scholarly journals Parametric Study of Jet/Droplet Formation Process during LIFT Printing of Living Cell-Laden Bioink

Micromachines ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 1408
Author(s):  
Christina Kryou ◽  
Ioannis Theodorakos ◽  
Panagiotis Karakaidos ◽  
Apostolos Klinakis ◽  
Antonios Hatziapostolou ◽  
...  
Keyword(s):  
Formation Process ◽  
Imaging System ◽  
Three Dimensional ◽  
Droplet Formation ◽  
Layer By Layer ◽  
Time Resolved ◽  
Wide Range ◽  
Cell Concentrations ◽  
Living Tissues ◽  
Uniform Droplets

Bioprinting offers great potential for the fabrication of three-dimensional living tissues by the precise layer-by-layer printing of biological materials, including living cells and cell-laden hydrogels. The laser-induced forward transfer (LIFT) of cell-laden bioinks is one of the most promising laser-printing technologies enabling biofabrication. However, for it to be a viable bioprinting technology, bioink printability must be carefully examined. In this study, we used a time-resolved imaging system to study the cell-laden bioink droplet formation process in terms of the droplet size, velocity, and traveling distance. For this purpose, the bioinks were prepared using breast cancer cells with different cell concentrations to evaluate the effect of the cell concentration on the droplet formation process and the survival of the cells after printing. These bioinks were compared with cell-free bioinks under the same printing conditions to understand the effect of the particle physical properties on the droplet formation procedure. The morphology of the printed droplets indicated that it is possible to print uniform droplets for a wide range of cell concentrations. Overall, it is concluded that the laser fluence and the distance of the donor–receiver substrates play an important role in the printing impingement type; consequently, a careful adjustment of these parameters can lead to high-quality printing.

Predictive Modeling of Droplet Formation Processes in Inkjet-Based Bioprinting

2018 ◽  
Vol 140 (10) ◽  
Author(s):  
Dazhong Wu ◽  
Changxue Xu
Keyword(s):  
Predictive Models ◽  
Formation Process ◽  
Imaging System ◽  
Polymer Concentration ◽  
Three Dimensional ◽  
Droplet Formation ◽  
Droplet Velocity ◽  
Coefficient Of Determination ◽  
Data Driven Approach ◽  
Living Tissues

Additive manufacturing is driving major innovations in many areas such as biomedical engineering. Recent advances have enabled three-dimensional (3D) printing of biocompatible materials and cells into complex 3D functional living tissues and organs using bio-printable materials (i.e., bioink). Inkjet-based bioprinting fabricates the tissue and organ constructs by ejecting droplets onto a substrate. Compared with microextrusion-based and laser-assisted bioprinting, it is very difficult to predict and control the droplet formation process (e.g., droplet velocity and volume). To address this issue, this paper presents a new data-driven approach to predicting droplet velocity and volume in the inkjet-based bioprinting process. An imaging system was used to monitor the droplet formation process. To investigate the effects of polymer concentration, excitation voltage, dwell time, and rise time on droplet velocity and volume, a full factorial design of experiments (DOE) was conducted. Two predictive models were developed to predict droplet velocity and volume using ensemble learning. The accuracy of the two predictive models was measured using the root-mean-square error (RMSE), relative error (RE), and coefficient of determination (R2). Experimental results have shown that the predictive models are capable of predicting droplet velocity and volume with sufficient accuracy.

Predictive Modeling of Droplet Velocity and Size in Inkjet-Based Bioprinting

2018 ◽  
Author(s):  
Dazhong Wu ◽  
Changxue Xu ◽  
Srikumar Krishnamoorthy
Keyword(s):  
Droplet Size ◽  
Predictive Models ◽  
Formation Process ◽  
Imaging System ◽  
Droplet Formation ◽  
Droplet Velocity ◽  
Data Driven Approach ◽  
Factorial Design Of Experiments ◽  
Living Tissues ◽  
And Control

