development

Coordinated signaling pathway activity directs early patterning to set up the vertebrate body plan. Perturbations in the timing or location of signal molecule expression impacts embryo morphology and organ formation. In this study, we present a laboratory course to use zebrafish for studying the role of Wnt signaling in specifying the early embryonic axes. Students are exposed to basic techniques in molecular and developmental biology, including embryo manipulation, fluorescence microscopy, image processing, and data analysis. Furthermore, this course incorporates student-designed experiments to stimulate independent inquiry and improve scientific learning, providing an experience resembling graduate-level laboratory research. Students appreciated following vertebrate development in real-time, and principles of embryogenesis were reinforced by observing the morphological changes that arise due to signaling alterations. Scientific and research skills were enhanced through practice in experimental design, interpretation, and presentation.

Microsphere-Enabled Micropillar Array for Whispering Gallery Mode Virus Detection

Rapid detection of pathogens and analytes at the point of care offers an opportunity for prompt patient management and public health control. This paper reports an open microfluidic platform coupled with active whispering gallery mode (WGM) microsphere resonators for the rapid detection of influenza viruses. The WGM microsphere resonators, precoated with influenza A polyclonal antibodies, are mechanically trapped in the open micropillar array, where the evaporation-driven flow continuously transports a small volume (∼μL) of sample to the resonators without auxiliaries. Selective chemical modification of the pillar array changes surface wettability and flow pattern, which enhances the detection sensitivity of the WGM resonator-based virus sensor. The optofluidic sensing platform is able to specifically detect influenza A viruses within 15 min using a few microliters of sample and displays a linear response to different virus concentrations.

Nondestructive Direct Optical Patterning of Perovskite Nanocrystals with Carbene-Based Ligand Cross-Linkers

Microscale patterning of colloidal perovskite nanocrystals (NCs) is essential for their integration in advanced device platforms, such as high-definition displays. However, perovskite NCs usually show degraded optical and/or electrical properties after patterning with existing approaches, posing a critical challenge for their optoelectronic applications. Here we achieve nondestructive, direct optical patterning of perovskite NCs with rationally designed carbene-based cross-linkers and demonstrate their applications in high-performance light-emitting diodes. We reveal that both the photochemical properties and the electronic structures of cross-linkers need to be carefully tailored to the material properties of perovskite NCs. This method produces high-resolution (∼4000 ppi) NC patterns with preserved photoluminescent quantum efficiencies and charge transport properties. Prototype light-emitting diodes with patterned/cross-linked NC layers show a maximum luminance of over 60000 cd m-2 and a peak external quantum efficiency of 16%, among the highest for patterned perovskite electroluminescent devices. Such a material-adapted patterning method enabled by designs from a photochemistry perspective could foster the applications of perovskite NCs in system-level electronic and optoelectronic devices.

Room-Temperature Liquid Metals for Flexible Electronic Devices

Room-temperature gallium-based liquid metals (RT-GaLMs) have garnered significant interest recently owing to their extraordinary combination of fluidity, conductivity, stretchability, self-healing performance, and biocompatibility. They are ideal materials for the manufacture of flexible electronics. By changing the composition and oxidation of RT-GaLMs, physicochemical characteristics of the liquid metal can be adjusted, especially the regulation of rheological, wetting, and adhesion properties. This review highlights the advancements in the liquid metals used in flexible electronics. Meanwhile related characteristics of RT-GaLMs and underlying principles governing their processing and applications for flexible electronics are elucidated. Finally, the diverse applications of RT-GaLMs in self-healing circuits, flexible sensors, energy harvesting devices, and epidermal electronics, are explored. Additionally, the challenges hindering the progress of RT-GaLMs are discussed, while proposing future research directions and potential applications in this emerging field. By presenting a concise and critical analysis, this paper contributes to the advancement of RT-GaLMs as an advanced material applicable for the new generation of flexible electronics.

Deformation-Induced Photoprogrammable Pattern of Polyurethane Elastomers Based on Poisson Effect

Elastomers with high aspect ratio surface patterns are a promising class of materials for designing soft machines in the future. Here, a facile method for fabricating surface patterns on polyurethane elastomer by subtly utilizing the Poisson effect and gradient photocrosslinking is demonstrated. By applying uniaxial tensile strains, the aspect ratio of the surface patterns can be optionally manipulated. At prestretched state, the pattern on the polyurethane elastomer can be readily constructed through compressive stress, resulting from the gradient photocrosslinking via selective photodimerization of an anthracene-functionalized polyurethane elastomer (referred to as ANPU). The macromolecular aggregation structures during stretching deformation significantly contribute to the fabrication of high aspect ratio surface patterns. The insightful finite element analysis well demonstrates that the magnitude and distribution of internal stress in the ANPU elastomer can be regulated by selectively gradient crosslinking, leading to polymer chains migrate from the exposed region to the unexposed region, thereby generating a diverse array of surface patterns. Additionally, the periodic surface patterns exhibit tunable structural color according to the different stretching states and are fully reversible over multiple cycles, opening up avenues for diverse applications such as smart displays, stretchable strain sensors, and anticounterfeiting devices.

Injection Molding of Liquid Metal by Harnessing Nonstick Molds

The fluid nature of liquid metals combined with their ability to form a solid native oxide skin enables them to be patterned in ways that would be challenging for solid metals. The present work shows a unique way of patterning liquid metals by injecting liquid metals into a mold. The mold contains a nonstick coating that enables the removal of the mold, thereby leaving just the liquid metal on the target substrate. This approach offers the simplicity and structural control of molding but without having the mold become part of the device. Thus, the metal can be encapsulated with very soft polymers that collapse if used as microchannels. The same mold can be used multiple times for high-volume patterning of liquid metal. The injection molding method is rapid and reliably produces structures with complex geometries on both flat and curved surfaces. We demonstrate the method by fabricating an elastomeric Joule heater and an electroadhesive soft gripper to show the potential of the method for soft and stretchable devices.

Selected Area Manipulation of MoS2 via Focused Electron Beam-Induced Etching for Nanoscale Device Editing

We demonstrate direct-write patterning of single and multilayer MoS2 via a focused electron beam-induced etching (FEBIE) process mediated with the XeF2 precursor. MoS2 etching is performed at various currents, areal doses, on different substrates, and characterized using scanning electron and atomic force microscopies as well as Raman and photoluminescence spectroscopies. Scanning transmission electron microscopy reveals a sub-40 nm etching resolution and the progression of point defects and lateral etching of the consequent unsaturated bonds. The results confirm that the electron beam-induced etching process is minimally invasive to the underlying material in comparison to ion beam techniques, which damage the subsurface material. Single-layer MoS2 field-effect transistors are fabricated, and device characteristics are compared for channels that are edited via the selected area etching process. The source-drain current at constant gate and source-drain voltage scale linearly with the edited channel width. Moreover, the mobility of the narrowest channel width decreases, suggesting that backscattered and secondary electrons collaterally affect the periphery of the removed area. Focused electron beam doses on single-layer transistors below the etching threshold were also explored as a means to modify/thin the channel layer. The FEBIE exposures showed demonstrative effects via the transistor transfer characteristics, photoluminescence spectroscopy, and Raman spectroscopy. While strategies to minimize backscattered and secondary electron interactions outside of the scanned regions require further investigation, here, we show that FEBIE is a viable approach for selective nanoscale editing of MoS2 devices.

