Direct 3D Printed Biomimetic Scaffolds Based on Hydrogel Microparticles for Cell Spheroid Growth

Biocompatible hydrogel inks with shear‐thinning, appropriate yield strength, and fast self‐healing are desired for 3D bioprinting. However, the lack of ideal 3D bioprinting inks with outstanding printability and high structural fidelity, as well as cell‐compatibility, has hindered the progress of extrusion‐based 3D bioprinting for tissue engineering. In this study, novel self‐healable pre‐cross‐linked hydrogel microparticles (pcHμPs) of chitosan methacrylate (CHMA) and polyvinyl alcohol (PVA) hybrid hydrogels are developed and used as bioinks for extrusion‐based 3D printing of scaffolds with high fidelity and biocompatibility. The pcHμPs display excellent shear thinning when injected through a syringe and subsequently self‐heal into gels as shear forces are removed. Numerical simulations indicate that the pcHμPs experience a plug flow in the nozzle with minimal disturbance, which favors a steady and continuous printing. Moreover, the pcHμPs show a self‐supportive yield strength (540 Pa), which is critical for the fidelity of printed constructs. A series of biomimetic constructs with very high aspect ratio and delicate fine structures are directly printed by using the pcHμP ink. The 3D printed scaffolds support the growth of bone‐marrow‐derived mesenchymal stem cells and formation of cell spheroids, which are most important for tissue engineering.     

3D Printed Stem‐Cell Derived Neural Progenitors Generate Spinal Cord Scaffolds

A bioengineered spinal cord is fabricated via extrusion‐based multimaterial 3D bioprinting, in which clusters of induced pluripotent stem cell (iPSC)‐derived spinal neuronal progenitor cells (sNPCs) and oligodendrocyte progenitor cells (OPCs) are placed in precise positions within 3D printed biocompatible scaffolds during assembly. The location of a cluster of cells, of a single type or multiple types, is controlled using a point‐dispensing printing method with a 200 µm center‐to‐center spacing within 150 µm wide channels. The bioprinted sNPCs differentiate and extend axons throughout microscale scaffold channels, and the activity of these neuronal networks is confirmed by physiological spontaneous calcium flux studies. Successful bioprinting of OPCs in combination with sNPCs demonstrates a multicellular neural tissue engineering approach, where the ability to direct the patterning and combination of transplanted neuronal and glial cells can be beneficial in rebuilding functional axonal connections across areas of central nervous system (CNS) tissue damage. This platform can be used to prepare novel biomimetic, hydrogel‐based scaffolds modeling complex CNS tissue architecture in vitro and harnessed to develop new clinical approaches to treat neurological diseases, including spinal cord injury.     

Advances in 4D Printing: Materials and Applications

4D printing has attracted tremendous interest since its first conceptualization in 2013. 4D printing derived from the fast growth and interdisciplinary research of smart materials, 3D printer, and design. Compared with the static objects created by 3D printing, 4D printing allows a 3D printed structure to change its configuration or function with time in response to external stimuli such as temperature, light, water, etc., which makes 3D printing alive. Herein, the material systems used in 4D printing are reviewed, with emphasis on mechanisms and potential applications. After a brief overview of the definition, history, and basic elements of 4D printing, the state‐of‐the‐art advances in 4D printing for shape‐shifting materials are reviewed in detail. Both single material and multiple materials using different mechanisms for shape changing are summarized. In addition, 4D printing of multifunctional materials, such as 4D bioprinting, is briefly introduced. Finally, the trend of 4D printing and the perspectives for this exciting new field are highlighted.     

Bioinspired Development of an In Vitro Engineered Fracture Callus for the Treatment of Critical Long Bone Defects

Cell-based regenerative constructs provide hope for the restoration of tissue function in compromised biological conditions such as complex bone defects. A strategy mimicking the cascade of events of postnatal fracture healing suggests an implant design where progenitor cells provide the driving force for the construct's tissue forming capacity, while framing biomaterials provide cells with 3D cues to direct cellular processes. Large bone defects mainly heal through the formation of an intermediate endochondral fracture callus. The authors aimed to develop an in vitro engineered fracture callus manufactured by bioprinting to provide a spatially organized tissue construct based on: i) in vitro 3D primed human periosteum derived cells and ii) biocompatible thiol-ene alginate hydrogels, mimicking the cells and extracellular matrix present in the different zones of the callus. Cell viability and maintained osteochondrogenic differentiation upon bioprinting is confirmed in vitro. In vivo assessment displays that the developed biomaterials provided essential 3D cues that further guided the cells in their tissue forming process in the absence of additional stimulatory molecules. The reported findings confirm the appeal of a biomimetic approach to steer tissue development of in vitro engineered constructs and illustrate the suitability of bioprinting methodologies for the fabrication of living regenerative implants.     

