William B. Spillman

Effects of the chemical structure and the surface properties of polymeric biomaterials on their biocompatibility.

Polymeric biomaterials have extensively been used in medicinal applications. However, factors that determine their biocompatibility are still not very clear. This article reviews various effects of the chemical structure and the surface properties of polymeric biomaterials on their biocompatibility, including protein adsorption, cell adhesion, cytotoxicity, blood compatibility, and tissue compatibility. Understanding these aspects of biocompatibility is important to the improvement of the biocompatibility of existing polymers and the design of new biocompatible polymers.

Synthesis kinetics of CdSe quantum dots in trioctylphosphine oxide and in stearic acid

A diffusion-barrier model described the early evolution of size-dependent photoluminescence emission from CdSe quantum dots formed by organometallic synthesis. Emission peak widths, emission redshift rates, and nanocrystal growth rates all decreased to a minimum at a reaction completion time. Growth after the completion time by Ostwald ripening was marked by a doubling of the activation energy. The temperature dependence of both reaction completion rates and photoluminescence redshift rates followed Arrhenius behavior governed by activation energies that increased with solvent molecular weight, in this limited case. In stearic acid and in trioctylphosphine oxide, the typical activation energies were 0.6±0.1 and 0.92±0.26eV∕molecule, respectively.

Steady states of a microtubule assembly in a confined geometry.

We study the steady state of an assembly of microtubules in a confined volume, analogous to the situation inside a cell where the cell boundary forms a natural barrier to growth. We show that the dynamical equations for growing and shrinking microtubules predict the existence of two steady states, with either exponentially decaying or exponentially increasing distribution of microtubule lengths. We identify the regimes in parameter space corresponding to these steady states. In the latter case, the apparent catastrophe frequency near the boundary is found to be significantly larger than that in the interior. Both the exponential distribution of lengths and the increase in the catastrophe frequency near the cell margin is in excellent agreement with recent experimental observations.

Dielectric constant and breakdown field studies of electrostatic self-assembled materials

Electrical properties of electrostatic self-assembled (ESA) films were investigated using a conductive polymer and metal bar. These nanostructured polymeric films were fabricated on gold-coated glass slides using the ESA method. The thicknesses of the films were in the range 120?630?nm, and the films were obtained by depositing numbers of bilayers of negatively charged Poly s-119 (PS-119) or heparin and positively charged Poly(diallyldimethylammonium chloride) (PDDA). Measurement electrodes were fabricated on the ESA films using conductive silver grease and a brass bar. Capacitance measurements were conducted to determine the dielectric constant of the ESA films over various temperature and frequency ranges at 1?mV and 15% relative humidity, while electric field breakdown tests were performed at 1000?Hz, 15% relative humidity and varying temperatures and voltages. The test results showed that dielectric constant values were between 1.8 and 2.4 and breakdown field values were approximately 9?kV?mm?1. Based on the test results, it is concluded that this is a technique that might prove useful in estimating the capacitance, dielectric constant and breakdown field values of nanostructured ESA films.

Biocompatible thin film coatings fabricated using the electrostatic self-assembly process

Biomaterials are substances that are produced synthetically or biologically for use in the medical and the other fields. The use of biomaterials to interface with living systems, such as fluids, cells, and tissues of the body, has played an increasingly important role in medicine and pharmaceutics. In particular, the design of biocompatible synthetic surfaces to control the interaction between a living system and an implanted material remains the major theme for biomaterial applications in medicine. The novel and low-cost electrostatic self-assembly (ESA) technique provides an effective approach to incorporate various biomaterials on substrate surfaces, and gives greater opportunity to develop unique biocompatible materials with well-controlled interfaces between the living system and the implanted materia. This paper presents the design, synthesis, and characterization of multilayer thin films fabricated layer-by-layer by the ESA process using ceramics, polymers and functionalized fullerenes as candidate biomaterials.

Sensory phenomena and measurement instrumentation for smart structures and materials

This conference focuses on sensory mechanisms in smart material systems, methods for the instrumentation of integrated smart structural systems, and techniques for the characterization of smart or designed materials that are substantially different from methods used to characterize more conventional materials. In this paper, an overview of the purpose of the conference will be provided describing its place within smart structures research, the conference structure will be discussed, and some of the conference papers of note will be previewed.

Completely embedded optical fiber sensors

Due to their small size, light weight, geometric flexibility, and their possible uses for monitoring various different physical parameters, optical fiber sensor technology offers numerous opportunities and advantages for instrumenting structures and materials for their analysis and control. While optical fiber sensors have advantages over conventional electric sensors, connectorization of optical fiber sensors to the supporting laser, detector, and electronics has proven to be difficult. In this paper we demonstrate the possibility of having an optical fiber sensor system that can be completely embedded within composite materials. The fiber sensor as well as the supporting opto-electronic components required to launch and receive light into and from the fiber could be embedded in a panel, avoiding connector problems. Interaction with the electronics to obtain strain and vibration measurements from the fiber sensor was made via external antenna coils.

Cellular automata for the analysis of biomedical hyperspectral images

In this paper, we describe a technique whereby cellular automata are used to rapidly scan hyperspectral medical images and quantify the extent of conditions of medical interest. The cellular automata population uses the condition of interest as food and only grows in those areas of the image where the food is present. The size of the cellular automata population can be correlated with the fractional area of the image containing the condition of interest. The technique has the potential to significantly reduce the computational overhead required to analyze a hyperspectral image. A simple model of the technique will be described and the results of its operation on a specific hyperspectral image is presented.

Modeling the electro-static self-assembly process using stochastic cellular automata

The electro-static self-assembly (ESA) process has proved to be extremely successful in creating multilayer coatings with properties that can be tailored for particular applications. In this process, almost any surface with charged functional groups can be used as a substrate. Alternate dipping in solutions having ions of opposite charge builds up the layers through ionic bonding. One particular application of this process could be to form multi-functional biocompatible coatings on microelectromechanical systems devices intended for use in vivo. In this paper, we describe two different models of the process based on the cellular automata techniques used in the field of artificial life. The output of the models consists of three parameters as a function of layer: ionic coverage, film height and film roughness. The results of the models are compared to experimental data to determine which of them more accurately describes the ESA process.

Thermal cycling and the optical and electrical characterization of self-assembled multilayer Nile Blue A–gold thin films

Some laser applications produce high power densities that can be dangerous to equipment and operators. We have fabricated thin-film coatings by using molecular electrostatic self-assembly to create a spectrally selective absorbing coating that is able to withstand thermal fluctuations from -20 degrees C to 120 degrees C. We made the thin-film coatings by alternating deposition of an organic dye and gold colloidal nanoparticles onto glass substrates. Nile Blue A perchlorate, with a maximum absorbance slightly above 632 nm, was chosen as the organic dye. Strong coupling between the dye molecules and the gold nanoparticles provides a redshift that increases as the films thickness is increased. The incorporation of the gold colloidal nanoparticles also decreases the resistivity of the film. The resistivity of the film was measured with a four-point probe and found to be approximately 10 omega/cm for the two samples measured. Atomic-force microscopy was used to show that film thickness increased 2.4 nm per bilayer. The optical properties of the film were measured at the end of every 5 thermal cycles from -20 degrees C to 120 degrees C, and negligible degradation was observed after 30 cycles.