Developmental patterning function of GNOM ARF-GEF mediated from the cell periphery

The GNOM (GN) Guanine nucleotide Exchange Factor for ARF small GTPases (ARF-GEF) is among the best studied trafficking regulators in plants, playing crucial and unique developmental roles in patterning and polarity. The current models place GN at the Golgi apparatus (GA), where it mediates secretion/recycling, and at the plasma membrane (PM) presumably contributing to clathrin-mediated endocytosis (CME). The mechanistic basis of the developmental function of GN, distinct from the other ARF-GEFs including its closest homologue GNOM-LIKE1 (GNL1), remains elusive. Insights from this study largely extend the current notions of GN function. We show that GN, but not GNL1, localizes to the cell periphery at long-lived structures distinct from clathrin-coated pits, while CME and secretion proceed normally in gn knockouts. The functional GN mutant variant GNfewerroots, absent from the GA, suggests that the cell periphery is the major site of GN action responsible for its developmental function. Following inhibition by Brefeldin A, GN, but not GNL1, relocates to the PM likely on exocytic vesicles, suggesting selective molecular associations en route to the cell periphery. A study of GN-GNL1 chimeric ARF-GEFs indicates that all GN domains contribute to the specific GN function in a partially redundant manner. Together, this study offers significant steps toward the elucidation of the mechanism underlying unique cellular and development functions of GNOM.

Multi-Interfacial Confined Assembly of Colloidal Quantum Dots Quasisuperlattice Microcavities for High-Resolution Full-Color Microlaser Arrays

Colloidal quantum dots (CQDs) are considered a promising material for the next generation of integrated display devices due to their designable optical bandgap and low energy consumption. Owing to their dispersibility in solvents, CQD micro/nanostructures are generally fabricated by solution-processing methods. However, the random mass transfer in liquid restricts the programmable construction in macroscopy and ordered assembly in microscopy for the integration of CQD optical structures. Herein, a multi-interfacial confined assembly strategy is developed to fabricate CQDs programmable microstructure arrays with a quasisuperlattice configuration through controlling the dynamics of three-phase contact lines (TPCLs). The motion of TPCLs dominates the division of liquid film for precise positioning of CQD microstructures, while pinned TPCLs control the solvent evaporation and concentration gradient to directionally drive the mass transfer and packing of CQDs. Owing to their long-range order and adjustable structural dimensions, CQD microring arrays function as high-quality-factor (high-Q) lasing resonant cavities with low thresholds and tunable lasing emission modes. Through the further surface treatment and liquid dynamics control, the on-chip integration of red (R), green (G), and blue (B) multicomponent CQD microlaser arrays are demonstrated. The technique establishes a new route to fabricate large-area, ultrahigh-definition, and full-color CQD laser displays.

Controllable Multimodal Actuation in Fully Printed Ultrathin Micro-Patterned Electrochemical Actuators

Submillimeter or micrometer scale electrically controlled soft actuators have immense potential in microrobotics, haptics, and biomedical applications. However, the fabrication of miniaturized and micropatterned open-air soft actuators has remained challenging. In this study, we demonstrate the microfabrication of trilayer electrochemical actuators (ECAs) through aerosol jet printing (AJP), a rapid prototyping method with a 10 μm lateral resolution. We make fully printed 1000 × 5000 × 12 μm3 ultrathin ECAs, each of which comprises a Nafion electrolyte layer sandwiched between two poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) electrode layers. The ECAs actuate due to the electric-field-driven migration of hydrated protons. Due to the thinness that gives rise to a low proton transport length and a low flexural rigidity, the printed ECAs can operate under low voltages (∼0.5 V) and have a relatively fast response (∼seconds). We print all the components of an actuator that consists of two individually controlled submillimeter segments and demonstrate its multimodal actuation. The convenience, versatility, rapidity, and low cost of our microfabrication strategy promise future developments in integrating arrays of intricately patterned individually controlled soft microactuators on compact stretchable electronic circuits.

Petal abscission is promoted by jasmonic acid-induced autophagy at Arabidopsis petal bases

In angiosperms, the transition from floral-organ maintenance to abscission determines reproductive success and seed dispersion. For petal abscission, cell-fate decisions specifically at the petal-cell base are more important than organ-level senescence or cell death in petals. However, how this transition is regulated remains unclear. Here, we identify a jasmonic acid (JA)-regulated chromatin-state switch at the base of Arabidopsis petals that directs local cell-fate determination via autophagy. During petal maintenance, co-repressors of JA signaling accumulate at the base of petals to block MYC activity, leading to lower levels of ROS. JA acts as an airborne signaling molecule transmitted from stamens to petals, accumulating primarily in petal bases to trigger chromatin remodeling. This allows MYC transcription factors to promote chromatin accessibility for downstream targets, including NAC DOMAIN-CONTAINING PROTEIN102 (ANAC102). ANAC102 accumulates specifically at the petal base prior to abscission and triggers ROS accumulation and cell death via AUTOPHAGY-RELATED GENEs induction. Developmentally induced autophagy at the petal base causes maturation, vacuolar delivery, and breakdown of autophagosomes for terminal cell differentiation. Dynamic changes in vesicles and cytoplasmic components in the vacuole occur in many plants, suggesting JA-NAC-mediated local cell-fate determination by autophagy may be conserved in angiosperms.

Insights into the mechanisms of neuron generation and specification in the zebrafish ventral spinal cord

The vertebrate nervous system is composed of a wide range of neurons and complex synaptic connections, raising the intriguing question of how neuronal diversity is generated. The spinal cord provides an excellent model for exploring the mechanisms governing neuronal diversity due to its simple neural network and the conserved molecular processes involved in neuron formation and specification during evolution. This review specifically examines two distinct progenitor domains present in the zebrafish ventral spinal cord: the lateral floor plate (LFP) and the p2 progenitor domain. The LFP is responsible for the production of GABAergic Kolmer-Agduhr neurons (KA″), glutamatergic V3 neurons, and intraspinal serotonergic neurons, while the p2 domain generates V2 precursors that subsequently differentiate into three unique subpopulations of V2 neurons, namely glutamatergic V2a, GABAergic V2b, and glycinergic V2s. Based on recent findings, we will examine the fundamental signaling pathways and transcription factors that play a key role in the specification of these diverse neurons and neuronal subtypes derived from the LFP and p2 progenitor domains.