Soft Electronics Manufacturing Using Microcontact Printing

This work describes a microcontact printing (µCP) process for reproducible manufacturing of liquid gallium alloy–based soft and stretchable electronics. One of the leading approaches to create soft and stretchable electronics involves embedding liquid metals (LM) into an elastomer matrix. Although the advantages of liquid metal–based electronics have been well established, their mainstream adoption and commercialization necessitates development of precise and scalable manufacturing methods. To address this need, a scalable µCP process is presented that uses surface‐functionalized, reusable rigid, or deformable stamps to transfer eutectic gallium–indium (EGaIn) patterns onto elastomer substrates. A novel approach is developed to create the surface‐functionalized stamps, enabling selective transfer of LM to desired locations on a substrate without residues or electrical shorts. To address the critical needs of precise and reproducible positioning, alignment, and stamping force application, a high‐precision automated µCP system is designed. After describing the approach, the precision of stamps is evaluated and EGaIn features (as small as 15 µm line width), as well as electrical functionality of printed circuits with and without deformation, are fabricated. The presented process addresses many of the limitations associated with the alternative fabrication processes, and thus provides an effective approach for scalable fabrication of LM‐based soft and stretchable microelectronics.     

A Synthetic Dynamic Polyvinyl Alcohol Photoresin for Fast Volumetric Bioprinting of Functional Ultrasoft Hydrogel Constructs

Tomographic volumetric bioprinting (VBP) enables fast photofabrication of cell-laden hydrogel constructs in one step, addressing the limitations of conventional layer-by-layer additive manufacturing. However, existing biomaterials that fulfill the physicochemical requirements of VBP are limited to gelatin-based photoresins of high polymer concentrations. The printed microenvironments are predominantly static and stiff, lacking sufficient capacity to support 3D cell growth. Here a dynamic resin based on thiol–ene photo-clickable polyvinyl alcohol (PVA) and thermo-sensitive sacrificial gelatin for fast VBP of functional ultrasoft cell-laden hydrogel constructs within 7–15 s is reported. Using gelatin allows VBP of permissive hydrogels with low PVA contents of 1.5%, providing a stress-relaxing environment for fast cell spreading, 3D osteogenic differentiation of embedded human mesenchymal stem cells and matrix mineralization. Additionally, site-specific immobilization of molecules-of-interest inside a PVA hydrogel is achieved by 3D tomographic thiol–ene photopatterning. This technique may enable spatiotemporal control of cell-material interactions and guides in vitro tissue formation using programmed cell-friendly light. Altogether, this study introduces a synthetic dynamic photoresin enabling fast VBP of functional ultrasoft hydrogel constructs with well-defined physicochemical properties and high efficiency.     

Targeted Single‐Cell Therapeutics with Magnetic Tubular Micromotor by One‐Step Exposure of Structured Femtosecond Optical Vortices

Selective manipulation of specific single cells for therapeutics is important and highly desirable in biomedical research. As a simple and maneuverable tool, tubular micromotors have displayed appealing applications in encapsulation and transportation of cells. However, so far there are no reports on the simultaneous transportation of target single cells and the drugs with microtubes in a custom arrayed environment for targeted therapeutics. Moreover, fabrication of microtubes with 3D features in a reproducible and single‐step fashion, while, endowing them with the ability of remote control, remains challenging. In this study, a novel method for one‐step fabrication of magnetic 3D tubular micromotors by single exposure of structured optical vortices in a magnetic photoresist is presented. The size and geometry of fabricated microtubes are flexibly controlled in three dimensions. Precise propelling of the tubular micromotors and precise capture, targeted delivery, and release of SiO₂ microparticles are realized. Finally, as a proof‐of‐concept demonstration, in situ observation of the development of doxorubicin in Hela cells for therapeutic study is performed by targeted delivery of single cells and drug particles. The technology is simple and stable, which has promising applications in targeted cell therapy, drug screening, single cell studies, and other biomedical areas.     

