Layer Manufacturing for in Vivo Devices

Design and development of model eye for retina laser by using additive manufacturing

Surgical skill of the surgeon can be improved by surgical simulation. Especially in ophthalmology, it is impossible to use real human/non-human primate eyes for ophthalmology surgery practice. However, surgical practice is most important for ophthalmologist. The retina laser surgery is one of the ophthalmology surgeries and it requires more surgical practice for surgeons to use the laser beam precisely to coagulate and fuse small areas of tissue. Dealing with the prospect of vision reduction or vision loss presents a peculiar problem and that can be highly stressful and frustrating for both doctors and patients. In this regard, training for indirect ophthalmoscopy and retinal photocoagulation is undergone using model eyes instead of real eyes. Properties and functioning of an existing model eye are huge and they differ from real human eye such as casings are completely rigid and focusing of retinal fundus is not completely covered. Therefore, this research concentrates to develop a model eye that assimilates close to the human eye by focussing on the maximum viewing area that is not done at the moment. Finally, the design and development of re-engineered model eye for retina laser is fabricated by additive manufacturing. Compared to existing plastic model eye, viewing area and viewing angle of the re-engineered model eye is increased by 16.66% and 6.14%, respectively. Due to design modifications and elimination of the insert, it can be reduced by 18.99% and 13.95% of height and weight of the top casing respectively. Developed re-engineered model eye will improve the surgical and diagnostic skill of the surgeon and increase their confidence and proficiency. It also augments the effective use of essential ophthalmic instruments. Additionally, it can reduce the surgical error and meet the existing demand of actual eyes for surgical practices.

Reverse engineering of complex biological body parts by squared distance enabled non-uniform rational B-spline technique and layered manufacturing

In tissue engineering, the successful modeling of scaffold for the replacement of damaged body parts depends mainly on external geometry and internal architecture in order to avoid the adverse effects such as pain and lack of ability to transfer the load to the surrounding bone. Due to flexibility in controlling the parameters, layered manufacturing processes are widely used for the fabrication of bone tissue engineering scaffold with the given computer-aided design model. This article presents a squared distance minimization approach for weight optimization of non-uniform rational B-spline curve and surface to modify the geometry that exactly fits into the defect region automatically and thus to fabricate the scaffold specific to subject and site. The study showed that though the errors associated in the B-spline curve and surface were minimized by squared distance method than point distance method and tangent distance method, the errors could be minimized further in the rational B-spline curve and surface as the optimal weight could change the shape that desired for the defect site. In order to measure the efficacy of the present approach, the results were compared with point distance method and tangent distance method in optimizing the non-rational and rational B-spline curve and surface fitting for the defect site. The optimized geometry then allowed to construct the scaffold in fused deposition modeling system as an example. The result revealed that the squared distance–based weight optimization of the rational curve and surface in making the defect specific geometry best fits into the defect region than the other methods used.

3D-Printable Biodegradable Polyester Tissue Scaffolds for Cell Adhesion

Additive manufacturing, or three-dimensional (3D) printing, has emerged as a viable technique for the production of vascularized tissue engineering scaffolds. In this report, a biocompatible and biodegradable poly(tri(ethylene glycol) adipate) dimethacrylate was synthesized and characterized for suitability in soft-tissue scaffolding applications. The polyester dimethacrylate exhibited highly efficient photocuring, hydrolyzability, and 3D printability in a custom microstereolithography system. The photocured polyester film demonstrated significantly improved cell attachment and viability as compared with controls. These results indicate promise of novel, printable polyesters for 3D patterned, vascularized soft-tissue engineering scaffolds.

Preparation of poly(ε-caprolactone)-based tissue engineering scaffolds by stereolithography

A photocrosslinkable poly(ε-caprolactone) (PCL)-based resin was developed and applied using stereolithography. No additional solvents were required during the structure preparation process. Three-armed PCL oligomers of varying molecular weights were synthesized, functionalized with methacrylic anhydride, and photocrosslinked, resulting in high gel content networks. Stereolithography was used to build designed porous scaffolds using the resin containing PCL macromer, Irgacure 369 photoinitiator, inhibitor and dye. A suitable resin viscosity was obtained by heating the resin during the curing process. The scaffolds precisely matched the computer-aided designs, with no observable material shrinkage. The average porosity was 70.5 ± 0.8%, and the average pore size was 465 μm. The pore network was highly interconnected. The photocrosslinkable, biodegradable PCL resin is well suited for the solvent-free fabrication of tissue engineering scaffolds by stereolithography.

Preparation of flexible and elastic poly(trimethylene carbonate) structures by stereolithography

3D porous and non-porous structures are designed and prepared by stereolithography using resins based on PTMC macromers. Tough, flexible network films prepared in this manner show E moduli of ≈3.8 MPa and high elongations at break >900%; tensile strengths are ≈4.2 MPa. These values increase with increasing PTMC macromer molecular weight. To reach suitable viscosities for processing, up to 45 wt% propylene carbonate is added as non-reactive diluent. The solid specimens have compression moduli of 3.1-4.2 MPa, similar to the values determined in tensile testing. The built porous structures show porosities of 53-66% and average pore sizes of 309-407 µm. The compression moduli of the porous structures are significantly lower than those of the solid structures.

Selective laser sintering of porous tissue engineering scaffolds from poly(L: -lactide)/carbonated hydroxyapatite nanocomposite microspheres

This study focuses on the use of bio-nanocomposite microspheres, consisting of carbonated hydroxyapatite (CHAp) nanospheres within a poly(L: -lactide) (PLLA) matrix, to produce tissue engineering (TE) scaffolds using a modified selective laser sintering (SLS) machine. PLLA microspheres and PLLA/CHAp nanocomposite microspheres were prepared by emulsion techniques. The resultant microspheres had a size range of 5-30 microm, suitable for the SLS process. Microstructural analyses revealed that the CHAp nanospheres were embedded throughout the PLLA microsphere, forming a nanocomposite structure. A custom-made miniature sintering platform was installed in a commercial Sinterstation((R)) 2000 SLS machine. This platform allowed the use of small quantities of biomaterials for TE scaffold production. The effects of laser power; scan spacing and part bed temperature were investigated and optimized. Finally, porous scaffolds were successfully fabricated from the PLLA microspheres and PLLA/CHAp nanocomposite microspheres. In particular, the PLLA/CHAp nanocomposite microspheres appeared to be promising for porous bone TE scaffold production using the SLS technique.

A review of rapid prototyping techniques for tissue engineering purposes

Rapid prototyping (RP) is a common name for several techniques, which read in data from computer-aided design (CAD) drawings and manufacture automatically three-dimensional objects layer-by-layer according to the virtual design. The utilization of RP in tissue engineering enables the production of three-dimensional scaffolds with complex geometries and very fine structures. Adding micro- and nanometer details into the scaffolds improves the mechanical properties of the scaffold and ensures better cell adhesion to the scaffold surface. Thus, tissue engineering constructs can be customized according to the data acquired from the medical scans to match the each patient's individual needs. In addition RP enables the control of the scaffold porosity making it possible to fabricate applications with desired structural integrity. Unfortunately, every RP process has its own unique disadvantages in building tissue engineering scaffolds. Hence, the future research should be focused on the development of RP machines designed specifically for fabrication of tissue engineering scaffolds, although RP methods already can serve as a link between tissue and engineering.