Emulsion Designer Using Microfluidic Three-Dimensional Droplet Printing in Droplet

Fringe Texture Driven Droplet Measurement End-to-End Network Based on Physics Aberrations Restoration of Coherence Scanning Interferometry

Accurate and efficient measurement of deposited droplets' volume is vital to achieve zero-defect manufacturing in inkjet printed organic light-emitting diode (OLED), but it remains a challenge due to droplets' featurelessness. In our work, coherence scanning interferometry (CSI) is utilized to measure the volume. However, the CSI redundant sampling and image degradation led by the sample's transparency decrease the efficiency and accuracy. Based on the prior degradation and strong representation for context, a novel method, volume measurement via fringe distribution module (VMFD), is proposed to directly measure the volume by single interferogram without redundant sampling. Firstly, the 3D point spread function (PSF) for CSI imaging is modeling to relate the degradation and image. Secondly, the Zernike to PSF (ZTP) module is proposed to efficiently compute the aberrations to PSF. Then, a physics aberration restoration network (PARN) is designed to remove the degradation via the channel Transformer and U-net architecture. The long term context is learned by PARN and beneficial to restoration. The restored fringes are used to measure the droplet's volume by constrained regression network (CRN) module. Finally, the performances on public datasets and the volume measurement experiments show the promising deblurring, measurement precision and efficiency.

Jammed Pickering Emulsion Gels

Emulsion gels with specific rheological properties have widespread applications in foods, cosmetics, and biomedicines. However, the constructions of water-in-oil emulsion gels are still challenging, due to the limited interactions available in the continuous oil phase. Here, a versatile strategy is developed to prepare a new type of emulsion gels, called Jammed Pickering emulsion gels (JPEGs). In the JPEG system, SiO2 NPs in the oil phase serve as colloidal surfactants to stabilize water-in-oil Pickering emulsions, while positively-charged NH2-PEG-NH2 molecules in the water phase cross-link negatively-charged SiO2 NPs at the water/oil interface, making NP-stabilized water droplets hard to deform and thus jamming the emulsion system to form emulsion gels. The strategy to prepare JPEGs is versatile and applicable to diverse oil phases. The designed JPEGs possess many advantages, including good biocompatibility for widespread applications, shear-thinning rheological properties for easy processing, good stability Over a wide temperature range and Against centrifugation, good adhesion to wet tissues for tissue engineering, and well-controlled sustained release Under intestinal conditions. The developed JPEGs are demonstrated to be a promising delivery platform and the strategy to achieve JPEGs will trigger more innovations of material design.

All-Aqueous Embedded 3D Printing for Freeform Fabrication of Biomimetic 3D Constructs

All-aqueous embedded 3D printing, which involves extruding inks in an aqueous bath, has emerged as a transformative platform for the freeform fabrication of 3D constructs with precise control. The use of a supporting bath not only enables the printing of arbitrarily designed 3D constructs but also broadens ink selection for various soft matters, advancing the wide application of this technology. This review focuses on recent progress in the freeform preparation of 3D constructs using all-aqueous embedded 3D printing. It begins by discussing the significance of ultralow interfacial tension in all-liquid embedded printing and highlights the fundamental concepts and properties of all-aqueous system. The review then introduces recent advances in all-aqueous embedded 3D printing and clarifies the key factors affecting printing stability and shape fidelity, aiming to guide expansion and assessment of emerging printing systems used for various representative applications. Furthermore, it proposes the potential scope and applications of this technology, including in vitro models, cytomimetic microreactors, and soft ionic electronics. Finally, the review discusses the challenges facing current all-aqueous embedded 3D printing and offers future perspectives on possible improvements and developments.

Microfluidic Printing of Vertically-Oriented Nanosheets/MOFs Hetero-Interface for Intensive Pseudocapacitive Storage

Efficient manufacture of electroactive vertically-oriented nanosheets with enhanced electrolyte mass diffusion and strong interfacial redox dynamics is critical for realizing high energy density of miniature supercapacitor (SC), but still challenging. Herein, microfluidic droplet printing is developed to controllably construct vertically-oriented graphene/ZIF-67 hetero-microsphere (VAGS/ZIF-67), where the ZIF-67 is coordinately grown on vertically-oriented graphene framework via Co─O─C bonds. The VAGS/ZIF-67 shows ordered porous channel, high electroactivity and strong interfacial interaction, providing rapid electrolyte diffusion dynamics and high faradaic capacitance in KOH solution (1674 F g-1 , 1004 C g-1 ), which are verified by computational fluid dynamics (CFD) and density functional theory (DFT). Moreover, the VAGS/ZIF-67 based SC exhibits large energy density (100 Wh kg-1 ), excellent durability (10 000 cycles and high/low temperature), and robust power-supply applications in portable electronics.

