Microscale Patterns Research Articles

Tunable Light-Actuated Interpenetrating Networks of Silk Fibroin and Gelatin for Tissue Engineering and Flexible Biodevices.

Soft materials with tunable properties are valuable for applications such as tissue engineering, electronic skins, and human-machine interfaces. Materials that are nature-derived offer additional advantages such as biocompatibility, biodegradability, low-cost sourcing, and sustainability. However, these materials often have contrasting properties that limit their use. For example, silk fibroin (SF) has high mechanical strength but lacks processability and cell-adhesive domains. Gelatin, derived from collagen, has excellent biological properties, but is fragile and lacks stability. To overcome these limitations, composites of gelatin and SF have been explored. However, mechanically robust self-supported matrices and electrochemically active or micropatterned substrates were not demonstrated. In this study, we present a composite of photopolymerizable SF and photogelatin, termed photofibrogel (PFG). By incorporating photoreactive properties in both SF and gelatin, control over material properties can be achieved. The PFG composite can be easily and rapidly formed into free-standing, high-resolution architectures with tunable properties. By optimizing the ratio of SF to gelatin, properties such as swelling, mechanical behavior, enzymatic degradation, and patternability are tailored. The PFG composite allows for macroscale and microscale patterning without significant swelling, enabling the fabrication of structures using photolithography and laser cutting techniques. PFG can be patterned with electrically conductive materials, making it suitable for cell guidance and stimulation. The versatility, mechanical robustness, bioactivity, and electrochemical properties of PFG are shown for skeletal muscle tissue engineering using C2C12 cells as a model. Overall, such composite biomaterials with tunable properties have broad potential in flexible bioelectronics, wound healing, regenerative medicine, and food systems.

Dynamic Color-Switching of Hydrogel Micropillar Array under Ethanol Vapor for Optical Encryption.

Responsive structural colors from artificially engineered micro/nanostructures are critical to the development of anti-counterfeiting, optical encryption, and intelligent display. Herein, the responsive structural color of hydrogel micropillar array is demonstrated under the external stimulus of ethanol vapor. Micropillar arrays with full color are fabricated via femtosecond laser direct writing by controlling the height and diameter of the micropillars according to the FDTD simulation. Color-switching of the micropillar arrays is achieved in <1s due to the formation of liquid film among micropillars. More importantly, the structural color blueshift of the micropillar arrays is sensitive to the micropillar diameter, instead of the micropillar height. The micropillar array with a diameter of 772nm takes 400ms to complete blueshift under ethanol vapor, while that with a diameter of 522nm blueshifts at 2400ms. Microscale patterns are realized by employing the size-dependent color-switching of designed micropillar arrays under ethanol vapor. Moreover, Morse code and directional blueshift of structural colors are realized in the micropillar arrays. The advantages of controllable color-switching of the hydrogel micropillar array would be prospective in the areas of optical encryption, dynamic display, and anti-counterfeiting.

The structure of microbial communities in redoximorphic microsites of Gleysol

AbstractMicrobial communities were studied in redoximorphic microsites of highly heterogeneous Gleysol at a mm scale using 16S and 18S amplicon sequencing to demonstrate if the composition of soil microbes reflects the differences in ferric and ferrous micro‐sites. In both explored gley horizons with redoximorphic features (Bg2 and Cg), ferric mottles were significantly enriched with total P and Fe and depleted of O, Si, Al, K and Ca compared with the adjacent ferrous groundmass (SEM–EDS). Ferric mottles were determined as Fe oxide coatings and hypocoatings. In Bg2, both prokaryotic and micro‐eukaryotic communities differed significantly between mottles and groundmass in composition of operational taxonomic units (OTUs) and in proportions of phyla, reflecting heterogeneities in the soil properties there. Mottles in Bg2 were characterized by increased proportion of Proteobacteria, decreased proportion of Acidobacteriota among prokaryotes and by dominance of a single proteobacterial OTU from Anaplasmataceae compared to all other samples. The composition of micro‐eukaryotes showed an opposite trend, as micro‐eukaryotes of Bg2 groundmass were unique among the other horizons, while micro‐eukaryotes of Bg2 mottles had similar composition to neighbouring horizons. Microbial communities of adjacent samples were not more similar to each other than communities of randomly selected ones in Bg2 horizon. That suggests that at mm scale, the sample distance does not represent the driving factor of microbial community composition and that the adjacent samples differ rather due to physicochemical factors. The spatial organization of microbial communities revealed in Bg2 has not reappeared in similarly organized Cg horizon, probably due to other overriding factors. The differences revealed between Bg2 and Cg horizons, including granulometric composition, content of crystalline Fe, exchangeable Al, and organic carbon, as well as exposition to groundwater, were discussed as possible reasons of the distinct organization in Cg. The similarity of pro−/eukaryotic communities of adjacent and non‐adjacent couples suggests no distance decay pattern at a mm scale. The agreement between patchiness in soil properties and microbial communities was revealed for the first time and confirms the importance of microscale patterns in soil.