Programming Delayed Dissolution Into Sacrificial Bioinks For Dynamic Temporal Control of Architecture within 3D-Bioprinted Constructs

Sacrificial printing allows introduction of architectural cues within engineered tissue constructs. This strategy adopts the use of a 3D-printed sacrificial ink that is embedded within a bulk hydrogel which is subsequently dissolved to leave open-channels. However, current conventional sacrificial inks do not recapitulate the dynamic nature of tissue development, such as the temporal presentation of architectural cues matching cellular requirements during different stages of maturation. To address this limitation, a new class of sacrificial inks is developed that exhibits tailorable and programmable delayed dissolution profiles (1–17 days), by exploiting the unique ability of the ruthenium complex and sodium persulfate initiating system to crosslink native tyrosine groups present in non-chemically modified gelatin. These novel sacrificial inks are also shown to be compatible with a range of biofabrication technologies, including extrusion-based printing, digital-light processing, and volumetric bioprinting. Further embedding these sacrificial templates within cell-laden bulk hydrogels displays precise control over the spatial and temporal introduction of architectural features into cell-laden hydrogel constructs. This approach demonstrates the unique capacity of delaying dissolution of sacrificial inks to modulate cell behavior, improving the deposition of mineralized matrix and capillary-like network formation in osteogenic and vasculogenic culture, respectively.     

车载式北斗光学三维成像系统技术研究

本文论述了车载式光学成像系统的定位原理,在此基础之上,设计实现车载式北斗光学三维成像系统,该成像系统通过北斗高精度接收机实现成像系统的中心点位置解算,并辅助惯导设备实现成像系统姿态信息解算。通过对比试验,分析说明北斗高精度定位在光学三维成像中发挥的重要价值及成像系统优化方向。北斗定位传感器与光学传感器的有机结合,对提升光学图像信息的有效获取、特定目标的精准感知意义非凡。     

基于PCA-TrICP的多源点云无缝三维重建

针对三维重建时使用单一数据源的局限性问题,融合异源的倾斜影像和三维激光点云进行三维实景重建.在前期工作中,利用倾斜摄影技术对校园图书馆建立初始模型,生成影像点云,并使用三维激光扫描仪获取其立面数据,完成去噪及拼接等预处理工作.针对预处理过后的影像点云和激光点云数据的配准,首先使用主成分分析方法对数据降低维度,对齐跨源点...     

Intra-Operative Bioprinting of Hard,Soft, and Hard/Soft Composite Tissues for Craniomaxillofacial Reconstruction

Reconstruction of complex craniomaxillofacial (CMF) defects is challenging due to the highly organized layering of multiple tissue types. Such compartmentalization necessitates the precise and effective use of cells and other biologics to recapitulate the native tissue anatomy. In this study, intra-operative bioprinting (IOB) of different CMF tissues, including bone, skin, and composite (hard/soft) tissues, is demonstrated directly on rats in a surgical setting. A novel extrudable osteogenic hard tissue ink is introduced, which induced substantial bone regeneration, with ≈80% bone coverage area of calvarial defects in 6 weeks. Using droplet-based bioprinting, the soft tissue ink accelerated the reconstruction of full-thickness skin defects and facilitated up to 60% wound closure in 6 days. Most importantly, the use of a hybrid IOB approach is unveiled to reconstitute hard/soft composite tissues in a stratified arrangement with controlled spatial bioink deposition conforming the shape of a new composite defect model, which resulted in ≈80% skin wound closure in 10 days and 50% bone coverage area at Week 6. The presented approach will be absolutely unique in the clinical realm of CMF defects and will have a significant impact on translating bioprinting technologies into the clinic in the future.     

Controllable Patterning of Different Cells Via Optical Assembly of 1D Periodic Cell Structures

Flexible patterning of different cells into designated locations with direct cell–cell contact at single‐cell patterning precision and control is of great importance, however challenging, for cell patterning. Here, an optical assembly method for patterning of different types of cells via direct cell–cell contact at single‐cell patterning precision and control is demonstrated. Using Escherichia coli and Chlorella cells as examples, different cells are flexibly patterned into 1D periodic cell structures (PCSs) with controllable configurations and lengths, by periodically connecting one type of cells with another by optical force. The patterned PCSs can be flexibly moved and show good light propagation ability. The propagating light signals can be detected in real‐time, providing new opportunities for the detection of transduction signals among patterned cells. This patterning method is also applicable for cells of other kinds, including mammalian/human cells.     