Additive manufacturing is driving major innovations in many areas such as biomedical engineering. Recent advances have enabled 3D printing of biocompatible materials and cells into complex 3D functional living tissues and organs using bioink. Inkjet-based bioprinting fabricates the tissue and organ constructs by ejecting droplets onto a substrate. Compared with microextrusion-based and laser-assisted bioprinting, it is very difficult to predict and control the droplet formation process (e.g., droplet velocity and size). To address this issue, this paper presents a new data-driven approach to predict droplet velocity and size in the inkjet-based bioprinting process. An imaging system was used to monitor the droplet formation process. To investigate the effects of excitation voltage, dwell time, and rise time on droplet velocity and droplet size, a full factorial design of experiments was conducted. Two predictive models were developed to predict droplet velocity and droplet size using random forests. The accuracy of the two predictive models was evaluated using the relative error. Experimental results have shown that the predictive models are capable of predicting droplet velocity and size with sufficient accuracy.

A Robust True Direct-Print Technology for Tissue Engineering

2007 ◽  
Author(s):  
B. Li ◽  
T. Dutta Roy ◽  
C. M. Smith ◽  
P. A. Clark ◽  
K. H. Church
Keyword(s):  
Tissue Engineering ◽  
Computer Aided Design ◽  
Fused Deposition Modeling ◽  
Three Dimensional ◽  
Layer By Layer ◽  
Fused Deposition ◽  
Wide Range ◽  
Computer Aided ◽  
Liquid Material ◽  
Print Process

Numerous solid freeform fabrication (SFF) or rapid prototyping (RP) techniques have been employed in the field of tissue engineering to fabricate specially organized three-dimensional (3-D) structures such as scaffolds. Some such technologies include, but are not limited to, laminated object manufacturing (LOM), three-dimensional printing (3-DP) or ink-jet printing, selective laser sintering (SLS), and fused deposition modeling (FDM). These techniques are capable of rapidly producing highly complex 3-D scaffolds or other biomedical structures with the aid of a computer-aided design (CAD) system. However, they suffer from lack of consistency and repeatability, since most of these processes are not fully controlled and cannot reproduce the previous work with accuracy. Also, these techniques (excluding FDM) are not truly direct-print processes. Certain material removing steps are involved, which in turn increases the complexity and the cost of fabrication. The FDM process has good repeatability; however, the materials that can be used are limited due to the high temperature needed to melt the feedstock. Some researchers also reported that the scaffolds fabricated by FDM lack consistency in the z-direction. In this paper, we will present a true direct-print technology for repeatedly producing scaffolds and other biomedical structures for tissue engineering with the aid of our Computer Aided Biological (CAB) tool. Unlike other SFF techniques mentioned above, our direct-print process fabricates scaffolds or other complex 3-D structures by extruding (dispensing) a liquid material onto the substrate with a prescribed pattern generated by a CAD program. This can be a layer-by-layer 2.5 dimension build or a true 3-D build. The dispensed liquid material then polymerizes or solidifies, to form a solid structure. The flexibility in the types of materials that can be extruded ranges from polymers to living cells, encapsulated in the proper material. True 3-D structures are now possible on a wide range of substrates, including even in vivo. Some of the advantages of the process are a) researchers have full control over the patterns to be created; b) it is a true direct-print process with no material removing steps involved; c) it is highly consistent and repeatable; and d) it is highly efficient and cost-effective. This paper will first give a detailed description of the CAB tool. Then, it will present a detailed process for printing polycaprolactone (PCL) into a defined 3-D architecture, where the primary focus for these constructs is for use in tissue engineering applications. Finally, mechanical characterization results of the printed scaffolds will be included in the paper.

scholarly journals Extended mechanical force measurements using structured illumination microscopy

2021 ◽  
Vol 379 (2199) ◽  
Author(s):  
Kseniya Korobchevskaya ◽  
Huw Colin-York ◽  
Liliana Barbieri ◽  
Marco Fritzsche
Keyword(s):  
Imaging System ◽  
Three Dimensional ◽  
Traction Force ◽  
Super Resolution ◽  
Mechanical Force ◽  
Structured Illumination ◽  
Structured Illumination Microscopy ◽  
Biological Studies ◽  
Wide Range ◽  
Spatio Temporal