Spatiotemporal localisation patterns of technological startups: the case for recurrent neural networks in predicting urban startup clusters

AbstractMore attention should be dedicated to intra-urban localisation decisions of technological startups. While the general trend of innovative companies being attracted to metropolitan areas is well-known and thoroughly researched, much less is understood about the micro-geographical patterns emerging within cities. Considering the growing number of papers mentioning that agglomeration externalities attenuate sharply with distance, such an analysis of micro-scale localisation patterns is crucial for understanding whether these effects are of importance for technological startups. Using a sample of startups from the up-and-coming market in Central-East Europe in Warsaw, Poland, their spatial organisation across the years will be tracked to investigate whether there is a defined pattern consistent with highly localised externalities operating within cities and how this pattern evolves over time. Additionally, the paper will show how recurrent neural networks may help predict the locations of technological startup clusters. It will be presented how to include the spatial dimension in the model in a computationally effective way and how this augmentation improves the results by allowing the network to “understand” the spatial relations between neighbouring observations.

3D-printing bionic-patterned zirconia via stereolithography promotes soft tissue integration for ceramic implants

Due to the desirable aesthetic performance, zirconia abutments attract tremendous attention in implant related restoration of the anterior zone. However, the inadequate soft tissue integration originated from the inertia surface of zirconia severely limits its application. Fabricating bionic-patterned zirconia abutments is believed to be a promising strategy to solve this puzzle. The main obstacle to fabricating bionic-pattern lies in that conventional zirconia manufacturing technology cannot precisely engineer complex micro-pattern. Notably, modern 3D printing presents a feasible way to obtain various sophisticated topological architecture. In the present study, series of bionic-patterned zirconia were fabricated by 3D printing, simulating lotus leaf, butterfly wings, shark skin, and gecko foot. The features of micro-patterns and quality of 3D printing were systematically characterized. In addition, the effect of various bionic-patterned zirconia on the behaviors of gingival fibroblasts was investigated. Results showed that zirconia with various micro-scale bionic patterns was successfully and precisely fabricated by 3D printing. Among the four types of bionic patterns, the ones that resembled the geckos’ feet or lotus leaves were the most recommended topography for cell growth and spreading, while the pattern mimicked shark skin upgraded the expression of fibroblast functional genes including Col-I, Fn, and Itgb-1 most obviously. The bionic-patterned zirconia can efficiently promote adhesion, proliferation, and related gene expression of gingival fibroblasts, indicating that bionic-patterned zirconia has great potential to promote soft tissue integration.

Fabrication of Nonconductive Microscale Patterns on Ion Exchange Membrane by Laser Process

The electroconvection generated on the surface of an ion exchange membrane (IEM) is closely related to the electrical/chemical characteristics or topology of the IEM. In particular, when non-conductive regions are mixed on the surface of the IEM, it can have a great influence on the transfer of ions and the formation of nonlinear electroconvective vortices, so more theoretical and experimental studies are necessary. Here, we present a novel method for creating microscale non-conductive patterns on the IEM surface by laser ablation, and successfully visualize microscale vortices on the surface modified IEM. Microscale (~300 µm) patterns were fabricated by applying UV nanosecond laser processing to the non-conductive film, and were transferred to the surface of the IEM. In addition, UV nanosecond laser process parameters were investigated for obvious micro-pattern production, and operating conditions were optimized, such as minimizing the heat-affected zone. Through this study, we found that non-conductive patterns on the IEM surface could affect the generation and growth of electroconvective vortices. The experimental results provided in our study are expected to be a good reference for research related to the surface modification of IEMs, and are expected to be helpful for new engineering applications of electroconvective vortices using a non-conductive patterned IEM.