Void‐Free 3D Bioprinting for In Situ Endothelialization and Microfluidic Perfusion

Two major challenges of 3D bioprinting are the retention of structural fidelity and efficient endothelialization for tissue vascularization. Both of these issues are addressed by introducing a versatile 3D bioprinting strategy, in which a templating bioink is deposited layer‐by‐layer alongside a matrix bioink to establish void‐free multimaterial structures. After crosslinking the matrix phase, the templating phase is sacrificed to create a well‐defined 3D network of interconnected tubular channels. This void‐free 3D printing (VF‐3DP) approach circumvents the traditional concerns of structural collapse, deformation, and oxygen inhibition, moreover, it can be readily used to print materials that are widely considered “unprintable.” By preloading endothelial cells into the templating bioink, the inner surface of the channels can be efficiently cellularized with a confluent endothelial layer. This in situ endothelialization method can be used to produce endothelium with a far greater cell seeding uniformity than can be achieved using the conventional postseeding approach. This VF‐3DP approach can also be extended beyond tissue fabrication and toward customized hydrogel‐based microfluidics and self‐supported perfusable hydrogel constructs.     

A Stimuli‐Responsive Nanocomposite for 3D Anisotropic Cell‐Guidance and Magnetic Soft Robotics

Stimuli‐responsive materials have the potential to enable the generation of new bioinspired devices with unique physicochemical properties and cell‐instructive ability. Enhancing biocompatibility while simplifying the production methodologies, as well as enabling the creation of complex constructs, i.e., via 3D (bio)printing technologies, remains key challenge in the field. Here, a novel method is presented to biofabricate cellularized anisotropic hybrid hydrogel through a mild and biocompatible process driven by multiple external stimuli: magnetic field, temperature, and light. A low‐intensity magnetic field is used to align mosaic iron oxide nanoparticles (IOPs) into filaments with tunable size within a gelatin methacryloyl matrix. Cells seeded on top or embedded within the hydrogel align to the same axes of the IOPs filaments. Furthermore, in 3D, C2C12 skeletal myoblasts differentiate toward myotubes even in the absence of differentiation media. 3D printing of the nanocomposite hydrogel is achieved and creation of complex heterogeneous structures that respond to magnetic field is demonstrated. By combining the advanced, stimuli‐responsive hydrogel with the architectural control provided by bioprinting technologies, 3D constructs can also be created that, although inspired by nature, express functionalities beyond those of native tissue, which have important application in soft robotics, bioactuators, and bionic devices.     

Patterning of organic photovoltaic modules by ultrafast laser

In this paper, we demonstrate that laser patterning of organic solar cells by ultrafast laser systems (pulse length <350 fs) is an attractive process to produce photovoltaic modules with outstanding high geometric fill factors. Moreover, in terms of precision, registration, and debris generation and in terms of keeping the damage to the underneath layers at a minimum, ultrafast laser patterning with a pulse length of few hundreds of femtoseconds turns out to yield superior results. Ablation of all three different solar cell layers (electrodes (P1 and P3) and interfaces and semiconductor (P2)) is achieved with a single wavelength simply by a precise adjustment of the laser fluence and the patterning overlap. Camera positioning allows a precise registration between the various processing steps and a reduction of the width of the overall interconnection regime to the hundreds of micrometers dimension, resulting in high geometrical fill factors of over 90% for monolithically interconnected organic solar cell modules. Copyright © 2013 John Wiley & Sons, Ltd.     

Tunable Nanoparticle and Cell Assembly Using Combined Self‐Powered Microfluidics and Microcontact Printing

The combination of cell microenvironment control and real‐time monitoring of cell signaling events can provide key biological information. Through precise multipatterning of gold nanoparticles (GNPs) around cells, sensing and actuating elements can be introduced in the cells' microenviroment, providing a powerful substrate for cell studies. In this work, a combination of techniques are implemented to engineer complex substrates for cell studies. Alternating GNPs and bioactive areas are created with micrometer separation by means of a combination of vacumm soft‐lithography of GNPs and protein microcontract printing. Instead of conventional microfluidics that need syringe pumps to flow liquid in the microchannels, degas driven flow is used to fill dead‐end channels with GNP solutions, rendering the fabrication process straightforward and accessible. This new combined technique is called Printing and Vacuum lithography (PnV lithography). By using different GNPs with various organic coating ligands, different macroscale patterns are obtained, such as wires, supercrystals, and uniformly spread nanoparticle layers that can find different applications depending on the need of the user. The application of the system is tested to pattern a range of mammalian cell lines and obtain readouts on cell viability, cell morphology, and the presence of cell adhesive proteins.     