Ligand Mediation for Tunable and Oxide Suppressed Surface Gold-Decorated Liquid Metal Nanoparticles

Gallium-based liquid metal systems hold vast potential in materials science. However, maximizing their possibilities is hindered by gallium's native oxide and interfacial functionalization. In this study, small-molecule ligands are adopted as surfactants to modify the surface of eutectic gallium indium (EGaIn) nanoparticles and suppress oxidation. Different p-aniline derivatives are explored. Next, the reduction of chloroanric acid (HAuCl4 ) onto these p-aniline ligand modified EGaIn nanoparticles is investigated to produce gold-decorated EGaIn nanosystems. It is found that by altering the concentrations of HAuCl4 or the p-aniline ligand, the formation of gold nanoparticles (AuNPs) on EGaIn can be manipulated. The reduction of interfacial oxidation and presence of AuNPs enhances electrical conductivity, plasmonic performance, wettability, stability, and photothermal performance of all the p-aniline derivative modified EGaIn. Of these, EGaIn nanoparticles covered with the ligand of p-aminobenzoic acid offer the most evenly distributed AuNPs decoration and perfect elimination of gallium oxides, resulting in the augmented electrical conductivity, and highest wettability suitable for patterning, enhanced aqueous stability, and favorable photothermal properties. The proof-of-concept application in photothermal therapy of cancer cells demonstrates significantly enhanced photothermal conversion performance along with good biocompatibility. Due to such unique characteristics, the developed gold-decorated EGaIn nanodroplets are expected to offer significant potential in precise medicine.

Patterning ganglionic eminences in developing human brain organoids using a morphogen-gradient-inducing device

In early neurodevelopment, the central nervous system is established through the coordination of various neural organizers directing tissue patterning and cell differentiation. Better recapitulation of morphogen gradient production and signaling will be crucial for establishing improved developmental models of the brain in vitro. Here, we developed a method by assembling polydimethylsiloxane devices capable of generating a sustained chemical gradient to produce patterned brain organoids, which we termed morphogen-gradient-induced brain organoids (MIBOs). At 3.5 weeks, MIBOs replicated dorsal-ventral patterning observed in the ganglionic eminences (GE). Analysis of mature MIBOs through single-cell RNA sequencing revealed distinct dorsal GE-derived CALB2+ interneurons, medium spiny neurons, and medial GE-derived cell types. Finally, we demonstrate long-term culturing capabilities with MIBOs maintaining stable neural activity in cultures grown up to 5.5 months. MIBOs demonstrate a versatile approach for generating spatially patterned brain organoids for embryonic development and disease modeling.

Protein-Assisted Large-Scale Assembly and Differential Patterning of DNA Origami Lattices

Nanofabrication has experienced a big boost with the invention of DNA origami, enabling the production and assembly of complex nanoscale structures that may be able to unlock fully new functionalities in biology and beyond. The remarkable precision with which these structures can be designed and produced is, however, not yet matched by their assembly dynamics, which can be extremely slow, particularly when attached to biological templates, such as membranes. Here, the rapid and controlled formation of DNA origami lattices on the scale of hundreds of micrometers in as little as 30 minutes is demonstrated, utilizing active patterning by the E.coli Min protein system, thereby yielding a remarkable improvement over conventional passive diffusion-based assembly methods. Various patterns, including spots, inverse spots, mazes, and meshes can be produced at different scales, tailored through the shape and density of the assembled structures. The differential positioning accomplished by Min-induced diffusiophoresis even allows the introduction of "pseudo-colors", i.e., complex core-shell patterns, by simultaneously patterning different DNA origami species. Beyond the targeted functionalization of biological surfaces, this approach may also be promising for applications in plasmonics, catalysis, and molecular sensing.

Transparent Patternable Large-Area Graphene p-n Junctions by Photoinduced Electron Doping

We present a novel approach to achieve n-type doping in graphene and create graphene p-n junctions through a photoinduced electron doping method using photobase generators (PBGs). The unique properties of PBGs allow us to spatially and temporally control the doping process via light activation. The selective irradiation of specific regions on the graphene film enables switching their doping from p- to n-type, as confirmed by changes in the electromotive force and Seebeck and Hall coefficients. We demonstrate a stable (over 2 months) high electron mobility exceeding 1000 cm2 V-1s-1 using Hall effect measurements. The precise control of doping and the creation of p-n junctions in graphene offer exciting possibilities for various electronic, optoelectronic, and thermoelectric applications. Furthermore, we fabricate transparent graphene thermocouples with a high electromotive force of approximately ca. 80 μV/K, which validates the reliability and effectiveness of our approach for temperature sensing applications. This work paves the way for high-performance graphene-based electronic devices via controlled doping and patterning techniques. These findings provide valuable insights for the practical implementation of graphene in various fields.

Hierarchical Surface Pattern on Ni-Free Ti-Based Bulk Metallic Glass to Control Cell Interactions

Ni-free Ti-based bulk metallic glasses (BMGs) are exciting materials for biomedical applications because of their outstanding biocompatibility and advantageous mechanical properties. The glassy nature of BMGs allows them to be shaped and patterned via thermoplastic forming (TPF). This work demonstrates the versatility of the TPF technique to create micro- and nano-patterns and hierarchical structures on Ti40 Zr10 Cu34 Pd14 Sn2 BMG. Particularly, a hierarchical structure fabricated by a two-step TPF process integrates 400 nm hexagonal close-packed protrusions on 2.5 µm square protuberances while preserving the advantageous mechanical properties from the as-cast material state. The correlations between thermal history, structure, and mechanical properties are explored. Regarding biocompatibility, Ti40 Zr10 Cu34 Pd14 Sn2 BMGs with four surface topographies (flat, micro-patterned, nano-patterned, and hierarchical-structured surfaces) are investigated using Saos-2 cell lines. Alamar Blue assay and live/dead analysis show that all tested surfaces have good cell proliferation and viability. Patterned surfaces are observed to promote the formation of longer filopodia on the edge of the cytoskeleton, leading to star-shaped and dendritic cell morphologies compared with the flat surface. In addition to potential implant applications, TPF-patterned Ti-BMGs enable a high level of order and design flexibility on the surface topography, expanding the available toolbox for studying cell behavior on rigid and ordered surfaces.

Learning the mechanobiology of development from gastruloids

Gastruloids acquire their organization and shape through cell biochemical and mechanical activities. Such activities determine the physical forces and changes in material properties that transform simple spherical aggregates into organized tissues. In this Perspective, we discuss why the concepts and approaches of mechanobiology, a discipline that focuses on cell and tissue mechanics and its contribution to the organization and functions of living systems, are essential to the gastruloid field and, in turn, what gastruloids may teach us about mechanobiology.

