Edge-losses occur during reflectance measurements of pigmented maxillofacial elastomer when light is scattered within a sample beyond that part of the surface exposed to the observation system of the optical device. A custom sample-holder is presented which redirects light that would not be measured during conventional reflectance measurement back into the sample. The amount of edge-loss occurring within thin layers of maxillofacial elastomer with tan pigment on black-and-white backings was found to depend on sample thickness, the backing, the beam size used during conventional reflectance measurement, and the optical term bS = (2KS + K2)1/2. Data analysis revealed a significant interaction among these four factors. Additionally, the edge-loss occurring during the tristimulus reflectance measurement of thick samples of maxillofacial elastomer with various concentrations of tan and black pigment was found to be linearly related to bS up to a limiting value, with no additional edge-loss occurring for bS values above this limiting value. Edge-loss is an important consideration during the matching of the optical characteristics of pigmented maxillofacial material to those of human skin.
Powder flowability is key to achieving high process stability and part quality by application of smooth and dense layers in selective laser sintering (SLS). This study sheds light on the rarely investigated effect of tribo-electric charge build-up during powder delivery in the SLS process. This is achieved by a novel approach to quantify electrostatic potentials during doctor blading. The presented model setup is used in combination with charge spectrometry and impedance spectroscopy to investigate the alterations in tribo-electric charging behavior for the most commonly used laser sintering material polyamide 12 in its virgin and aged, c.f. reused, states. We show that the electrostatic charge build-up is significantly enhanced for aged polymer powder material, likely contributing to altered performance in SLS processing.
For future integration into building facades or overhead glazing, the direct deposition of organic solar modules on glass substrates in sheet‐to‐sheet processes may be more cost efficient than postproduction lamination. Complying with the special requirements for the deposition of the layer stack on glass substrates, we report on all‐doctor‐bladed organic solar modules yielding power conversion efficiencies of 4.5 and 3.6 % on photoactive areas of 1 and 20 cm2, respectively. The bottom electrode is doctor bladed from a silver ink atop an adhesion enhancing primer. The top electrode is applied from silver nanowires, dispersed in poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), which thereby avoids any visible bus bars and reduces shading of the active layer. Importantly, all layers are deposited under ambient conditions by using only non‐chlorinated, eco‐compatible solvents.
Additive manufacturing, in particular powder bed-based fabrication processes hold promise to revolutionize biomedical engineering for the ability to provide customized, functional implants, for example as bone replacement materials. However, providing functional powder particles that unify material requirements for biodegradable and bioactive biomaterials and process requirements to enable successful powder bed fusion remains an unmet challenge. Here, a supraparticle-based approach to create biodegradable poly(lactic acid) and composite powders for the additive manufacturing of bone replacement materials is introduced. Colloidal binary Ca-SiO 2 glasses and hydroxyapatite are incorporated as bioactive functional additives to support the formation of bone-like calcium phosphate. The supraparticle powders are prepared by a scalable spraydrying process, which offers control of particle size, shape, and composition. All process-relevant powder characteristics are analyzed as a function of composition and structure, including flowability, thermal, and melt rheological properties. The optimized supraparticle powders are successfully used in the process of laser powder bed fusion of polymers to prepare macroscopic specimens via additive manufacturing. It is demonstrated that the material combination of the composites provides relevant functional properties, including biodegradation and bioactivity. The process provides a flexible and adjustable toolbox for the design of functional powders toward biomedical additive manufacturing.
Mucus consistency affects voice physiology and is connected to voice disorders. Nevertheless, the rheological characteristics of human laryngeal mucus from the vocal folds remain unknown. Knowledge about mucus viscoelasticity enables fabrication of artificial mucus with natural properties, more realistic ex-vivo experiments and promotes a better understanding and improved treatment of dysphonia with regard to mucus consistency. We studied human laryngeal mucus samples from the vocal folds with two complementary approaches: 19 samples were successfully applied to particle tracking microrheology (PTM) and five additional samples to oscillatory shear rheology (OSR). Mucus was collected by experienced laryngologists from patients together with demographic data. The analysis of the viscoelasticity revealed diversity among the investigated mucus samples according to their rigidity (absolute G’ and G”). Moreover some samples revealed throughout solid-like character (G’ > G”), whereas some underwent a change from solid-like to liquid-like (G’ < G”). This led to a subdivision into three groups. We assume that the reason for the differences is a variation in the hydration level of the mucus, which affects the mucin concentration and network formation factors of the mucin mesh. The demographic data could not be correlated to the differences, except for the smoking behavior. Mucus of predominant liquid-like character was associated with current smokers.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.