Fabrication of Gellan Gum Tubular Structure Using Coaxial Needles: A Study on Wall Thickness and Encapsulation

2018 ◽  
Author(s):  
Ilhan Yu ◽  
Roland Chen ◽  
Samantha Grindrod
Keyword(s):  
Wall Thickness ◽  
Rate Ratio ◽  
Gellan Gum ◽  
Flow Rate Ratio ◽  
Tubular Structures ◽  
Extrusion Speed ◽  
Extrusion Rate ◽  
Coaxial Needle ◽  
Thermal Crosslinking ◽  
Phosphate Buffered Saline

Tubular structures of hydrogel are used in a variety of applications such as 3D cell culturing for delivery of nutrient supplies. The wall thickness of the tube determines the speed of diffusion or delivery rate. In this study, we aimed to fabricate tubular structures with varying of wall thicknesses using a thermal-crosslinking hydrogel, gellan gum, with the coaxial needle approach. The wall thickness is controlled by changing the flow rate ratio between the inner (phosphate-buffered saline) and outer needles (gellan gum). A simulation model was developed to estimate the proper extrusion speed to allow the gellan gum to be extruded around its glass transition temperature. While keeping the extrusion rate of gellan gum fixed, different PBS extrusion rates were tested to investigate the printability to form continuous tubular structures, range of printable wall thickness, and possibility to form tubes with closed ends to encapsulate fluid or drug inside the tube. The ranges of printable wall thickness with two pairs of coaxial needle were identified. It was found that at about 200% of the baseline PBS extrusion speed, a maximum of 20% difference in wall thickness can be achieved, while a close end can still be formed.

Controllability Over Wall Thickness of Tubular Structures and Encapsulation During Co-Axial Extrusion of a Thermal-Crosslinking Hydrogel

2020 ◽  
Vol 142 (8) ◽  
Author(s):  
Ilhan Yu ◽  
Samantha Grindrod ◽  
Roland Chen
Keyword(s):  
Flow Velocity ◽  
Wall Thickness ◽  
Dynamic Viscosity ◽  
Element Model ◽  
Extrusion Process ◽  
Tubular Structures ◽  
Needle Size ◽  
Thermal Crosslinking ◽  
Outer Needle ◽  
Phosphate Buffered Saline

Abstract Tubular structures of the hydrogel are used in a variety of applications such as delivering nutrient supplies for 3D cell culturing. The wall thickness of the tube determines the delivery rate. In this study, we used the coaxial extrusion process to fabricate tubular structures with varying wall thicknesses using a thermal-crosslinking hydrogel, gellan gum (GG). The objectives of this study are to investigate the thermal extrusion process of GG to form tubular structures, the range of achievable wall thickness, and a possibility to form tubular structures with closed ends to encapsulate fluid or drug inside the tube. The wall thickness is controlled by changing the relative flow velocity of the inner needle (phosphate-buffered saline, PBS) to the outer needle, while keeping the velocity of outer needles (GG) constant. Two pairs of coaxial needles were used which are 18-12 gauge (G) and 20-12G. The controllable wall thickness ranges from 0.618 mm (100% relative velocity) to 0.499 mm (250%) for 18-12G and from 0.77 mm (80%) to 0.69 (200%) for 20-12G. Encapsulation is possible in a smaller range of flow velocities in both needle combinations. A finite element model was developed to estimate the temperature distribution and the wall thickness. The model is found to be accurate. The dynamic viscosity of GG determines the pressure equilibrium and the range of achievable wall thickness. Changing the inner needle size or the flow velocity both affect the heat exchange and thus the temperature-dependent dynamic viscosity.

Formation of a Hollow Jet and its Breakup in Ambient Air

2011 ◽  
Author(s):  
Truong V. Vu ◽  
Hideyuki Takakura ◽  
John C. Wells ◽  
Takashi Minemoto
Keyword(s):  
Wall Thickness ◽  
Flow Rate ◽  
Weber Number ◽  
Rate Ratio ◽  
Ambient Air ◽  
Flow Rate Ratio ◽  
Drop Formation ◽  
Satellite Formation ◽  
Argon Gas ◽  
Water Jets

An experiment investigation on the formation and breakup of a hollow jet issuing from a coaxial nozzle into ambient air has been carried out. The hollow jet consists of an outer jet of water that encloses an inner jet of argon gas. By varying the flow rate ratio of the inner jet to the outer jet, three different breakup patterns of hollow water jets are identified using two types of nozzles: (I) satellite formation, (II) single-core hollow drop formation, and (III) multi-core hollow drop formation. These patterns are mapped in a space of Weber number versus flow rate ratio, We – Q. Experimental results in pattern (II) show that increasing the flow rate ratio results in increasing the formation frequency, slightly increasing outer diameters of the hollow drops, and decreasing their wall thickness.