Opposing, spatially-determined epigenetic forces impose restrictions on stochastic olfactory receptor choice

Olfactory receptor (OR) choice represents an example of genetically hardwired stochasticity, where every olfactory neuron expresses one out of ~2000 OR alleles in the mouse genome in a probabilistic, yet stereotypic fashion. Here, we propose that topographic restrictions in OR expression are established in neuronal progenitors by two opposing forces: polygenic transcription and genomic silencing, both of which are influenced by dorsoventral gradients of transcription factors NFIA, B, and X. Polygenic transcription of OR genes may define spatially constrained OR repertoires, among which one OR allele is selected for singular expression later in development. Heterochromatin assembly and genomic compartmentalization of OR alleles also vary across the axes of the olfactory epithelium and may preferentially eliminate ectopically expressed ORs with more dorsal expression destinations from this 'privileged' repertoire. Our experiments identify early transcription as a potential 'epigenetic' contributor to future developmental patterning and reveal how two spatially responsive probabilistic processes may act in concert to establish deterministic, precise, and reproducible territories of stochastic gene expression.

Protein-Based Patterning to Spatially Functionalize Biomimetic Membranes

The bottom-up reconstitution of proteins for their modular engineering into synthetic cellular systems can reveal hidden protein functions in vitro. This is particularly evident for the bacterial Min proteins, a paradigm for self-organizing reaction-diffusion systems that displays an unexpected functionality of potential interest for bioengineering: the directional active transport of any diffusible cargo molecule on membranes. Here, the MinDE protein system is reported as a versatile surface patterning tool for the rational design of synthetically assembled 3D systems. Employing two-photon lithography, microswimmer-like structures coated with tailored lipid bilayers are fabricated and demonstrate that Min proteins can uniformly pattern bioactive molecules on their surface. Moreover, it is shown that the MinDE system can form stationary patterns inside lipid vesicles, which allow the targeting and distinctive clustering of higher-order protein structures on their inner leaflet. Given their facile use and robust function, Min proteins thus constitute a valuable molecular toolkit for spatially patterned functionalization of artificial biosystems like cell mimics and microcarriers.

Fabrication of Silver Iodide (AgI) Patterns via Photolithography and Its Application to In-Situ Observation of Condensation Frosting

This study introduces an innovative photolithography-based method for patterning ionic and inorganic particle materials such as silver iodide (AgI). Conventional methods lack precision when patterning powdered materials, which limits their applicability. The proposed method stacks layers of a particle material (AgI) and negative-tone photoresist for simultaneous ultraviolet exposure and development, resulting in well-defined AgI patterns. The sintering process successfully removed binders from the material layer and photoresist, yielding standalone AgI patterns on the Si substrate with good adhesion. The pitch remained consistent with the design values of the photomask when the pattern size was changed. In-situ observation of condensation frosting on the patterns was conducted, which confirmed the practicality of the developed patterning process. This versatile method is applicable to large areas with a high throughput and presents new opportunities for modifying functional surfaces.

Neuroepithelial organoid patterning is mediated by a neighborhood watch mechanism

During epithelial tissue patterning, morphogens operate across multiple length scales to instruct cell identities. However, how cell fate changes are coordinated over these scales to establish spatial organization remains poorly understood. Here, we use human neural tube organoids as models of epithelial patterning and develop an in silico approach to define conditions permissive to patterning. By systematically varying morphogen position, diffusivity, and fate-inducing concentration levels, we show that cells follow a "neighborhood watch" (NW) mechanism that is deterministically dictated by initial morphogen source positions, reflecting scale-invariant in vitro phenotypes. We define how the frequency and local bias of morphogen sources stabilize pattern orientation. The model predicts enhanced patterning through floor plate inhibition, and receptor-ligand interaction analysis of single-cell RNA sequencing (scRNA-seq) data identifies wingless-related integration site (WNT) and bone morphogenic protein (BMP) as inhibition modulators, which we validate in vitro. These results suggest that developing neuroepithelia employ NW-based mechanisms to organize morphogen sources, define cellular identity, and establish patterns.

Microscopic Projection Lithography for Integrating Metallic Microstructures on Silk Protein for Biodevice Applications

Precise patterning of metallic micro/nanostructures enables application of silk protein in biomedical devices with a seamless human-machine interface. However, high-quality, expensive equipment and facilities involved in micro/nanofabrication hinder rapid prototyping for explorative laboratory-based research. Here, we report cost-effective and high-resolution light-emitting diode-based projection lithography methods for fabricating a Cr photomask and metallic microstructures on a silk protein layer. After two-step photolithography performed using a commercial camera and microscopic objective lens, inkjet-printed patterns are successfully projected on the silk layers with 100× and 500× demagnification ratios. A lift-off process is conducted to integrate Au patterns on the lithographic-patterned resist/silk layer, and various Au microstructures with sizes <2 μm are generated. In all the processes, the silk protein exhibits a high resistance to chemicals for resist solvent, development, resist strip, and lift-off, as well as a strong adhesion to gold, along with low cytotoxicity. Dopamine sensing and transistor operating capabilities are proved by measuring the changes in the electrical signals through the Au patterns. The proposed method is a cost-effective and simple approach for rapid prototyping of silk-based biomedical devices.

Progress and Prospects in Metallic FexGeTe2 (3 ≤ x ≤ 7) Ferromagnets

Thermal fluctuations in two-dimensional (2D) isotropy systems at non-zero finite temperatures can destroy the long-range (LR) magnetic order due to the mechanisms addressed in the Mermin-Wanger theory. However, the magnetic anisotropy related to spin-orbit coupling (SOC) may stabilize magnetic order in 2D systems. Very recently, 2D FexGeTe2 (3 ≤ x ≤ 7) with a high Curie temperature (TC) has not only undergone significant developments in terms of synthetic methods and the control of ferromagnetism (FM), but is also being actively explored for applications in various devices. In this review, we introduce six experimental methods, ten ferromagnetic modulation strategies, and four spintronic devices for 2D FexGeTe2 materials. In summary, we outline the challenges and potential research directions in this field.

