| Photocuring printing technique cures polymer monomer layer by layer at a specific wavelength of ultraviolet light.As a 3D printing technology with high precision and efficient,it has wide application in the field of medication.However,internal and external structures have different requirements for printing material and process parameters.So far,there has been a lack of systematic comparison and study on the photocurable printability of internal and external structures was necessary.In this study,the effect of printing material and process parameters on the printability of internal and external structures was evaluated using biocompatible polymer as photocurable monomer.The possibility to print personalized drug-loaded implants and physiological channels by photocuring printing technique was also evaluated.The effects of printing material on the formability,printing accuracy,and mechanical properties of 3D models with internal and external structures were evaluated using poly(ethylene glycol)diacrylate(PEGDA)as photocuring monomer.The results showed that the addition of photoabsorber promoted the formability of internal structure.When tartrazine concentration was 0.25 mg/m L,the patency degree of internal vertical channel(?=1.5 mm)was the highest(64.4%).Besides,PEGDA concentration had different effect on the printability of models with fine internal and external structures.When PEGDA concentration was 100%,the printing height of convex cone(? =1.0 mm)was the highest(2.53 mm).Therefore,the optimal printing material for external structure(Rx-I)was 100%PEGDA.When PEGDA concentration was 75% and tartrazine concentration was 0.25 mg/m L,the printing accuracy and integrity of internal vertical and horizontal channels were the best.Therefore,the optimal printing material for internal structure(Rx-?)was 75%PEGDA with 0.25 mg/m L tartrazine.Furthermore,as a plasticizer,PEG300 affected both the printing accuracy and mechanical properties of the printed samples.When 20% PEG300 was added,the printing height of convex cone(?=1.0 mm)was the highest(2.58 mm).And the mechanical strength and ductility(tensile strength was 6.3 MPa,elongation at break was 10.5%)were suitable for preparing implants.Therefore,the optimal printing material for implants(Rx-?)was PEGDA: PEG300 = 80:20.Influence of printing parameters on printing accuracy,curing degree and printing efficiency of external and internal structures were evaluated based on the above optimal printing materials.It was found that layer height had different influence on the printability of external and internal structures.When the layer height was 0.02 mm,the printing height of convex cone(?=0.75 mm)was the largest(2.36 mm).When the layer height was 0.05 mm,both horizontal channel(?=1.0 mm)and vertical channel(?=1.0 mm)had the highest patency degree(both was 100%).Exposure time greatly affected the sample adhesion and the curing degree.When the exposure time at bottom was 30-90 s,printed sample(cylinder with a height of 6.0 mm)had good adhesion to the printing platform,and no sample fell off the platform during printing.To ensure the complete printing,the optimal exposure time at bottom was 60 s.When the exposure time of other layers was 4-12 s,the printed samples had high curing degree.However,with a longer exposure time,the printing time significantly prolonged and the sample hardness also increased.Considering the printing efficiency and sample strength,the exposure time of other layers was optimized to be 8s.Printed at the optimal conditions,the cuboid printed with Rx-I had a weight of 166 mg and a hardness of 106.8 N,whereas the cuboid printed with Rx-? had a weight of 144.8 mg and a hardness of 28.4 NUsing Rx-? as printing material,and diclofenac sodium or ibuprofen as model drug,implants with different shapes were printed to evaluate the appearance,biomechanical behavior and in vitro dissolution behavior.It was found that implants with different shapes had good appearance.The typical U-shaped and arc-shaped samples had good strength and elasticity with a surface compression,and the deformation recovered after removing the compression.The biomechanical simulation suggested that the simulated maximum stress and strain of typical U-shaped and arc-shaped samples appeared at the bottom and upper surface,respectively.The simulation results proved that the mechanical properties of the typical implants were good enough to guarantee the integrity of implants under pressure.Furthermore,implants were printed by adding 10% soluble drug diclofenac sodium or 10% slightly soluble drug ibuprofen into the printing materials.The printability and drug loading ability of implants with different shapes were proved.Diclofenac sodium loaded implants exhibited 24 h sustained-release properties,and the cumulative release percentage at 24 h were: 86.3% for needle-shaped sample,78.8% for T-shaped sample,87.9% for ring-shaped sample,83.7% for U-shaped and 85.0% for arc-shaped sample.The in vitro release of ibuprofen implants could last for several days,and the cumulative release percentage at 24 h were: needle-shaped for 102.6%,T-shaped for 47.2%,ring-shaped for 70.1%,U-shaped for 74.2% and arc-shaped for 71.8%.Using Rx-? as printing material,samples with different internal channels were printed to evaluate the structural integrity and fluid dynamics of internal channels.The results showed that the printed samples with internal channels(vascular model,tracheal model and fluid mixing model)had good appearance and integrity structure.The fluid dynamics simulation was conducted using typical fluid mixing model.The simulated total pressure decreased along the fluid field from the inlet(212 Pa)to the outlet(1.3 Pa).The simulated turbulent intensity distribution was non-uniform and the maximum turbulent intensity appeared at the intersection of two liquids.The fluid velocity distribution was also non-uniform,and the maximum velocity appeared in the flow field where two liquids mixed together.In this study,the photocuring printability of internal and external structures was compared,while drug-loaded implants and physiological channels were prepared using optimal printing materials and parameters.The results of this study could provide experimental basis for the preparation of drug-loaded implants and simplified physiological channels. |
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