Determination of flow rate ratio for plate valve operating in two-phase medium

1989 ◽  
Vol 25 (7) ◽  
pp. 394-396
Author(s):  
V. E. Shcherba ◽  
I. S. Berezin ◽  
S. S. Danilenko ◽  
I. E. Titov ◽  
P. P. Filippov
Keyword(s):  
Flow Rate ◽  
Rate Ratio ◽  
Flow Rate Ratio ◽  
Two Phase ◽  
Plate Valve ◽  
Phase Medium

Effect of the argon/monomer flow-rate ratio on the flowability trend of PECVD-processed micropowder

2017 ◽  
Vol 328 ◽  
pp. 480-487 ◽  
Author(s):  
V.R. Giampietro ◽  
M. Gulas ◽  
P. Rudolf von Rohr
Keyword(s):  
Flow Rate ◽  
Rate Ratio ◽  
Flow Rate Ratio

Effects of Respiration and Gravity on Infradiaphragmatic Venous Flow in Normal and Fontan Patients

Circulation ◽  
2000 ◽  
Vol 102 (suppl_3) ◽  
Author(s):  
Tain-Yen Hsia ◽  
Sachin Khambadkone ◽  
Andrew N. Redington ◽  
Francesco Migliavacca ◽  
John E. Deanfield ◽  
...  
Keyword(s):  
Flow Rate ◽  
Rate Ratio ◽  
Venous Return ◽  
Fontan Circulation ◽  
Flow Rate Ratio ◽  
Venous Flow ◽  
Beneficial Effects ◽  
In Series ◽  
Expiratory Flow ◽  
Fontan Patients

Background —In the Fontan circulation, pulmonary and systemic vascular resistances are in series. The implications of this unique arrangement on infradiaphragmatic venous physiology are poorly understood. Methods and Results —We studied the effects of respiration and gravity on infradiaphragmatic venous flows in 20 normal healthy volunteers (control) and 48 Fontan patients (atriopulmonary connection [APC] n=15, total cavopulmonary connection [TCPC] n=30). Hepatic venous (HV), subhepatic inferior vena caval (IVC), and portal venous (PV) flow rates were measured with Doppler ultrasonography during inspiration and expiration in both the supine and upright positions. The inspiratory-to-expiratory flow rate ratio was calculated to reflect the effect of respiration, and the supine-to-upright flow rate ratio was calculated to assess the effect of gravity. HV flow depended heavily on inspiration in TCPC compared with both control and APC subjects (inspiratory-to-expiratory flow rate ratio 3.4, 1.7, and 1.6, respectively; P <0.0001). Normal PV flow was higher in expiration, but this effect was lost in TCPC and APC patients (inspiratory-to-expiratory flow rate ratio 0.8, 1.0, and 1.1, respectively; P =0.01). The respiratory influence on IVC flow was the same in all groups. Gravity decreased HV flow more in APC than in TCPC patients (supine-to-upright flow rate ratio 3.2 versus 2.1, respectively; P <0.04) but reduced PV flow equally in all groups. Conclusions —Gravity and respiration have important influences on infradiaphragmatic venous return in Fontan patients. Although gravity exerts a significant detrimental effect on lower body venous return, which is more marked in APC than in TCPC patients, the beneficial effects of respiration in TCPC patients are mediated primarily by an increase in HV flow. These effects may have important short- and long-term implications for the hemodynamics of the Fontan circulation.

scholarly journals Numerical and experimental investigation on the depressurization capacity of a new type of depressure-dominated jet mill bit

2020 ◽  
Vol 17 (6) ◽  
pp. 1602-1615
Author(s):  
Xu-Yue Chen ◽  
Tong Cao ◽  
Kai-An Yu ◽  
De-Li Gao ◽  
Jin Yang ◽  
...  
Keyword(s):  
Flow Rate ◽  
Rate Ratio ◽  
Area Ratio ◽  
Low Flow ◽  
Flow Rate Ratio ◽  
Cuttings Transport ◽  
Horizontal Drilling ◽  
Hole Cleaning ◽  
Bottom Hole ◽  
New Type

AbstractEfficient cuttings transport and improving rate of penetration (ROP) are two major challenges in horizontal drilling and extended reach drilling. A type of jet mill bit (JMB) may provide an opportunity to catch the two birds with one stone: not only enhancing cuttings transport efficiency but also improving ROP by depressuring at the bottom hole. In this paper, the JMB is further improved and a new type of depressure-dominated JMB is presented; meanwhile, the depressurization capacity of the depressure-dominated JMB is investigated by numerical simulation and experiment. The numerical study shows that low flow-rate ratio helps to enhance the depressurization capacity of the depressure-dominated JMB; for both depressurization and bottom hole cleaning concern, the flow-rate ratio is suggested to be set at approximately 1:1. With all other parameter values being constant, lower dimensionless nozzle-to-throat-area ratio may result in higher depressurization capacity and better bottom hole cleaning, and the optimal dimensionless nozzle-to-throat-area ratio is at approximately 0.15. Experiments also indicate that reducing the dimensionless flow-rate ratio may help to increase the depressurization capacity of the depressure-dominated JMB. This work provides drilling engineers with a promising tool to improve ROP.