WCDMA位置服务平台建设策略

WCDMA规范中主要有3种定位技术：基于小区识别（CELLID）的定位技术、可观测不同到达时间（OTDOA）定位技术和网络辅助的全球定位系统（GPS）定位技术。基于CELLID的定位方法可以在定位精度要求较低时使用；OTDOA方法可以在定位精度要求较高并且终端和网络无GPS接收装置时使用；而基于应用层的全球定位系统（A—GPS）定位方法则适宜定位精度要求高且终端和网络有GPS接收装置时使用。在WCDMA发展初期，位置服务平台的建设应考虑2G／3G混合组网的实际情况，平台应能同时支持2G和3G用户，技术上应能够支持A—GPS定位技术。     

Hydrodynamically Guided Hierarchical Self‐Assembly of Peptide–Protein Bioinks

Effective integration of molecular self‐assembly and additive manufacturing would provide a technological leap in bioprinting. This article reports on a biofabrication system based on the hydrodynamically guided co‐assembly of peptide amphiphiles (PAs) with naturally occurring biomolecules and proteins to generate hierarchical constructs with tuneable molecular composition and structural control. The system takes advantage of droplet‐on‐demand inkjet printing to exploit interfacial fluid forces and guide molecular self‐assembly into aligned or disordered nanofibers, hydrogel structures of different geometries and sizes, surface topographies, and higher‐ordered constructs bound by molecular diffusion. PAs are designed to co‐assemble during printing in cell diluent conditions with a range of extracellular matrix (ECM) proteins and biomolecules including fibronectin, collagen, keratin, elastin‐like proteins, and hyaluronic acid. Using combinations of these molecules, NIH‐3T3 and adipose derived stem cells are bioprinted within complex structures while exhibiting high cell viability (>88%). By integrating self‐assembly with 3D‐bioprinting, the study introduces a novel biofabrication platform capable of encapsulating and spatially distributing multiple cell types within tuneable pericellular environments. In this way, the work demonstrates the potential of the approach to generate complex bioactive scaffolds for applications such as tissue engineering, in vitro models, and drug screening.     

3D Bioprinting using UNIversal Orthogonal Network (UNION) Bioinks

Three-dimensional (3D) bioprinting is a promising technology to produce tissue-like structures, but a lack of diversity in bioinks is a major limitation. Ideally each cell type would be printed in its own customizable bioink. To fulfill this need for a universally applicable bioink strategy, a versatile bioorthogonal bioink crosslinking mechanism that is cell compatible and works with a range of polymers is developed. This family of materials is termed UNIversal, Orthogonal Network (UNION) bioinks. As demonstration of UNION bioink versatility, gelatin, hyaluronic acid (HA), recombinant elastin-like protein (ELP), and polyethylene glycol (PEG) are each used as backbone polymers to create inks with storage moduli spanning from 200 to 10 000 Pa. Because UNION bioinks are crosslinked by a common chemistry, multiple materials can be printed together to form a unified, cohesive structure. This approach is compatible with any support bath that enables diffusion of UNION crosslinkers. Both matrix-adherent human corneal mesenchymal stromal cells and non-matrix-adherent human induced pluripotent stem cell-derived neural progenitor spheroids are printed with UNION bioinks. The cells retained high viability and expressed characteristic phenotypic markers after printing. Thus, UNION bioinks are a versatile strategy to expand the toolkit of customizable materials available for 3D bioprinting.     

Mechanical Gradient Cues for Guided Cell Motility and Control of Cell Behavior on Uniform Substrates

A novel method for the fabrication and the use of simple uniform poly(dimethylsiloxane) PDMS substrates for controlling cell motility by a mechanical gradient is reported. The substrate is fabricated in PDMS using soft lithography and consists of a soft membrane suspended on top of a patterned PDMS substrate. The difference in the gradient stiffness is related to the underlying pattern. It is shown experimentally that these uniform substrates can modulate the response of cell motility, thus enabling patterning on the surfaces with precise cell motility. Because of the uniformity of the substrate, cells can spread equally and a directional movement to stiffer regions is clearly observed. Varying the geometry underlying the membrane, cell patterning and movement can be quantitatively characterized. This procedure is capable of controlling cell motility with high fidelity over large substrate areas. The most significant advance embodied in this method is that it offers the use of mechanical features to control cell adhesion and not topographical or chemical variations, which has not been reported so far. This modulation of the response of cell motility will be useful for the design and fabrication of advanced planar and 3D biological assemblies suitable for applications in the field of biotechnology and for tissue‐engineering purposes.