The Arabidopsis SHORTROOT network coordinates shoot apical meristem development with auxin-dependent lateral organ initiation

Plants produce new organs post-embryonically throughout their entire life cycle. This is due to stem cells present in the shoot and root apical meristems, the SAM and RAM, respectively. In the SAM, stem cells are located in the central zone where they divide slowly. Stem cell daughters are displaced laterally and enter the peripheral zone, where their mitotic activity increases and lateral organ primordia are formed. How the spatial arrangement of these different domains is initiated and controlled during SAM growth and development, and how sites of lateral organ primordia are determined in the peripheral zone is not yet completely understood. We found that the SHORTROOT (SHR) transcription factor together with its target transcription factors SCARECROW (SCR), SCARECROW-LIKE23 (SCL23) and JACKDAW (JKD), promotes formation of lateral organs and controls shoot meristem size. SHR, SCR, SCL23, and JKD are expressed in distinct, but partially overlapping patterns in the SAM. They can physically interact and activate expression of key cell cycle regulators such as CYCLIND6;1 (CYCD6;1) to promote the formation of new cell layers. In the peripheral zone, auxin accumulates at sites of lateral organ primordia initiation and activates SHR expression via the auxin response factor MONOPTEROS (MP) and auxin response elements in the SHR promoter. In the central zone, the SHR-target SCL23 physically interacts with the key stem cell regulator WUSCHEL (WUS) to promote stem cell fate. Both SCL23 and WUS expression are subject to negative feedback regulation from stem cells through the CLAVATA signaling pathway. Together, our findings illustrate how SHR-dependent transcription factor complexes act in different domains of the shoot meristem to mediate cell division and auxin dependent organ initiation in the peripheral zone, and coordinate this activity with stem cell maintenance in the central zone of the SAM.

Patterning Quantum Dots via Photolithography: A Review

Pixelating patterns of red, green, and blue quantum dots (QDs) is a critical challenge for realizing high-end displays with bright and vivid images for virtual, augmented, and mixed reality. Since QDs must be processed from a solution, their patterning process is completely different from the conventional techniques used in the organic light-emitting diode and liquid crystal display industries. Although innovative QD patterning technologies are being developed, photopatterning based on the light-induced chemical conversion of QD films is considered one of the most promising methods for forming micrometer-scale QD patterns that satisfy the precision and fidelity required for commercialization. Moreover, the practical impact will be significant as it directly exploits mature photolithography technologies and facilities that are widely available in the semiconductor industry. This article reviews recent progress in the effort to form QD patterns via photolithography. The review begins with a general description of the photolithography process. Subsequently, different types of photolithographical methods applicable to QD patterning are introduced, followed by recent achievements using these methods in forming high-resolution QD patterns. The paper also discusses prospects for future research directions.

Different Roles of Surface Chemistry and Roughness of Laser-Induced Graphene: Implications for Tunable Wettability

The control of surface wettability is a technological key aspect and usually poses considerable challenges connected to high cost, nanostructure, and durability, especially when aiming at surface patterning with high and extreme wettability contrast. This work shows a simple and scalable approach by using laser-induced graphene (LIG) and a locally inert atmosphere to continuously tune the wettability of a polyimide/LIG surface from hydrophilic to superhydrophobic (Φ ∼ 160°). This is related to the reduced amount of oxygen on the LIG surface, influenced by the local atmosphere. Furthermore, the influence of the roughness pattern of LIG on the wettability is investigated. Both approaches are combined, and the influence of surface chemistry and roughness is discussed. Measurements of the roll-off angle show that LIG scribed in an inert atmosphere with a low roughness has the highest droplet mobility with a roll-off angle of ΦRO = (1.7 ± 0.3)°. The superhydrophobic properties of the samples were maintained for over a year and showed no degradation after multiple uses. Applications of surfaces with extreme wettability contrast in millifluidics and fog basking are demonstrated. Overall, the proposed processing allows for the continuous tuning and patterning of the surface properties of LIG in a very accessible fashion useful for "lab-on-chip" applications.

Quantum Transport in Large-Scale Patterned Nitrogen-Doped Graphene

It has recently been demonstrated how the nitrogen dopant concentration in graphene can be controlled spatially on the nano-meter scale using a molecular mask. This technique may be used to create ballistic electron optics-like structures of high/low doping regions; for example, to focus electron beams, harnessing the quantum wave nature of the electronic propagation. Here, we employ large-scale Greens function transport calculations based on a tight-binding approach. We first benchmark different tight-binding models of nitrogen in graphene with parameters based on density functional theory (DFT) and the virtual crystal approximation (VCA). Then, we study theoretically how the random distribution within the masked regions and the discreteness of the nitrogen scattering centers impact the transport behavior of sharp n-p and n-n' interfaces formed by different, realistic nitrogen concentrations. We investigate how constrictions for the current can be realized by patterned high/low doping regions with experimentally feasible nitrogen concentrations. The constrictions can guide the electronic current, while the quantized conductance is significantly washed out due to the nitrogen scattering. The implications for device design is that a p-n junction with nitrogen corrugation should still be viable for current focusing. Furthermore, a guiding channel with less nitrogen in the conducting canal preserves more features of quantized conductance and, therefore, its low-noise regime.

Arabidopsis TCP4 transcription factor inhibits high temperature-induced homeotic conversion of ovules

Abnormal high temperature (HT) caused by global warming threatens plant survival and food security, but the effects of HT on plant organ identity are elusive. Here, we show that Class II TEOSINTE BRANCHED 1/CYCLOIDEA/ PCF (TCP) transcription factors redundantly protect ovule identity under HT. The duodecuple tcp2/3/4/5/10/13/17/24/1/12/18/16 (tcpDUO) mutant displays HT-induced ovule conversion into carpelloid structures. Expression of TCP4 in tcpDUO complements the ovule identity conversion. TCP4 interacts with AGAMOUS (AG), SEPALLATA3 (SEP3), and the homeodomain transcription factor BELL1 (BEL1) to strengthen the association of BEL1 with AG-SEP3. The tcpDUO mutant synergistically interacts with bel1 and the ovule identity gene seedstick (STK) mutant stk in tcpDUO bel1 and tcpDUO stk. Our findings reveal the critical roles of Class II TCPs in maintaining ovule identity under HT and shed light on the molecular mechanisms by which ovule identity is determined by the integration of internal factors and environmental temperature.

Is Drosophila Dpp/BMP morphogen spreading required for wing patterning and growth?

Secreted signaling molecules act as morphogens to control patterning and growth in many developing tissues. Since locally produced morphogens spread to form a concentration gradient in the surrounding tissue, spreading is generally thought to be the key step in the non-autonomous actions. Here, we review recent advances in tool development to investigate morphogen function using the role of decapentaplegic (Dpp)/bone morphogenetic protein (BMP)-type ligand in the Drosophila wing disc as an example. By applying protein binder tools to distinguish between the roles of Dpp spreading and local Dpp signaling, we found that Dpp signaling in the source cells is important for wing patterning and growth but Dpp spreading from this source cells is not as strictly required as previously thought. Given recent studies showing unexpected requirements of long-range action of different morphogens, manipulating endogenous morphogen gradients by synthetic protein binder tools could shed more light on how morphogens act in developing tissues.