Spatial heterogeneity of household water insecurity in rural Uganda: implications for development

ABSTRACT Little is known about the micro-scale spatial patterns of household water insecurity and their implications for community water interventions. This cross-sectional study analyses the location data of 250 households surveyed in Arua, Uganda, in August–September 2017 to evaluate correlates and geospatial clustering of household water insecurity, that is, geographical patterns in how water insecurity is experienced. The spatial cluster analysis identified clusters or outliers in every community, though with different spatial patterns. Household water insecurity was positively associated with food insecurity, round-trip fetching time, and water-related conflict within households and with neighbours. The observed spatial heterogeneity provides a new view of how household water insecurity experiences may vary in space and time, and can help practitioners understand the heterogeneity of impact that is often observed in water interventions.

Multi-dimensional dynamic fluorescence readout from laser engineered In2O3 nanowire micropatterns

A laser-irradiated array of In2O3 nanowires presents yellow and blue fluorescence states that can be dynamically altered under UV light for anti-counterfeiting features based upon microscale patterning, color evolution and time-domain encoding.

Moving through a changing world: Single cell migration in 2D vs. 3D.

Migration of single adherent cells is frequently observed in the developing and adult organism and has been the subject of many studies. Yet, while elegant work has elucidated molecular and mechanical cues affecting motion dynamics on a flat surface, it remains less clear how cells migrate in a 3D setting. In this review, we explore the changing parameters encountered by cells navigating through a 3D microenvironment compared to cells crawling on top of a 2D surface, and how these differences alter subcellular structures required for propulsion. We further discuss how such changes at the micro-scale impact motion pattern at the macro-scale.

Micro-scale patterns and drivers of bird visitation on street fig trees in Delhi, India

Street trees have been used as a means of mitigating the negative effects of urbanization on biodiversity, particularly bird fauna. Despite their widely acknowledged benefits for birds, studies so far have been largely limited to relatively coarse scales, with an understanding of the role of local environments and individual tree characters lacking. We studied the patterns of bird visitation at individual street Ficus (fig) trees, providers of keystone resources in tropical landscapes, in Delhi, India, and their drivers at different scales (tree characteristics, local and landscape variables). Three common fig species were surveyed for bird visitors across 3 sites with varying urban patterns. Fig trees were found to be a relatively common street tree choice, and the 106 trees surveyed were visited by 29 bird species, including 7 obligate frugivores. We found that reducing green cover in surrounding landscape and increasing noise did not deter birds from visiting these trees. Instead, variables at finer scales like tree canopy diameter, tree species and local resource density had sizable and significant effects on both species richness and abundance of bird visitors. Our results highlight how bird assemblages, guilds and individual species respond differently to a range of ecological variables, and an understanding of these responses at different scales is useful for maximising the value of street trees for urban birds. Thus, coarse-scale studies can provide insights into bird diversity of city landscapes, but micro-scale studies are important in helping make fine scale management decisions, like selection of street trees.

The role of biofilm matrix composition in controlling colony expansion and morphology.

Biofilms are biological viscoelastic gels composed of bacterial cells embedded in a self-secreted polymeric extracellular matrix (ECM). In environmental settings, such as in the rhizosphere and phyllosphere, biofilm colonization occurs at the solid-air interface. The biofilms' ability to colonize and expand over these surfaces depends on the formation of osmotic gradients and ECM viscoelastic properties. In this work, we study the influence of biofilm ECM components on its viscoelasticity and expansion, using the model organism Bacillus subtilis and deletion mutants of its three major ECM components, TasA, EPS and BslA. Using a multi-scale approach, we quantified macro-scale viscoelasticity and expansion dynamics. Furthermore, we used a microsphere assay to visualize the micro-scale expansion patterns. We find that the viscoelastic phase angle is likely the best viscoelastic parameter correlating to biofilm expansion dynamics. Moreover, we quantify the sensitivity of the biofilm to changes in substrate water potential as a function of ECM composition. Finally, we find that the deletion of ECM components significantly increases the coherence of micro-scale colony expansion patterns. These results demonstrate the influence of ECM viscoelasticity and substrate water potential on the expansion of biofilm colonies on wet surfaces at the air-solid interface, commonly found in natural environments.

