Page 164 - IJB-10-5

International Journal of Bioprinting Nozzle optimization for multi-ink bioprinting

Table 1. Viscosity characterization of sodium alginate 2.3.6. Novel design proposal of a single nozzle in
solutions. numerical simulation
A single nozzle with high switching efficiency was proposed
Concentration K (Pa·s ) n (-)
n
(wt%) based on numerical simulations. Initially, models of single
0.5 2.54 × 10 −2 0.25 nozzles with asymmetric shapes were prepared. A 1.0 wt%
SA solution was used on both sides of the conjunction area
1.0 0.169 0.64 to investigate which flow direction exhibited enhanced
2.0 0.589 0.76 switching efficiency. Based on these results, novel nozzle
designs were developed. Subsequently, 0.5 and 1.0 wt%
pressure, and the outlet pressure was atmospheric. After SA solutions flowed through these new nozzle designs to
configuring these settings, a case file was generated for evaluate Se.
OpenFOAM. InterFoam, a solver for multi-phase flow 2.4. Experimental procedures
within OpenFOAM, was employed for the subsequent
calculations. 2.4.1. Single nozzle preparation
The nozzles, each with a diameter of 1.5 mm, were
2.3.3. Evaluation method in numerical simulation fabricated using a vat polymerization-based 3D printer
In the numerical simulation, the ink (with viscosity shown (NOVA 3D Elfin 2, Shenzhen Nova Intelligent Technology
in Table 1) flowed from Inlet 1 at a rate of 2.71 × 10 Co., Shenzhen, China). These nozzles were constructed
−2
cm /s. The parameter α, as outlined in Equation (IX), was from photocurable clear plastic resin (NOVA3D High
3
analyzed in the conjunction area of the nozzle using the Transparency UV Resin, Shenzhen Nova Intelligent
numerical simulation. The t in the numerical simulation Technology Co., Shenzhen, China).
m
was defined as the moment when α reached 99%, as
illustrated in Figure 1C. 2.4.2. Setup of printing system
A 3D printing system (FLSUN-QQ-S, Zhengzhou Chaokuo
2.3.4. Effect of conjunction angle on switching Electronic Technology Co., Henan, China) equipped with
efficiency in numerical simulation a light source (λ = 450 nm) was used to print 3D hydrogel
The effect of the conjunction angle on Se was assessed structures. A single nozzle, fabricated as previously
41
through numerical simulations. 3D models of single described, was attached to this 3D printing system. In
nozzles with conjunction angles of 15°, 45°, 75°, and 90° this setup, SA-Ph ink containing 2.0 mM SPS and 1.0
were prepared. The conjunction angle was defined as mM Ru(bpy) was gelated through exposure to visible
3
the angle presented in Figure 1A. A 1.0 wt% SA solution light (λ = 450 nm). 3D structures consisting of several
flowed into the conjunction area of each nozzle, and t types of bioinks, including SA-Ph, the phenol derivative
m
was measured. Subsequently, Se was calculated using of hyaluronic acid and chitosan (hyaluronic acid-Ph and
Equation (II). chitosan-Ph, respectively), can be printed using the system
(Figure S3, Supporting Information).
2.3.5. Effect of viscosity on switching efficiency in
numerical simulation 2.4.3. Effect of conjunction angle on switching
The effect of viscosity on Se and the influence of conjunction efficiency in experiment
angles were evaluated via numerical simulations using The effect of the conjunction angle on Se was experimentally
single nozzles with angles of 15°, 45°, 75°, and 90°. Four analyzed to compare the experimental findings with results
combinations of different viscous SA solutions were tested from numerical simulations. Four types of nozzles with
angles of 15°, 45°, 75°, and 90° were prepared. Each bioink
as follows:
was sequentially extruded at a rate of 2.71 × 10 cm /s using
−2
3
1. A 0.5 wt% SA solution flowed against a 1.0 wt% SA a syringe pump, and the switching behavior was monitored
solution already present in the conjunction area. using a video camera. t was measured by analyzing
m
the video data, where t is the time taken for one ink to
2. A 1.0 wt% SA solution flowed against a 0.5 wt% SA completely fill the conjunction area, as shown in Figure 1D.
m
solution filled in the conjunction area. Se was calculated for each nozzle using Equation (II).
3. A 0.5 wt% SA solution flowed against a 2.0 wt% SA
solution filled in the conjunction area. 2.4.4. Effect of viscosity on switching efficiency
in experiment
4. A 2.0 wt% SA solution flowed against a 0.5 wt% SA For the analysis, 0.5, 1.0, and 2.0 wt% SA solutions, each
solution filled in the conjunction area. dyed either green or pink, were utilized. SA solutions

Volume 10 Issue 5 (2024) 156 doi: 10.36922/ijb.4091