Biomedical subjects

Shoufeng Yang

Publications and source records attributed to Shoufeng Yang.

5 recordsLinked to original sources

PubMed2006

Fine ceramic lattices prepared by extrusion freeforming.

Fine ceramic lattices with spatial resolution <100 microm and having precise dimensions and intricate hierarchical structure are fabricated by extrusion freeforming, a rapid prototyping technique, which allows overall shape and structure to be controlled by computer. The procedure can be used for any fine ceramic powder and can therefore find applications as diverse as microwave and terahertz metamaterials (artificial crystals), hard tissue scaffolds, microfluidic devices, and metal matrix composite preforms. The examples presented here are calcium phosphate lattices with three structure levels: submicron pores, which enhance cell-surface interactions, pores of tens of microns to encourage bone ingrowth, and corridors (hundreds of microns) for vascularization. With controlled pore structures on these scales, the lattices are expected to provide customized biological, mechanical, and geometrical requirements.

Biocompatible Materials↗

PubMed2004

Structural chemistry of new lithium bis(oxalato)borate solvates.

Recently lithium bis(oxalato)borate, LiB(C2O4)2, has been proposed as an alternative lithium salt for the electrolyte in rechargeable batteries that do not contain explosive perchlorate, reactive fluoride or toxic arsenic. This lithium salt crystallizes in the form of solvates from such solvents as water, acetonitrile, acetone, dimethoxyethane, 1,3-dioxolane and ethylene carbonate. Their crystal structures were determined in order to explore the crystal chemistry of this lithium salt. It was found that most of the solvents consist of a lithium bis(oxalato)borate dimer in which the ligand acts as both a chelating and a bridging agent. Lithium has octahedral coordination that typically includes one or, less commonly, two solvent molecules. An exception to this rule is the ethylene carbonate solvate where the lithium is tetrahedrally surrounded exclusively by the solvent and bis(oxalato)borate plays the role of counter-ion only. The ethylene carbonate solvates were also studied for LiPF6 and LiAsF6 salts and they have similar structures to the bis(oxalato)borate tetrahedral complexes.

Journal Article↗

PubMed2003

Structures of potassium, sodium and lithium bis(oxalato)borate salts from powder diffraction data.

The crystal structures of the alkali-metal bis(oxalato)borate salts A[B(C2O4)2] (A = K, Na, Li) have been determined ab initio using powder diffraction data obtained from a laboratory diffractometer. The K compound crystallizes in the orthorhombic space group Cmcm and its structure has been solved by direct methods applied to the integrated intensities from full pattern decomposition. The Na compound is isostructural with the K salt, while the crystal structure of the highly hydroscopic Li compound differs from the other two. It has an orthorhombic lattice, space group Pnma, and its structure was solved by the global optimization method using a parallel tempering approach. In the K and Na structures the metal ions and complex borate ions form chains with m2m symmetry. Metal-oxygen bonding between the chains links them into a layer and then a framework with square tunnels. The coordination number of both K and Na is eight. The Li compound also contains chains that have .m. symmetry and are bound together into a three-dimensional framework. The coordination polyhedron of the Li atom is a square pyramid with Li lying in its base. This square pyramidal coordination leads to its high reactivity with moisture to give Li[B(C2O4)2]H2O with lithium in six coordination.

Journal Article↗

PubMed2002

The design of scaffolds for use in tissue engineering. Part II. Rapid prototyping techniques.

Tissue engineering (TE) is an important emerging area in biomedical engineering for creating biological alternatives for harvested tissues, implants, and prostheses. In TE, a highly porous artificial extracellular matrix or scaffold is required to accommodate mammalian cells and guide their growth and tissue regeneration in three-dimension (3D). However, existing 3D scaffolds for TE proved less than ideal for actual applications because they lack mechanical strength, interconnected channels, and controlled porosity or pores distribution. In this paper, the authors review the application and advancement of rapid prototyping (RP) techniques in the design and creation of synthetic scaffolds for use in TE. We also review the advantages and benefits, and limitations and shortcomings of current RP techniques as well as the future direction of RP development in TE scaffold fabrication.

Animals↗

PubMedDate not supplied

Device for preparing combinatorial libraries in powder metallurgy.

This paper describes a powder-metering, -mixing, and -dispensing mechanism that can be used as a method for producing large numbers of samples for metallurgical evaluation or electrical or mechanical testing from multicomponent metal and cermet powder systems. It is designed to make use of the same commercial powders that are used in powder metallurgy and, therefore, to produce samples that are faithful to the microstructure of finished products. The particle assemblies produced by the device could be consolidated by die pressing, isostatic pressing, laser sintering, or direct melting. The powder metering valve provides both on/off and flow rate control of dry powders in open capillaries using acoustic vibration. The valve is simple and involves no relative movement, avoiding seizure with fine powders. An orchestra of such valves can be arranged on a building platform to prepare multicomponent combinatorial libraries. As with many combinatorial devices, identification and evaluation of sources of mixing error as a function of sample size is mandatory. Such an analysis is presented.

Journal Article↗