Quantifying cell generated mechanical forces is key to furthering our understanding of mechanobiology. Traction force microscopy (TFM) is one of the most broadly applied force probing technologies, but its sensitivity is strictly dependent on the spatio-temporal resolution of the underlying imaging system. In previous works, it was demonstrated that increased sampling densities of cell derived forces permitted by super-resolution fluorescence imaging enhanced the sensitivity of the TFM method. However, these recent advances to TFM based on super-resolution techniques were limited to slow acquisition speeds and high illumination powers. Here, we present three novel TFM approaches that, in combination with total internal reflection, structured illumination microscopy and astigmatism, improve the spatial and temporal performance in either two-dimensional or three-dimensional mechanical force quantification, while maintaining low illumination powers. These three techniques can be straightforwardly implemented on a single optical set-up offering a powerful platform to provide new insights into the physiological force generation in a wide range of biological studies. This article is part of the Theo Murphy meeting issue ‘Super-resolution structured illumination microscopy (part 1)'.

scholarly journals Simultaneous measurements of three-dimensional trajectories and wingbeat frequencies of birds in the field

2018 ◽  
Vol 15 (147) ◽  
pp. 20180653 ◽  
Author(s):  
Hangjian Ling ◽  
Guillam E. Mclvor ◽  
Geoff Nagy ◽  
Sepehr MohaimenianPour ◽  
Richard T. Vaughan ◽  
...  
Keyword(s):  
Stereo Matching ◽  
Imaging System ◽  
Three Dimensional ◽  
Bird Species ◽  
Three Dimensions ◽  
Natural Environments ◽  
Flight Performance ◽  
Stereo Imaging ◽  
Wingbeat Frequency ◽  
Wide Range

Tracking the movements of birds in three dimensions is integral to a wide range of problems in animal ecology, behaviour and cognition. Multi-camera stereo-imaging has been used to track the three-dimensional (3D) motion of birds in dense flocks, but precise localization of birds remains a challenge due to imaging resolution in the depth direction and optical occlusion. This paper introduces a portable stereo-imaging system with improved accuracy and a simple stereo-matching algorithm that can resolve optical occlusion. This system allows us to decouple body and wing motion, and thus measure not only velocities and accelerations but also wingbeat frequencies along the 3D trajectories of birds. We demonstrate these new methods by analysing six flocking events consisting of 50 to 360 jackdaws ( Corvus monedula ) and rooks ( Corvus frugilegus ) as well as 32 jackdaws and 6 rooks flying in isolated pairs or alone. Our method allows us to (i) measure flight speed and wingbeat frequency in different flying modes; (ii) characterize the U-shaped flight performance curve of birds in the wild, showing that wingbeat frequency reaches its minimum at moderate flight speeds; (iii) examine group effects on individual flight performance, showing that birds have a higher wingbeat frequency when flying in a group than when flying alone and when flying in dense regions than when flying in sparse regions; and (iv) provide a potential avenue for automated discrimination of bird species. We argue that the experimental method developed in this paper opens new opportunities for understanding flight kinematics and collective behaviour in natural environments.

Robust Direct-Write Dispensing Tool and Solutions for Micro/Meso-Scale Manufacturing and Packaging

2007 ◽  
Author(s):  
B. Li ◽  
P. A. Clark ◽  
K. H. Church
Keyword(s):  
Vapor Deposition ◽  
Physical Vapor Deposition ◽  
Time Pressure ◽  
Three Dimensional ◽  
Chemical Vapor ◽  
Volume Control ◽  
Layer By Layer ◽  
Micro Fabrication ◽  
Wide Range ◽  
Meso Scale