Simultaneous Writing and Erasing Using Probe Lithography Synchronized Erasing and Deposition (PLiSED).

Simultaneous writing and erasing of two and three molecules in one single step at the microscale using Polymeric Lithography Editor (PLE) probes is demonstrated. Simultaneous writing and erasing of three molecules was accomplished by rastering a nanoporous probe that was loaded with rhodamine B and fluorescein over a quinine-coated glass substrate. The solvated quinine molecules were erased and transported into the probe matrix, whereas both rhodamine and fluorescein molecules were simultaneously deposited and aligned with the path of the erased quinine on the substrate. The simultaneous writing and erasing of molecules is referred to as PLiSED. The writing and erasing speed can be easily tuned by adjusting the probe speed to as large as 10,000 μm2/s. The microscale patterns on the orders of square millimeter area were fabricated by erasing fluorescein with an efficiency (ηe) > 95% while simultaneously depositing rhodamine molecules at the erased spots. The roles of the probe porosity, transport medium, and kinetics of solvation for editing were also investigated─the presence of a transport medium at the probe-substrate interface is required for the transport of the molecules into and out of the probe. The physical and mechanical properties of the polymeric probes influenced molecular editing. Young's modulus values of the hydrated hydrogels composed of varying monomer/cross-linker ratios were estimated using atomic force microscopy. Probes with the highest observed erasing capacity were used for further experiments to investigate the effects of relative humidity and erasing time on editing. Careful control over experimental conditions provided high-quality editing of microscale patterns at high editing speed. Combining erasing and deposition of multiple molecules in one single step offers a unique opportunity to significantly improve the efficiency and the accuracy of lithographic editing at the microscale. PLiSED enables rapid on-site lithographic rectification and has considerable application values in high-quality lithography and solid surface modification.

Bridging hollow carbon nanostructures to hierarchically pomegranate-like microspheres for efficient oil adsorption and catalysis applications

Hierarchical carbon superstructures that built from primary nanoscale objects and featured with a micro- or macroscopic architecture are highly desired, as credited by the synergistically integrated specialties. Here, we present a simple “microconfined-assembly-locking” approach to achieve pomegranate-like mesoporous carbon microspheres (PMCMs), in which the Pickering droplet-confined colloidal particle assembly and surfactant-directed interfacial locking are coupled. The formed PMCMs possess a unique micro-nano-hierarchical structure that consisting numerous mesoporous hollow carbon nanospheres within a permeable crust. Benefitting from this hierarchical arrangement, such a peculiar architecture not only preserves high surface area, large pore volume and good accessibility of the nano-building blocks, but also upgrades in mechanical strength and easy handling ability. In addition, this strategy allows the interior microstructures to be manipulated through combinatorial varying the assembled colloidal particles and interfacial chemical locking processes. Notably, the PMCMs show superior sorption capacity and cyclability for organics or oils from water in a fixed-bed system, which could also be applied to enhance the catalytic performance in hydrogenation of aromatic compounds after loading with Ru nanoparticles. This synthetic method provides a powerful bridge between nanoscale objects and microscale patterning, and paves a way to access other novel superstructures for expanding their potential applications.

Ligand-Free Direct Optical Lithography of Bare Colloidal Nanocrystals via Photo-Oxidation of Surface Ions with Porosity Control.