Facile and Programmable Capillary-Induced Assembly of Prototissues via Hanging Drop Arrays

An important goal for bottom-up synthetic biology is to construct tissue-like structures from artificial cells. The key is the ability to control the assembly of the individual artificial cells. Unlike most methods resorting to external fields or sophisticated devices, inspired by the hanging drop method used for culturing spheroids of biological cells, we employ a capillary-driven approach to assemble giant unilamellar vesicles (GUVs)-based protocells into colonized prototissue arrays by means of a coverslip with patterned wettability. By spatially confining and controllably merging a mixed population of lipid-coated double-emulsion droplets that hang on a water/oil interface, an array of synthetic tissue-like constructs can be obtained. Each prototissue module in the array comprises multiple tightly packed droplet compartments where interfacial lipid bilayers are self-assembled at the interfaces both between two neighboring droplets and between the droplet and the external aqueous environment. The number, shape, and composition of the interconnected droplet compartments can be precisely controlled. Each prototissue module functions as a processer, in which fast signal transports of molecules via cell-cell and cell-environment communications have been demonstrated by molecular diffusions and cascade enzyme reactions, exhibiting the ability to be used as biochemical sensing and microreactor arrays. Our work provides a simple yet scalable and programmable method to form arrays of prototissues for synthetic biology, tissue engineering, and high-throughput assays.

Preparation and Magnetic Manipulation of Fe3O4/Acrylic Resin Core-Shell Microspheres

Core-shell microspheres refer to duo-layer or multilayer microspheres, which are widely used in drug delivery, microreactors, etc. Accurate manipulation of microspheres is a research hot spot, while traditional manipulation methods including ultrasonic manipulation and laser manipulation still face some limitations. In this study, magnetic core-shell microspheres were adopted to realize the accurate manipulation of microspheres. Combined with microfluidic technology, polystyrene sulfonic acid (PSSA)/Fe3O4 magnetic fluid was utilized as the core material and photosensitive acrylic resin became the shell material. After UV curing, a magnetic core-shell microsphere with an average size of 55 μm could be achieved, and the diameter was uniform and controllable. By adjusting the flow rate of the dispersed phase, the dual-core microspheres with different core particle sizes that ranged from 9.3 to 28.4 μm could be prepared. Experimental results showed that the prepared Fe3O4/acrylic resin core-shell microspheres can be used as functionalized microspheres that have good magnetic response properties and self-assembly ability. In addition, the magnetic manipulation and self-assembly of the prepared core-shell microspheres were presented with different external magnetic fields. The magnetic core-shell microspheres have shown great potential in the fields of biomedical engineering and targeted delivery of drugs.

Flow cytometric printing of double emulsions into open droplet arrays

Delivery of double emulsions in air is crucial for their applications in mass spectrometry, bioanalytics, and material synthesis. However, while methods have been developed to generate double emulsions in air, controlled printing of double emulsion droplets has not been achieved yet. In this paper, we present an approach for in-air printing of double emulsions on demand. Our approach pre-encapsulates reagents in an emulsion that is reinjected into the device, and generates double emulsions in a microfluidic printhead with spatially patterned wettability. Our device allows sorting of ejected double emulsion droplets in real-time, allowing deterministic printing of each droplet to be selected with the desired inner cores. Our method provides a general platform for building printed double emulsion droplet arrays of defined composition at scale.

Basic fibroblast growth factor-loaded methacrylate gelatin hydrogel microspheres for spinal nerve regeneration

Spinal cord injury is a severe central nervous system injury, and developing appropriate drug delivery platforms for spinal nerve regeneration is highly anticipated. Here, we propose a basic fibroblast growth factor (bFGF)-loaded methacrylate gelatin (GelMA) hydrogel microsphere with ideal performances for spinal cord injury repair. Benefitting from the precise droplet manipulation capability of the microfluidic technology, the GelMA microspheres possess uniform and satisfactory size and good stability. More importantly, by taking advantage of the porous structures and facile chemical modification of the GelMA microspheres, bFGF could be easily loaded and gradually released. By co-culturing with neural stem cells, it is validated that the bFGF-loaded GelMA microspheres could effectively promote the proliferation and differentiation of neural stem cells. We also confirm the effective role of the bFGF-loaded GelMA microspheres in nerve repair of spinal cord injury in rats. Our results demonstrate the potential value of the microspheres for applications in repairing central nervous system injuries.