The development of functional and reliable miniaturized devices including Micro Electro Mechanical Systems (MEMS) has stressed the manufacturing and packaging processes. The traditional micro fabrication techniques, such as lithography, physical vapor deposition (PVD), chemical vapor deposition (CVD) and etching, are layer-by-layer processes and mostly suitable for thin-filmed devices. LIGA (an acronym from German words for lithography, electroplating, and molding) is a newly developed process for thick metallic devices; however, it involves electroplating process and high quality molds, which are hard to move after electroforming. In all the processes mentioned above, masks and photoresist processing are inevitable, which complicates the whole process and increases the processing time and the total cost. It is also well known that packaging is another barrier for the advancement of MEMS. MEMS packaging, which is required to provide mechanical support, environmental protection and electrical connection to other system components, is much more complicated as compared to electronic components due to the moving structures, fluids or chemicals involved. It is the most expensive process in micromachining. Therefore, enabling tools and technologies are greatly needed for the fabrication and packaging of complicated devices and highly integrated micro assemblies. In this paper, we will present novel direct-print dispensing techniques and robust tools for 21st century manufacturing and packaging. Comparing to other dispensing technologies such as time-pressure needle dispensing, screen printing, pin transfer and jetting, nScrypt’s pumping techniques can dispense materials with precise volume control for 10’s of Pico liter resolution, accurate placement or alignment within a few microns, conformably print on exaggerated surfaces of 10’s of centimeters, and are extremely flexible with materials and patterns. The dispensing tip (nozzle) is optimized to reduce the pressure drop as compared to the traditional tubing needles. Comparing to traditional micro fabrication technologies, our direct-print dispensing technology is maskless and thus a cost effective process. While micro-dispensing is a solution based approach, it has the advantage of not being a wet process such as wet etching or electroplating. Direct-print dispensing of micro lines, micro dots, and three-dimensional structures will be presented. The technology has a wide range of applications in the manufacturing and packaging of micro/meso-scale devices and bio structures.

Time-resolved evolution of coherent structures in turbulent channels: characterization of eddies and cascades

2014 ◽  
Vol 759 ◽  
pp. 432-471 ◽  
Author(s):  
Adrián Lozano-Durán ◽  
Javier Jiménez
Keyword(s):  
Turbulent Flows ◽  
Coherent Structures ◽  
Three Dimensional ◽  
Time Resolved ◽  
Novel Approach ◽  
Wide Range ◽  
Self Similar ◽  
Logarithmic Layer ◽  
Advection Velocity

AbstractA novel approach to the study of the kinematics and dynamics of turbulent flows is presented. The method involves tracking in time coherent structures, and provides all of the information required to characterize eddies from birth to death. Spatially and temporally well-resolved DNSs of channel data at $\mathit{Re}_{{\it\tau}}=930{-}4200$ are used to analyse the evolution of three-dimensional sweeps, ejections (Lozano-Durán et al., J. Fluid Mech., vol. 694, 2012, pp. 100–130) and clusters of vortices (del Álamo et al., J. Fluid Mech., vol. 561, 2006, pp. 329–358). The results show that most of the eddies remain small and do not last for long times, but that some become large, attach to the wall and extend across the logarithmic layer. The latter are geometrically and temporally self-similar, with lifetimes proportional to their size (or distance from the wall), and their dynamics is controlled by the mean shear near their centre of gravity. They are responsible for most of the total momentum transfer. Their origin, eventual disappearance, and history are investigated and characterized, including their advection velocity at different wall distances and the temporal evolution of their size. Reinforcing previous results, the symmetry found between sweeps and ejections supports the idea that they are not independent structures, but different manifestations of larger quasi-streamwise rollers in which they are embedded. Spatially localized direct and inverse cascades are respectively associated with the splitting and merging of individual structures, as in the models of Richardson (Proc. R. Soc. Lond. A, vol. 97(686), 1920, pp. 354–373) or Obukhov (Izv. Akad. Nauk USSR, Ser. Geogr. Geofiz., vol. 5(4), 1941, pp. 453–466). It is found that the direct cascade predominates, but that both directions are roughly comparable. Most of the merged or split fragments have sizes of the order of a few Kolmogorov viscous units, but a substantial fraction of the growth and decay of the larger eddies is due to a self-similar inertial process in which eddies merge and split in fragments spanning a wide range of scales.

scholarly journals Progress of 3D Bioprinting in Organ Manufacturing

Polymers ◽  
2021 ◽  
Vol 13 (18) ◽  
pp. 3178
Author(s):  
Dabin Song ◽  
Yukun Xu ◽  
Siyu Liu ◽  
Liang Wen ◽  
Xiaohong Wang
Keyword(s):  
Computer Aided Design ◽  
Three Dimensional ◽  
Research Progress ◽  
Layer By Layer ◽  
3D Bioprinting ◽  
Bioartificial Organs ◽  
Computer Aided ◽  
Bioactive Agents ◽  
Living Tissues ◽  
Aided Design