Microscale patterning of colloidal nanocrystal (NC) films is important for their integration in devices. Here, we introduce the direct optical patterning of all-inorganic NCs without the use of additional photosensitive ligands or additives. We determined that photoexposure of ligand-stripped, "bare" NCs in air significantly reduces their solubility in polar solvents due to photo-oxidation of surface ions. Doses as low as 20 mJ/cm2 could be used; the only obvious criterion for material selection is that the NCs need to have significant absorption at the irradiation wavelength. However, transparent NCs can still be patterned by mixing them with suitably absorbing NCs. This approach enabled the patterning of bare ZnSe, CdSe, ZnS, InP, CeO2, CdSe/CdS, and CdSe/ZnS NCs as well as mixtures of ZrO2 or HfO2 NCs with ZnSe NCs. Optical, X-ray photoelectron, and infrared spectroscopies show that solubility loss results from desorption of bound solvent due to photo-oxidation of surface ions. We also demonstrate two approaches, compatible with our patterning method, for modulating the porosity and refractive index of NC films. Block copolymer templating decreases the film density, and thus the refractive index, by introducing mesoporosity. Alternatively, hot isostatic pressing increases the packing density and refractive index of NC layers. For example, the packing fraction of a ZnS NC film can be increased from 0.51 to 0.87 upon hot isostatic pressing at 450 °C and 15 000 psi. Our findings demonstrate that direct lithography by photo-oxidation of bare NC surfaces is an accessible patterning method for facilitating the exploration of more complex NC device architectures while eliminating the influence of bulky or insulating surfactants.

Nanoscale physical unclonable function labels based on block co-polymer self-assembly

Hardware-based cryptography that exploits physical unclonable functions is required for the secure identification and authentication of devices in the Internet of Things. However, physical unclonable functions are typically based on anticounterfeit identifiers created from randomized microscale patterns or non-predictable fluctuations of electrical response in semiconductor devices, and the validation of an encrypted signature relies on a single-purpose method such as microscopy or electrical measurement. Here we report nanoscale physical unclonable function labels that exploit non-deterministic molecular self-assembly. The labels are created from the multilayer superpositions of metallic nanopatterns replicated from self-assembled block co-polymer nanotemplates. Due to the nanoscale dimensions and diverse material options of the system, physical unclonable functions are intrinsically difficult to replicate, robust for authentication and resistant to external disturbance. Multiple, independently operating keys—which use electrical resistance, optical dichroism or Raman signals—can be generated from a single physical unclonable function, offering millisecond-level validation speeds. We also show that our physical unclonable function labels can be used on a range of different surfaces including dollar bills, human hair and microscopic bacteria.

Simulation of Cone-Jet and Micro-Drip Regimes and Printing of Micro-Scale Patterns on PET Substrate.

The fabrication of various micro-patterns on polymer insulating substrates is a current requirement in micro-electromechanical system (MEMS) and packaging sectors. In this paper, we use electrohydrodynamic jet (E-Jet) printing to create multifaceted and stable micro-patterns on a polyethylene terephthalate (PET) substrate. Initially, simulation was performed to investigate optimized printing settings in phase field physics for the usage of two distinct functional inks. A series of simulation experiments was conducted, and it was determined that the following parameters are optimised: applied pressure of 40 kPa, high pulse voltage of 1.95 kV, low dc voltage of 1.60 kV, duty cycle of 80%, pulse frequency of 60 Hz, printing height of 0.25 mm, and printing speed of 1 mm/s. Then, experiments showed that adjusting a pressure value of 40 kPa and regulating the SEMICOSIL988/1 K ink to print micro-drops on a polymer substrate with a thickness of 1 mm prevents coffee staining. The smallest measured droplet size was 200 μm. Furthermore, underfill (UF 3808) ink was driven with applied pressure to 50 kPa while other parameters were left constant, and the minimum size of linear patterns was printed to 105 μm on 0.5-mm-thick PET substrate. During the micro-drip and cone-jet regimes, the consistency and diameter of printed micro-structures were accurately regulated at a pulse frequency of 60 Hz and a duty cycle of 80%.