A Novel Perspective on Neuronal Control of Anatomical Patterning, Remodeling, and Maintenance

While the nervous system may be best known as the sensory communication center of an organism, recent research has revealed a myriad of multifaceted roles for both the CNS and PNS from early development to adult regeneration and remodeling. These systems work to orchestrate tissue pattern formation during embryonic development and continue shaping pattering through transitional periods such as metamorphosis and growth. During periods of injury or wounding, the nervous system has also been shown to influence remodeling and wound healing. The neuronal mechanisms responsible for these events are largely conserved across species, suggesting this evidence may be important in understanding and resolving many human defects and diseases. By unraveling these diverse roles, this paper highlights the necessity of broadening our perspective on the nervous system beyond its conventional functions. A comprehensive understanding of the complex interactions and contributions of the nervous system throughout development and adulthood has the potential to revolutionize therapeutic strategies and open new avenues for regenerative medicine and tissue engineering. This review highlights an important role for the nervous system during the patterning and maintenance of complex tissues and provides a potential avenue for advancing biomedical applications.

Dynamic Fusion of Nucleic Acid Functionalized Nano-/Micro-Cell-Like Containments: From Basic Concepts to Applications

Membrane fusion processes play key roles in biological transformations, such as endocytosis/exocytosis, signal transduction, neurotransmission, or viral infections, and substantial research efforts have been directed to emulate these functions by artificial means. The recognition and dynamic reconfiguration properties of nucleic acids provide a versatile means to induce membrane fusion. Here we address recent advances in the functionalization of liposomes or membranes with structurally engineered lipidated nucleic acids guiding the fusion of cell-like containments, and the biophysical and chemical parameters controlling the fusion of the liposomes will be discussed. Intermembrane bridging by duplex or triplex nucleic acids and light-induced activation of membrane-associated nucleic acid constituents provide the means for spatiotemporal fusion of liposomes or nucleic acid modified liposome fusion with native cell membranes. The membrane fusion processes lead to exchange of loads in the fused containments and are a means to integrate functional assemblies. This is exemplified with the operation of biocatalytic cascades and dynamic DNA polymerization/nicking or transcription machineries in fused protocell systems. Membrane fusion processes of protocell assemblies are found to have important drug-delivery, therapeutic, sensing, and biocatalytic applications. The future challenges and perspectives of DNA-guided fused containments and membranes are addressed.

A BLADE-ON-PETIOLE orthologue regulates corolla differentiation in the proximal region in Torenia fournieri

The three-dimensional shape of a flower is integrated by morphogenesis along different axes. Differentiation along the petal proximodistal axis is tightly linked to the specification of pollinators; however, it is still unclear how a petal patterns this axis. The corolla of Torenia fournieri exhibits strong differentiation along the proximodistal axis, and we previously found a proximal regulator, TfALOG3, controlling corolla neck differentiation. Here, we report another gene, TfBOP2, which is predominantly expressed in the proximal region of the corolla. TfBOP2 mutants have shorter proximal corolla tubes and longer distal lobe, demonstrating its function as a proximal regulator. Arabidopsis BOPs mutant shows similar defects, favouring a shared role of BOPs homologues. Genetic analysis demonstrates the interaction between TfBOP2 and TfALOG3, and we further found that TfALOG3 physically interacts with TfBOP2 and can recruit TfBOP2 to the nuclear region. Our study favours a hypothetical shared BOP-ALOG complex that is recruited to regulate corolla differentiation in the proximal region axis of T. fournieri.

Nanocrystal Array Engineering and Optoelectronic Applications of Organic Small-Molecule Semiconductors

Organic small-molecule semiconductor materials have attracted extensive attention because of their excellent properties. Due to the randomness of crystal orientation and growth location, however, the preparation of continuous and highly ordered organic small-molecule semiconductor nanocrystal arrays still face more challenges. Compared to organic macromolecules, organic small molecules exhibit better crystallinity, and therefore, they exhibit better semiconductor performance. The formation of organic small-molecule crystals relies heavily on weak interactions such as hydrogen bonds, van der Waals forces, and π-π interactions, which are very sensitive to external stimuli such as mechanical forces, high temperatures, and organic solvents. Therefore, nanocrystal array engineering is more flexible than that of the inorganic materials. In addition, nanocrystal array engineering is a key step towards practical application. To resolve this problem, many conventional nanocrystal array preparation methods have been developed, such as spin coating, etc. In this review, the typical and recent progress of nanocrystal array engineering are summarized. It is the typical and recent innovations that the array of nanocrystal array engineering can be patterned on the substrate through top-down, bottom-up, self-assembly, and crystallization methods, and it can also be patterned by constructing a series of microscopic structures. Finally, various multifunctional and emerging applications based on organic small-molecule semiconductor nanocrystal arrays are introduced.

Direct Optical Patterning of Quantum Dots: One Strategy, Different Chemical Processes

Patterning, stability, and dispersion of the semiconductor quantum dots (scQDs) are three issues strictly interconnected for successful device manufacturing. Recently, several authors adopted direct optical patterning (DOP) as a step forward in photolithography to position the scQDs in a selected area. However, the chemistry behind the stability, dispersion, and patterning has to be carefully integrated to obtain a functional commercial device. This review describes different chemical strategies suitable to stabilize the scQDs both at a single level and as an ensemble. Special attention is paid to those strategies compatible with direct optical patterning (DOP). With the same purpose, the scQDs' dispersion in a matrix was described in terms of the scQD surface ligands' interactions with the matrix itself. The chemical processes behind the DOP are illustrated and discussed for five different approaches, all together considering stability, dispersion, and the patterning itself of the scQDs.

Direct synthesis of nanopatterned epitaxial graphene on silicon carbide

This article introduces a straightforward approach for the direct synthesis of transfer-free, nanopatterned epitaxial graphene on silicon carbide on silicon substrates. A catalytic alloy tailored to optimal SiC graphitization is pre-patterned with common lithography and lift-off techniques to form planar graphene structures on top of an unpatterned SiC layer. &#xD;This method is compatible with both electron-beam lithography and UV-lithography, and graphene gratings down to at least ~100 nm width/space can be realized at the wafer scale. The minimum pitch is limited by the flow of the metal catalyst during the liquid-phase graphitization process. We expect that the current pitch resolution could be further improved by optimizing the metal deposition method and lift-off process.&#xD.

Pattern variation is linked to anti-predator coloration in butterfly larvae

Prey animals typically try to avoid being detected and/or advertise to would-be predators that they should be avoided. Both anti-predator strategies primarily rely on colour to succeed, but the specific patterning used is also important. While the role of patterning in camouflage is relatively clear, the design features of aposematic patterns are less well understood. Here, we use a comparative approach to investigate how pattern use varies across a phylogeny of 268 species of cryptic and aposematic butterfly larvae, which also vary in social behaviour. We find that longitudinal stripes are used more frequently by cryptic larvae, and that patterns putatively linked to crypsis are more likely to be used by solitary larvae. By contrast, aposematic larvae are more likely to use horizontal bands and spots, but we find no differences in the use of individual pattern elements between solitary and gregarious aposematic species. However, solitary aposematic larvae are more likely to display multiple pattern elements, whereas those with no pattern are more likely to be gregarious. Our study advances our understanding of how pattern variation, coloration and social behaviour covary across lepidopteran larvae, and highlights new questions about how patterning affects larval detectability and predator responses to aposematic prey.