Numerical Simulation of Jetting Instability in Flow Focusing Microfluidics

2014 ◽  
Vol 609-610 ◽  
pp. 630-636
Author(s):  
Hong Bo Zhang ◽  
Jian Pu Liu ◽  
Huan Xin Lai
Keyword(s):  
Numerical Simulation ◽  
Surface Tension ◽  
Rate Ratio ◽  
Silicone Oil ◽  
Flow Rate Ratio ◽  
Absolute Instability ◽  
Flow Ratio ◽  
Flow Focusing ◽  
Immiscible Liquids ◽  
Main Factor

In this paper, jetting behavior of two immiscible liquids, water as the outer liquid and silicone oil as the inner liquid in typical flow focusing microchannels were numerically studied using VOF method. At low capillary number, uniform microdroplets were obtained by the absolute instability. With the increasing of fluid flow ratio, the jet is thinner and tends to break up further away the cross junction. The results showed that the flow rate ratio is the main factor that influences the microdroplet sizes, while the frequency of microdroplets formation can be controlled mainly by the surface tension when it is in the jetting regime.

The Characteristics of CH4-Vapor Catalytic Reforming Reaction Considering CO2 and CH4 Reaction in the Micro-Chamber

2007 ◽  
Author(s):  
Jing-Yu Ran ◽  
Li-Xiang Niu ◽  
Qiang Tang ◽  
Li Zhang
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Rate Ratio ◽  
Reaction System ◽  
Conversion Ratio ◽  
Flow Rate Ratio ◽  
Ni Catalyst ◽  
Complex Reaction ◽  
Catalytic Reforming

Methane and vapor catalytic-reaction is a complex reaction system, and especially CH4/CO2 reaction has an important influence to the methane/vapor reforming reaction. In this paper, the reaction character for methane and vapor catalytic reforming reaction in the micro-chamber wall with Ni catalyst is numerically investigated. The results show that the CH4/CO2 reaction has a vital influence on reactive characteristics in the different H2O/CH4 mole ratio and the mass flow-rate. With increasing the H2O/CH4 mole ratio, the concentration of H2 and CO2 increases, the concentration of CO increases and then decreases, but if the H2O/CH4 mole ratio is more than 2.5, the result is different. The reaction efficiency will descend while the flow-rate increases. The results also display that the methane conversion ratio, the vapor conversion ratio, and the hydrogen concentrations can be up to 81.73%, 69.42%, and 4.29%, while the H2O/CH4 mole ratio, flow-rate and methane/vapor mass flow-rate ratio are 2.5, 7 g/h and 0.1 respectively.

Effect of CS2 Flow Rate on the Formation of Aligned Carbon Microcoils

2019 ◽  
Vol 947 ◽  
pp. 40-46
Author(s):  
Hyun Ji Kim ◽  
Sung Hoon Kim
Keyword(s):  
Flow Rate ◽  
Vapor Deposition ◽  
Rate Ratio ◽  
Chemical Vapor ◽  
Regular Structure ◽  
Flow Rate Ratio ◽  
Total Flow ◽  
Total Flow Rate ◽  
Flow Rates ◽  
Thermal Chemical Vapor Deposition

The formation of aligned carbon microcoils could be achieved using C2H2 as a source gas and CS2 as an incorporated additive gas under thermal chemical vapor deposition system. To elucidate the ratio of C2H2/CS2 for the formation of the aligned carbon microcoils, the CS2 flow rate was first manipulated under the identical C2H2 flow rate (500sccm) condition. The formation and the alignment of carbon microcoils could be only achieved under the ratio of C2H2/CS2 = 33.3 condition, namely the flow rates of CS2 = 15sccm and C2H2= 500sccm. The total flow rate of the used gases was varied under the identical C2H2/CS2 flow rate ratio (33.3) condition. The C2H2 flow rate was manipulated under the identical CS2 flow rate (15sccm) condition. It was found that the formation and the alignment of carbon microcoils could be only achieved under the condition of 15sccm of CS2 flow rate in the range of 200 ~ 500sccm of C2H2 flow rate, regardless of the flow rate ratio of C2H2/CS2 and the total flow rate. The crystal structure of the well-aligned CMCs reveals the increase in the (002) peak in XRD spectrum for the aligned carbon microcoils, indicating the existence of the more regular structure in the aligned carbon microcoils. Based on these results, the cause for the formation of the aligned carbon microcoils only in the case of the CS2 flow rate = 15sccm with the imaginary pictures for the flow rate ratio of C2H2/CS2 just above the substrate were proposed.

Sign in / Sign up

Export Citation Format

Share Document