Three-dimensional (3D) bioprinting is a family of rapid prototyping technologies, which assemble biomaterials, including cells and bioactive agents, under the control of a computer-aided design model in a layer-by-layer fashion. It has great potential in organ manufacturing areas with the combination of biology, polymers, chemistry, engineering, medicine, and mechanics. At present, 3D bioprinting technologies can be used to successfully print living tissues and organs, including blood vessels, skin, bones, cartilage, kidney, heart, and liver. The unique advantages of 3D bioprinting technologies for organ manufacturing have improved the traditional medical level significantly. In this article, we summarize the latest research progress of polymers in bioartificial organ 3D printing areas. The important characteristics of the printable polymers and the typical 3D bioprinting technologies for several complex bioartificial organs, such as the heart, liver, nerve, and skin, are introduced.

scholarly journals Characterization of 3-Dimensional Printing and Casting Materials for use in Computed Tomography and X-ray Imaging Phantoms

2020 ◽  
Vol 125 ◽  
Author(s):  
B. E. Yunker ◽  
A. Holmgren ◽  
K. F. Stupic ◽  
J. L. Wagner ◽  
S. Huddle ◽  
...  
Keyword(s):  
Computed Tomography ◽  
3D Printing ◽  
Imaging System ◽  
Three Dimensional ◽  
3D Printer ◽  
Attenuation Coefficients ◽  
X Ray ◽  
Fused Deposition ◽  
Imaging Phantoms ◽  
Wide Range

Imaging phantoms are used to calibrate and validate the performance of medical computed tomography (CT) systems. Many new materials developed for three-dimensional (3D) printing processes may be useful in the direct printing or casting of biomimetic and geometrically accurate CT and X-ray phantoms. The X-ray linear attenuation coefficients of polymer samples were measured to discover materials for use as tissue mimics in phantoms. This study included a cohort of polymer compounds that were tested in cured form. The cohort consisted of 101 standardized polymer samples fabricated from: two-part silicones and polyurethanes used in commercial casting processes; one-part optically cured polyurethanes used in 3D printing; and fused deposition thermoplastics used in 3D printing. The testing was performed with a commercial micro-CT imaging system from 40 kVp to 140 kVp. The X-ray linear coefficients of the samples and human tissues were plotted with error bars to allow the reader to identify suitable mimics. The X-ray linear attenuation coefficients of the tested material samples spanned a wide range of values, with a small number of them overlapping established human tissue mimic values. Twenty 3D printer materials and one castable polyurethane tracked nylon and polymethyl methacrylate (PMMA) as established X-ray mimics for fat. Five 3D printer materials tracked water as an established X-ray mimic for muscle.

A Numerical Investigation of Thermally Mediated Droplet Formation in a T-Junction

2009 ◽  
Author(s):  
Peng-Ching Ho ◽  
Yit Fatt Yap ◽  
Nam-Trung Nguyen ◽  
John Chai Chee Kiong ◽  
Teck Neng Wong ◽  
...  
Keyword(s):  
Surface Tension ◽  
Numerical Investigation ◽  
Present Article ◽  
Formation Process ◽  
Three Dimensional ◽  
Droplet Formation ◽  
Navier Stokes ◽  
Thermal Forcing ◽  
Two Phase ◽  
Interfacial Conditions

The present article presents a numerical investigation on the effect of thermal forcing for droplet formation in a T-junction. Thermal forcing, generated by a heater embedded into the channel wall, induces a non-uniform temperature field which results in the variation the fluids’ properties and affects the droplet formation process in a desirable manner. In the present article, droplet formation process is posed as an incompressible immiscible two-phase flow problem with the motion of the two-phases strongly coupled via the related interfacial conditions. It is governed by the three-dimensional Navier-Stokes and the energy equations. The interface is captured with a narrow-band particle level-set method. Solutions are obtained using a finite volume method on a staggered mesh. The numerical model is validated against droplet formation in a cross junction. With the formation of water droplet in oil within the squeezing formation regime as a case study, the physics underlying droplet formation process in a T-junction affected by a thermal forcing is investigated. The combined effect of variations in both viscosities and surface tension result in a larger droplet. It is believed that the behavior of fluids system under an imposed thermal forcing depends strongly on the characteristics of temperature dependent viscosities and surface tension.

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