A spatiotemporal barrier formed by Follistatin is required for left-right patterning

How left-right (LR) asymmetry emerges in a patterning field along the anterior-posterior axis remains an unresolved problem in developmental biology. Left-biased Nodal emanating from the LR organizer propagates from posterior to anterior (PA) and establishes the LR pattern of the whole embryo. However, little is known about the regulatory mechanism of the PA spread of Nodal and its asymmetric activation in the forebrain. Here, we identify bilaterally expressed Follistatin (Fst) as a regulator blocking the propagation of the zebrafish Nodal ortholog Southpaw (Spaw) in the right lateral plate mesoderm (LPM), and restricting Spaw transmission in the left LPM to facilitate the establishment of a robust LR asymmetric Nodal patterning. In addition, Fst inhibits the Activin-Nodal signaling pathway in the forebrain thus preventing Nodal activation prior to the arrival, at a later time, of Spaw emanating from the left LPM. This contributes to the orderly propagation of asymmetric Nodal activation along the PA axis. The LR regulation function of Fst is further confirmed in chick and frog embryos. Overall, our results suggest that a robust LR patterning emerges by counteracting a Fst barrier formed along the PA axis.

The Midbrain Preisthmus: A Poorly Known Effect of the Isthmic Organizer

This essay reexamines molecular evidence supporting the existence of the 'preisthmus', a caudal midbrain domain present in vertebrates (studied here in the mouse). It is thought to derive from the embryonic m2 mesomere and appears intercalated between the isthmus (caudally) and the inferior colliculus (rostrally). Among a substantial list of gene expression mappings examined from the Allen Developing and Adult Brain Atlases, a number of quite consistent selective positive markers, plus some neatly negative markers, were followed across embryonic stages E11.5, E13.5, E15.5, E18.5, and several postnatal stages up to the adult brain. Both alar and basal subdomains of this transverse territory were explored and illustrated. It is argued that the peculiar molecular and structural profile of the preisthmus is due to its position as rostrally adjacent to the isthmic organizer, where high levels of both FGF8 and WNT1 morphogens must exist at early embryonic stages. Isthmic patterning of the midbrain is discussed in this context. Studies of the effects of the isthmic morphogens usually do not attend to the largely unknown preisthmic complex. The adult alar derivatives of the preisthmus were confirmed to comprise a specific preisthmic sector of the periaqueductal gray, an intermediate stratum represented by the classic cuneiform nucleus, and a superficial stratum containing the subbrachial nucleus. The basal derivatives, occupying a narrow retrorubral domain intercalated between the oculomotor and trochlear motor nuclei, include dopaminergic and serotonergic neurons, as well as a variety of peptidergic neuron types.

Flexible Transparent Electrodes Formed from Template-Patterned Thin-Film Silver

We report template-patterned, flexible Transparent Electrodes (TEs) formed from an ultrathin silver film on top of a commercial optical adhesive - Norland Optical Adhesive 63 (NOA63). NOA63 is shown to be an effective base-layer for ultrathin silver films that advantageously prevents coalescence of vapour-deposited silver atoms into large, isolated islands (Volmer-Weber growth), and so aids the formation of ultrasmooth continuous films. 12-nm silver films on top of free-standing NOA63 combine high, haze-free visible-light transparency (T ≈ 60% at 550 nm) with low sheet-resistance ( R s ${\mathcal{R}}_s$ ≈ 16 Ω/sq.), and exhibit excellent resilience to bending, making them attractive candidates for flexible TEs. Etching the NOA63 base-layer with an oxygen plasma before silver deposition causes the silver to laterally segregate into isolated pillars, resulting in a much higher sheet resistance than silver grown on pristine NOA63 ( R s ${\mathcal{R}}_s$  > 8 × 10⁶  Ω/sq.). Hence, by selectively etching NOA63 before metal deposition, insulating regions may be defined within an otherwise conducting silver film, resulting in a differentially conductive film that can serve as a patterned TE for flexible devices. Transmittance may be increased (to 79% at 550 nm) by depositing an antireflective layer of Al₂ O₃ on the Ag layer at the cost of reduced flexibility. This article is protected by copyright. All rights reserved.

Patterning of Hydrophilic and Hydrophobic Gold and Magnetite Nanoparticles by Dip Pen Nanolithography

Nanoparticles offer unique physical and chemical properties. Dip pen nanolithography of nanoparticles enables versatile patterning and nanofabrication with potential application in electronics and sensing, but is not well studied yet. Herein, the patterned deposition of various nanoparticles onto unmodified silicon substrates is presented. It is shown that aqueous solutions of hydrophilic citrate and cyclodextrin functionalized gold nanoparticles as well as poly(acrylic) acid decorated magnetite nanoparticles are feasible for writing nanostructures. Both smaller and larger nanoparticles can be patterned. Hydrophobic oleylamine or n-dodecylamine capped gold nanoparticles and oleic acid decorated magnetite nanoparticles are deposited from toluene. Tip loading is carried out by dip-coating, and writing succeeds fast within 0.1 s. Also, coating with longer tip dwell times, at different relative humidity and varying frequency are studied for deposition of nanoparticle clusters. The resulting feature size is between 300 and 1780 nm as determined by scanning electron microscopy. Atomic force microscopy confirms that the heights of the deposited structures correspond to a single or double layer of nanoparticles. Higher writing speeds lead to smaller line thicknesses, offering possibilities to more complex structures. Dip pen nanolithography can hence be used to pattern nanoparticles on silicon substrates independent of the surface chemistry.

Shaping a Soft Future: Patterning Liquid Metals

This review highlights the unique techniques for patterning liquid metals containing gallium (e.g., eutectic gallium indium, EGaIn). These techniques are enabled by two unique attributes of these liquids relative to solid metals: 1) The fluidity of the metal allows it to be injected, sprayed, and generally dispensed. 2) The solid native oxide shell allows the metal to adhere to surfaces and be shaped in ways that would normally be prohibited due to surface tension. The ability to shape liquid metals into non-spherical structures such as wires, antennas, and electrodes can enable fluidic metallic conductors for stretchable electronics, soft robotics, e-skins, and wearables. The key properties of these metals with a focus on methods to pattern liquid metals into soft or stretchable devices are summari.

