Nanoscience and Nanotechnology

INTRODUCTION Self-assembled monolayers (SAMs) are monomolecular layers that are spontaneously formed on immersing a solid substrate into a solution containing active surfactant molecules. The best studied examples are silanes, which are used to modify, for example, silica and mica surfaces, and alkylthiols, which have an affinity for coinage metals.[1] Organic SAMs can be used to […]

Adhesion Between Surfaces Coated with Self-Assembled Monolayers: Effect of Humidity Part 2 (Nanotechnology)

ALKYLSILANE SAMS ON SILICA The effect of humidity on the adhesion of alkylsilane SAMs deposited on Si/SiO2 surfaces has been more thoroughly investigated compared with alkylthiols on gold in part because of the importance of antiadhesive coatings in silicon-based MEMS devices. An important difference between SAMs formed by alkylthiols and organosilanes is the possibility for […]

Adhesion of a Cell on a Substrate Part 1 (Nanotechnology)

INTRODUCTION Life would not exist if the molecules involved did not interact in a very dynamical way. An equilibrium situation must not be reached and evolution has to be continual. This implies that life originates from interactions and bonds that are weak and have a short lifetime (1 msec to several days) because of thermal […]

Adhesion of a Cell on a Substrate Part 2 (Nanotechnology)

EXPERIMENTAL VERIFICATION OF THE MODEL To test this model, a suitable technique is based on vesicle adhesion measurement by micromanipulation.1-6-1 It consists in holding a slightly deflated 10- to 30-p.m vesicle in a micropipette with a controlled aspiration. At the start of the experiment, the shape of the vesicle is a segment of sphere outside […]

Adsorption of Polymers and Proteins on Heterogeneous Surfaces Part 1 (Nanotechnology)

INTRODUCTION In this review, we focus on the role of surface heterogeneity in polymer adsorption and discuss novel experiments that clarify the impact of topographical and chemical heterogeneity on adsorption of flexible polymers and globular proteins. The comparison of the experimental results with existing theoretical predictions provides valuable insights into the adsorption process and guides […]

Adsorption of Polymers and Proteins on Heterogeneous Surfaces Part 2(Nanotechnology)

IMPACT OF CHEMICAL HETEROGENEITY Design of surfaces using SAMs provides a hitherto unexplored approach to experimentally understand the effects of chemical heterogeneity of surfaces on polymer adsorption.[27,28] It is well known that millimeter- or micrometer-sized patterns in self-assembled monolayers can be created using techniques such as UV photooxida-tion, microcontact printing, and micromachining.[29] However, these patterns […]

Aerosol Nanoparticles: Theory of Coagulation Part 1 (Nanotechnology)

INTRODUCTION Many important physical properties of natural or man-made aerosol particles such as light scattering, electrostatic charges, and toxicity, as well as their behavior involving physical processes such as diffusion, condensation, and thermophoresis, depend strongly on their size distribution. An important aerosol behavior mechanism affecting the size distribution of aerosol particles is coagulation. Aerosol particles […]

Aerosol Nanoparticles: Theory of Coagulation Part 2 (Nanotechnology)

SOLUTIONS TO THE COAGULATION EQUATION Methods of solving a coagulation equation were summarized by Williams and Loyalka.[17] These methods range from the discrete (computationally intensive) and sectional models in which Eq. 5 is transformed into a number of differential equations, to the less accurate mo-nodisperse models. Approximate solutions can be found using the method of […]

Aerospace Applications for Epoxy Layered-Silicate Nanocomposites Part 1 (Nanotechnology)

INTRODUCTION Research on polymer nanocomposites based on layered silicates has exploded over the last decade,[1-5] ever since the pioneering work of the organoclay-nylon nanocompo-site by Toyota.[6] The dispersion of the silicate nanolayer with its high aspect ratio, large surface area, and high stiffness within a polymer matrix results in significant improvement of the properties of […]

Aerospace Applications for Epoxy Layered-Silicate Nanocomposites Part 2(Nanotechnology)

PROCESSING AND MORPHOLOGY DEVELOPMENT DSC studies show that the onset temperatures of polymerization are much lower for the Epon 862/W with organoclays than those for pure Epon 862/W 65-100°C vs. 122°C). The catalytic effect is likely because of the acidity from the ammonium (RNH3+) group of the pendent group from the organomontmorillonite.[15,18,19,39,40] The mechanism for […]