Enhanced Scaffold Fabrication Techniques for Optimal Characterization
Naznin Sultana, Sanchita Bandyopadhyay-Ghosh, Chin Fhong Soon in Tissue Engineering Strategies for Organ Regeneration, 2020
Selective laser sintering (SLS) applies powder bed fusion processes by using laser as an extreme heat source to sinter powder materials, Fig. 3.12. The powder will be melted and solidified layer-by-layer, eventually forming a 3D object. SLS printers are commonly equipped with two plates called pistons and a scanner system. In the beginning of the process, high power laser scans the first layer of powder that is laid onto the fabrication piston, selectively melting and sintering the powder material. Fabrication piston is moved lower after the first layer is solidified while the powder delivery bed is raised slightly to allow a roller to swipe another layer of powder on top of the previous solidified layer. This procedure is repeated to allow the laser to melt and solidify polymeric powder layer-by-layer, until the designed part has been finished bottom to top (Mazzoli 2013).
Poly(Alkyl Cyanoacrylate) Nanoparticles for Delivery of Anti-Cancer Drugs
Mansoor M. Amiji in Nanotechnology for Cancer Therapy, 2006
The methods used for the physicochemical characterization of nanoparticles are listed in Table 15.1. Particle size is the prominent feature of nanoparticles; the fastest and most routine methods of size analysis are photon correlation spectroscopy (PCS) and laser diffractometry (LD). The former method is useful for the determination of smaller particles,41 whereas the latter method is useful for the determination of larger particles. PCS determines the hydrodynamic diameter of the nanoparticles via Brownian motion. The electron microscopy methods also allow the exact particle determination. Scanning electron microscopy requires the coating of the dry sample with a conductive material such as gold. The gold coating usually results in an estimate of particle sizes that is slightly greater than the normal. TEM, with or without staining, is a relatively easier method to determine particle size. Some nanoparticle materials are not electron dense and thus cannot be stained; others melt and sinter when irradiated by the electron beam of the microscope and thus cannot be visualized by this method. Such nanoparticles can be visualized in TEM after freeze fracture or freeze substitution.42 This method is optimal because it also allows for the fracturing of the particles and consequently an observation of their interior. Unfortunately, the method is time-consuming and cannot be used for the routine determinations. Recently, new types of high-resolution microscopes such as the atomic-force microscope, the laser-force microscope, and the scanning-tunneling microscope were developed.43–46 These microscopes are especially useful for the investigation of nanoparticle surfaces.
Concavities of Crystalline Sintered Hydroxyapatite-Based Macroporous Bioreactors Initiate the Spontaneous Induction of Bone Formation
Ugo Ripamonti in The Geometric Induction of Bone Formation, 2020
Intramuscular implantation of hydroxyapatite/β-tricalcium phosphate (HA/βTCP) discs post-sinter 4/96 by ratios HA vs. βTCP (Figs. 5.14a,b) (Ripamonti et al. 2008) showed the induction of bone formation within the concavities of the substratum on day 90 in both 4/96 (Figs. 5.14c,d) and 19/81 post-sinter HA/βTCP (Fig. 5.14e). Substantial amounts of bone formed in concavities of post-sinter 4/96 and 19/81 HA/βTCP specimens on day 365 (Figs. 5.15c,d) (Ripamonti et al. 2008).
A systematic review of follow-up results of additively manufactured customized implants for the pelvic area
Published in Expert Review of Medical Devices, 2023
Jeffrey Zoltan, Diana Popescu, Seyed Hamid Reza Sanei
Table 3 provides a summary of the most common AM processes used in orthopedics along with their corresponding material system, energy source, and feedstock. Among the listed AM processes, Electron Beam Melting (EBM) predominates implant manufacturing [49]. In EBM, a thin layer of titanium powder is melted on the bed surface using a high energy electron beam generated by heating the tungsten filament. To avoid oxidization of titanium, a vacuum chamber is used to deprive oxygen during the process. Unlike sinter-based approaches (such as SLM – Selective Laser Melting), where the sintering process is required after the print to solidify the print into a denser component [50], the EBM components can be used immediately after the print, as the desired density has been achieved due to high energy melting of metal powder.
Physical barrier type abuse-deterrent formulations: monitoring sintering-induced microstructural changes in polyethylene oxide placebo tablets by near infrared spectroscopy (NIRS)
Published in Drug Development and Industrial Pharmacy, 2018
Heather J. Boyce, Ahmed Ibrahim, Stephen W. Hoag
As described above, many studies have used NIRS to assess tensile strength of tablets and a few accounts have examined sintering as one variable in the context of larger studies, but there have been no studies that monitored the actual sintering process using NIRS. Further, we propose use of the multiplicative scattering correction (MSC) algorithm as a new and fast way to calculate spectral slopes and intercept than what has been presented by previous authors [21–23]. Using this algorithm, it was our goal to determine if NIRS could be a suitable technique to evaluate the sintering process of a plastic material such as PEO in a pharmaceutical tablet [28]. Further, in the current study we sought to determine if NIRS can capture minute changes in the tablet microstructure that occur with increased sintering time using tensile strength as a response variable. Finally, we compare the use of partial least squares (PLS) to alternative algorithms such as spectral slope regression (SSR) models and spectral intercept regression (SIR) models to predict tensile strength values as a function of sinter time to confirm NIRS can be a suitable technique to monitor the sintering process [21].
The influence of input material properties on hot melt granules prepared using a counter-rotating batch mixer
Published in Pharmaceutical Development and Technology, 2023
Afstathios Pafiakis, Piero Armenante, Costas G. Gogos
Valsamis–Canedo experiments demonstrated that the energy dissipated in the mixing zone was large enough to sinter and partly melt the particulates. This random deformation mechanism in turn caused the particles to agglomerate. The fusing and the partial melting were attributed to the two melting mechanisms that involve polymer particulates PED and FED (Valsamis and Canedo 1994). Additionally, very little has been investigated on the roles of PED and FED in the initiation of rapid volume-wise melting in mixers with respect to input material properties. Gogos et al. investigated the agglomeration rate of powder blends containing three different amounts of fine polypropylene (PP) powder. It was concluded that the blend with the highest level of fines demonstrated the fastest onset of granule growth (Gogos et al. 1994).