High-Resolution Patterning of Perovskite Quantum Dots via Femtosecond Laser-Induced Forward Transfer

High-resolution patterning of perovskite quantum dots (PQDs) is of significant importance for satisfying various practical applications, including high-resolution displays and image sensing. However, due to the limitation of the instability of PQDs, the existing patterning strategy always involves chemical reagent treatment or mask contact that is not suitable for PQDs. Therefore, it is still a challenge to fabricate high-resolution full-color PQD arrays. Here, we present a femtosecond laser-induced forward transfer (FsLIFT) technology, which enables the programmable fabrication of high-resolution full-color PQD arrays and arbitrary micropatterns. The FsLIFT process integrates transfer, deposition, patterning, and alignment in one step without involving a mask and chemical reagent treatment, guaranteeing the preservation of the photophysical properties of PQDs. A full-color PQD array with a high resolution of 2 μm has been successfully achieved. We anticipate that our facile and flexible FsLIFT technology can facilitate the development of diverse practical applications based on patterned PQDs.

Netrin-1 directs vascular patterning and maturity in the developing kidney

Blood filtering by the kidney requires the establishment of an intricate vascular system that works to support body fluid and organ homeostasis. Despite these critical roles, little is known about how vascular architecture is established during kidney development. More specifically, how signals from the kidney influence vessel maturity and patterning remains poorly understood. Netrin-1 (Ntn1) is a secreted ligand critical for vessel and neuronal guidance. Here, we demonstrate that Ntn1 is expressed by stromal progenitors in the developing kidney, and conditional deletion of Ntn1 from Foxd1+ stromal progenitors (Foxd1GC/+;Ntn1fl/fl) results in hypoplastic kidneys that display extended nephrogenesis. Despite expression of the netrin-1 receptor Unc5c in the adjacent nephron progenitor niche, Unc5c knockout kidneys develop normally. The netrin-1 receptor Unc5b is expressed by embryonic kidney endothelium and therefore we interrogated the vascular networks of Foxd1GC/+;Ntn1fl/fl kidneys. Wholemount, 3D analyses revealed the loss of a predictable vascular pattern in mutant kidneys. As vascular patterning has been linked to vessel maturity, we investigated arterialization in these mutants. Quantification of the CD31+ endothelium at E15.5 revealed no differences in metrics such as the number of branches or branch points, whereas the arterial vascular smooth muscle metrics were significantly reduced at both E15.5 and P0. In support of these results, whole kidney RNA-seq showed upregulation of angiogenic programs and downregulation of muscle-related programs which included smooth muscle-associated genes. Together, our findings highlight the significance of netrin-1 to proper vascularization and kidney development.

Bioelectricity in Developmental Patterning and Size Control: Evidence and Genetically Encoded Tools in the Zebrafish Model

Developmental patterning is essential for regulating cellular events such as axial patterning, segmentation, tissue formation, and organ size determination during embryogenesis. Understanding the patterning mechanisms remains a central challenge and fundamental interest in developmental biology. Ion-channel-regulated bioelectric signals have emerged as a player of the patterning mechanism, which may interact with morphogens. Evidence from multiple model organisms reveals the roles of bioelectricity in embryonic development, regeneration, and cancers. The Zebrafish model is the second most used vertebrate model, next to the mouse model. The zebrafish model has great potential for elucidating the functions of bioelectricity due to many advantages such as external development, transparent early embryogenesis, and tractable genetics. Here, we review genetic evidence from zebrafish mutants with fin-size and pigment changes related to ion channels and bioelectricity. In addition, we review the cell membrane voltage reporting and chemogenetic tools that have already been used or have great potential to be implemented in zebrafish models. Finally, new perspectives and opportunities for bioelectricity research with zebrafish are discussed.

Patterning Perovskite Quantum Dots Using Photopolymerization

All-inorganic cesium lead halide perovskite quantum dots (QDs) have several potential applications, owing to their unique optical and electronic properties. However, patterning perovskite QDs using conventional methods is difficult because of the ionic nature of QDs. Here, we demonstrate a unique approach, in which perovskite QDs are patterned in polymer films through the photocuring of monomers under patterned light illumination. The pattern illumination creates the transient polymer concentration difference, which drives the QDs to form patterns; hence controlling polymerization kinetics is essential for the generation of the QD pattern. For the patterning mechanism, a light projection system equipped with a digital micromirror device (DMD) is developed; thus, light intensity, an important factor to determine polymerization kinetics, is precisely controlled per position on the photocurable solution, resulting in the understanding of the mechanism and the formation of distinct QD patterns. The demonstrated approach assisted by the DMD-equipped projection system can form desired perovskite QD patterns solely by patterned light illumination, paving the way for the development of patterning methods for perovskite QDs and other nanocrystals.

Pattern dynamics and stochasticity of the brain rhythms

Our current understanding of brain rhythms is based on quantifying their instantaneous or time-averaged characteristics. What remains unexplored is the actual structure of the waves-their shapes and patterns over finite timescales. Here, we study brain wave patterning in different physiological contexts using two independent approaches: The first is based on quantifying stochasticity relative to the underlying mean behavior, and the second assesses "orderliness" of the waves' features. The corresponding measures capture the waves' characteristics and abnormal behaviors, such as atypical periodicity or excessive clustering, and demonstrate coupling between the patterns' dynamics and the animal's location, speed, and acceleration. Specifically, we studied patterns of θ, γ, and ripple waves recorded in mice hippocampi and observed speed-modulated changes of the wave's cadence, an antiphase relationship between orderliness and acceleration, as well as spatial selectiveness of patterns. Taken together, our results offer a complementary-mesoscale-perspective on brain wave structure, dynamics, and functionality.

Engineering Multi-Scale Organization for Biotic and Organic Abiotic Electroactive Systems

Multi-scale organization of molecular and living components is one of the most critical parameters that regulate charge transport in electroactive systems-whether abiotic, biotic, or hybrid interfaces. In this article, an overview of the current state-of-the-art for controlling molecular order, nanoscale assembly, microstructure domains, and macroscale architectures of electroactive organic interfaces used for biomedical applications is provided. Discussed herein are the leading strategies and challenges to date for engineering the multi-scale organization of electroactive organic materials, including biomolecule-based materials, synthetic conjugated molecules, polymers, and their biohybrid analogs. Importantly, this review provides a unique discussion on how the dependence of conduction phenomena on structural organization is observed for electroactive organic materials, as well as for their living counterparts in electrogenic tissues and biotic-abiotic interfaces. Expansion of fabrication capabilities that enable higher resolution and throughput for the engineering of ordered, patterned, and architecture electroactive systems will significantly impact the future of bioelectronic technologies for medical devices, bioinspired harvesting platforms, and in vitro models of electroactive tissues. In summary, this article presents how ordering at multiple scales is important for modulating transport in both the electroactive organic, abiotic, and living components of bioelectronic systems.