ABSTRACT
Many emerging applications in microscale engineering rely on the fabrication of 3D architectures in inorganic materials. Small-scale additive manufacturing (AM) aspires to provide flexible and facile access to these geometries. Yet, the synthesis of device-grade inorganic materials is still a key challenge toward the implementation of AM in microfabrication. Here, a comprehensive overview of the microstructural and mechanical properties of metals fabricated by most state-of-the-art AM methods that offer a spatial resolution ≤10 µm is presented. Standardized sets of samples are studied by cross-sectional electron microscopy, nanoindentation, and microcompression. It is shown that current microscale AM techniques synthesize metals with a wide range of microstructures and elastic and plastic properties, including materials of dense and crystalline microstructure with excellent mechanical properties that compare well to those of thin-film nanocrystalline materials. The large variation in materials' performance can be related to the individual microstructure, which in turn is coupled to the various physico-chemical principles exploited by the different printing methods. The study provides practical guidelines for users of small-scale additive methods and establishes a baseline for the future optimization of the properties of printed metallic objects-a significant step toward the potential establishment of AM techniques in microfabrication.
ABSTRACT
Recently, well-ordered biological materials have been exploited to pattern inorganic nanoparticles into linear arrays that are of particular interest for nanoelectronic applications. In this work, a de novo designed E. coli-expressed polypeptide (previously shown to form highly rectilinear, ß-sheet-containing structures) operates as a template for divalent metal cations. EDX and TEM analysis verify the attachment of platinum ions to the histidine-rich fibril surface, which was designed specifically to facilitate attachment of chemical moieties. Following chemical reduction, TEM further confirms the formation of localized zero-valent metal aggregates with sub-nanometer interparticle spacing.
Subject(s)
Biocompatible Materials/chemical synthesis , Nanotechnology/methods , Peptides/chemistry , Platinum/chemistry , Amino Acid Sequence , Biocompatible Materials/analysis , Cations, Divalent/chemistry , Escherichia coli , Histidine/chemistry , Microscopy, Electron, Transmission , Molecular Sequence Data , Peptides/genetics , Protein Engineering , Protein Structure, Secondary , Recombinant Proteins/chemistry , Recombinant Proteins/genetics , Spectrometry, X-Ray EmissionABSTRACT
A de novo, genetically engineered 687 residue polypeptide expressed in E. coli has been found to form highly rectilinear, beta-sheet containing fibrillar structures. Tapping-mode atomic force microscopy, deep-UV Raman spectroscopy, and transmission electron microscopy definitively established the tendency of the fibrils to predominantly display an apparently planar bilayer or ribbon assemblage. The ordered self-assembly of designed, extremely repetitive, high molecular weight peptides is a harbinger of the utility of similar materials in nanoscience and engineering applications.
Subject(s)
Lipid Bilayers/chemistry , Lipid Bilayers/chemical synthesis , Peptides/chemistry , Peptides/chemical synthesis , Protein Engineering , Base Sequence , DNA/chemistry , DNA/genetics , Lipid Bilayers/isolation & purification , Microscopy, Atomic Force , Microscopy, Electron, Transmission , Molecular Sequence Data , Molecular Weight , Particle Size , Peptides/isolation & purification , Protein Conformation , Protein Structure, Secondary , Sensitivity and Specificity , Spectrum Analysis, RamanABSTRACT
OBJECTIVES: When a physician believes that the troubles of caring for a patient outweigh the rewards, he or she can move--"turf", the unwanted patient from his or her own to another physician's territory. Physicians receiving such patients can feel burdened by, and resentful about, caring for those who are "turfed" to them by other physicians, yet little is known about the effects such "turf battles" have on patient care. This study aims to discover if "turfed" patients (TPs) experience their hospitalizations differently from patients whose admissions are perceived more favorably by their physicians. DESIGN: Semi-structured, in-depth interviews. POPULATION: Twenty Six English-speaking patients on a medical service in a tertiary care university hospital. OUTCOMES: Hospitalization experiences based on qualitative thematic analysis of interview audiotapes and transcripts. RESULTS: The experience of patients perceived as "turfs" differed from patients deemed more appropriately admitted in two areas: mode of admission and tone of interview themes. TPs were admitted via the emergency department or intra-hospital transfer; unlike the "appropriate" patients (APs), none came from outside hospitals. Although patients in both groups voiced many similar themes, nearly all TP interview themes were unfavorable. AP interviewees, by comparison expressed both favorable and unfavorable themes. TPs were direct and explicit about their anger and frustration, while APs mixed humor with complaints. CONCLUSIONS: "Turfed" patients may have different care experiences from those of patients deemed appropriate for a medical service. Inter-specialty barriers to collegiality and relationship-centered care shape physicians' perceptions of patient appropriateness and desirability and merit further large-scale exploration.