Phase diagrams on composition-spread FeyTe1−xSex films

FeyTe1−xSex, an archetypical iron-based high-temperature superconductor with a simple structure but rich physical properties, has attracted lots of attention because the two end compositions, Se content x = 0 and 1, exhibit antiferromagnetism and nematicity, respectively, making it an ideal candidate for studying their interactions with superconductivity. However, what is clearly lacking to date is a complete phase diagram of FeyTe1−xSex as functions of its chemical compositions since phase separation usually occurs from x ∼ 0.6 to 0.9 in bulk crystals. Moreover, fine control of its composition is experimentally challenging because both Te and Se are volatile elements. Here we establish a complete phase diagram of FeyTe1−xSex, achieved by high-throughput film synthesis and characterization techniques. An advanced combinatorial synthesis process enables us to fabricate an epitaxial composition-spread FeyTe1−xSex film encompassing the entire Se content x from 0 to 1 on a single piece of CaF2 substrate. The micro-region composition analysis and X-ray diffraction show a successful continuous tuning of chemical compositions and lattice parameters, respectively. The micro-scale pattern technique allows the mapping of electrical transport properties as a function of relative Se content with an unprecedented resolution of 0.0074. Combining with the spin patterns in literature, we build a detailed phase diagram that can unify the electronic and magnetic properties of FeyTe1−xSex. Our composition-spread FeyTe1−xSex films, overcoming the challenges of phase separation and precise control of chemical compositions, provide an ideal platform for studying the relationship between superconductivity and magnetism.

Aerosol Jet Printing as a Versatile Sample Preparation Method for Operando Electrochemical TEM Microdevices

AbstractOperando electrochemical transmission electron microscopy (ec‐TEM) is a promising tool for advanced characterization of energy systems close to their operating conditions. However, reliable sample preparation for the technique is particularly challenging due to spatial constraints. Here, a novel approach of manufacturing such samples is introduced and demonstrated for industrially relevant battery powders: NMC811 and LTO (LiNi0.8Mn0.1Co0.1O2 and Li4Ti5O12). Aerosol‐jet printing is used to deposit microscale patterns of battery active material particles on the electrodes of commercial ec‐TEM chips. This method provides high spatial resolution (line width &lt; 30 µm) and accuracy, ease of ink preparation, flexibility of materials, and ability to manufacture complex structures (layered or mixed materials). Size selectivity of aerosol jet printing and its positive implications for ec‐TEM sample preparation are also discussed. This procedure is a promising solution to the difficult problem of micro‐battery fabrication for ec‐TEM and for other applications where high spatial resolution deposition from powders is required.

Competition for shared downstream signaling molecules establishes indirect negative feedback between EGFR and EphA2

Cells sense a variety of extracellular growth factors and signaling molecules through numerous distinct receptor tyrosine kinases (RTKs) on the cell surface. In many cases, the same intracellular signaling molecules interact with more than one type of RTK. How signals from different RTKs retain the identity of the triggering receptor and how (or if) different receptors may synergize or compete remain largely unknown. Here we utilize an experimental strategy, combining microscale patterning and single-molecule imaging, to measure the competition between ephrin-A1:EphA2 and epidermal growth factor (EGF):EGF receptor (EGFR) ligand-receptor complexes for the shared downstream signaling molecules, Grb2 and SOS. The results reveal a distinct hierarchy, in which newly formed EGF:EGFR complexes outcompete ephrin-A1:EphA2 for Grb2 and SOS, revealing a type of negative crosstalk interaction fundamentally controlled by chemical mass action and protein copy number limitations.

Enhanced Light Extraction from Organic Light-Emitting Diodes with Micro-Nano Hybrid Structure.

In this study, an external light extraction layer with a micro-nano hybrid structure was applied to improve the external light extraction efficiency of organic light-emitting diodes (OLEDs). A reactive ion-etching (RIE) process, using O2 and CHF3 plasma, was performed on the surface of the micro-scale pattern to form micro-nano hybrid structures. According to the results of this study, the nanostructures formed by the treatment of O2 and CHF3 were different, and the efficiency according to the structures was analyzed experimentally and theoretically. As a result, the OLED, to which the micro-nano hybrid structure, manufactured through a simple process, is applied, improved the external light extraction efficiency by up to 38%, and an extended viewing angle profile was obtained. Additionally, an effective method for enhancing the out-coupling efficiency of OLEDs was presented by optimizing the micro-nano hybrid structure according to process conditions.