Floating Hydrogel Beads Made by Droplet Impact

Droplet impact is a ubiquitous natural phenomenon that has been widely utilized to inspire and facilitate many industrial applications. Compared to the widely studied water droplet impact onto identical liquid surfaces, the water droplet impact onto an oil layer floating on a water bath (OLW) receives far less attention and its potential application has never been exploited. Herein, the process of water droplet impact onto the OLW is investigated with emphasis on the metastable states and potential applications. It is found that the dramatic deformation of the oil-water interface caused by the water droplet impact leads to two metastable states: oil in water in oil in water (O/W/O/W) and oil in water in oil (O/W/O). Through the subsequent introduction of gelation process, the metastable states can be frozen into floating hydrogel beads with similar shape to the roly-poly toys, which are attempted in gastric retentive drug delivery and algae bloom control. Specifically, the floating hydrogel beads perform well in gastric retentive drug delivery in vitro due to their inherent slow-release properties and floating capability. In addition, the floating hydrogel beads loading photocatalysts can capture more sunshine, and exhibit high photocatalytic efficiency, which is thus responsible for efficient algae bloom control.

Structured Ultra-Flyweight Aerogels by Interfacial Complexation: Self-Assembly Enabling Multiscale Designs

The rapid co-assembly of graphene oxide (GO) nanosheets and a surfactant at the oil/water (O/W) interface is harnessed to develop a new class of soft materials comprising continuous, multilayer, interpenetrated, and tubular structures. The process uses a microfluidic approach that enables interfacial complexation of two-phase systems, herein, termed as "liquid streaming" (LS). LS is demonstrated as a general method to design multifunctional soft materials of specific hierarchical order and morphology, conveniently controlled by the nature of the oil phase and extrusion's injection pressure, print-head speed, and nozzle diameter. The as-obtained LS systems can be readily converted into ultra-flyweight aerogels displaying worm-like morphologies with multiscale porosities (micro- and macro-scaled). The presence of reduced GO nanosheets in such large surface area systems renders materials with outstanding mechanical compressibility and tailorable electrical activity. This platform for engineering soft materials and solid constructs opens up new horizons toward advanced functionality and tunability, as demonstrated here for ultralight printed conductive circuits and electromagnetic interference shields.

PDMS Microfabrication and Design for Microfluidics and Sustainable Energy Application: Review

The polydimethylsiloxane (PDMS) is popular for wide application in various fields of microfluidics, microneedles, biology, medicine, chemistry, optics, electronics, architecture, and emerging sustainable energy due to the intrinsic non-toxic, transparent, flexible, stretchable, biocompatible, hydrophobic, insulating, and negative triboelectric properties that meet different requirements. For example, the flexibility, biocompatibility, non-toxicity, good stability, and high transparency make PDMS a good candidate for the material selection of microfluidics, microneedles, biomedical, and chemistry microchips as well as for optical examination and wearable electronics. However, the hydrophobic surface and post-surface-treatment hydrophobic recovery impede the development of self-driven capillary microchips. How to develop a long-term hydrophilicity treatment for PDMS is crucial for capillary-driven microfluidics-based application. The dual-tone PDMS-to-PDMS casting for concave-and-convex microstructure without stiction is important for simplifying the process integration. The emerging triboelectric nanogenerator (TENG) uses the transparent flexible PDMS as the high negative triboelectric material to make friction with metals or other positive-triboelectric material for harvesting sustainably mechanical energy. The morphology of PDMS is related to TENG performance. This review will address the above issues in terms of PDMS microfabrication and design for the efficient micromixer, microreactor, capillary pump, microneedles, and TENG for more practical applications in the future.

Interfacial Engineering of Attractive Pickering Emulsion Gel-Templated Porous Materials for Enhanced Solar Vapor Generation

Solar vapor generation is emerging as one of the most important sustainable techniques for harvesting clean water using abundant and green solar energy. The rational design of solar evaporators to realize high solar evaporation performances has become a great challenge. Here, a porous solar evaporator with integrative optimization of photothermal convention, water transport and thermal management is developed using attractive Pickering emulsions gels (APEG) as templated and followed by interfacial engineering on a molecular scale. The APEG-templated porous evaporators (APEG-TPEs) are intrinsically thermal insulation materials with a thermal conductivity = 0.039 W·m−1·K−1. After hydrolysis, t-butyl groups on the inner-surface are transformed to carboxylic acid groups, making the inner-surface hydrophilic and facilitating water transport through the inter-connected pores. The introduction of polypyrrole layer endows the porous materials with a high light absorption of ~97%, which could effectively convert solar irradiation to heat. Due to the versatility of the APEG systems, the composition, compressive modulus, porosity of APEG-TPEs could be well controlled and a high solar evaporation efficiency of 69% with an evaporation rate of 1.1 kg·m−2·h−1 is achieved under simulated solar irradiation. The interface-engineered APEG-TPEs are promising in clean water harvesting and could inspire the future development of solar evaporators.