Electrostatic Force Microscopy: A Promising Diagnostic Tool to Measure Interphase Properties

There is currently no reliable method for studying interfacial regions within dielectric nanocomposites. The aim of this work was to develop experimental protocols and signal analysis involving Electrostatic Force Microscopy (EFM). Model samples made of spherical nanoparticles deposited on a metallic substrate and covered by two shells were designed and fabricated to simulate the presence of an interphase between a particle and a matrix. EFM performed either with DC or AC gradients detection method proved good sensitivity to certain sample configurations. A quantification of the dielectric permittivity of the intermediate layer was possible, thanks to correlation with finite element numerical simulations. Interfacial states between stacked layers, which can be attributed to film deposition processes, were also evidenced.

Characterization of Dielectric Nanocomposites with Electrostatic Force Microscopy

Nanocomposites physical properties unexplainable by general mixture laws are usually supposed to be related to interphases, highly present at the nanoscale. The intrinsic dielectric constant of the interphase and its volume need to be considered in the prediction of the effective permittivity of nanodielectrics, for example. The electrostatic force microscope (EFM) constitutes a promising technique to probe interphases locally. This work reports theoretical finite-elements simulations and experimental measurements to interpret EFM signals in front of nanocomposites with the aim of detecting and characterizing interphases. According to simulations, we designed and synthesized appropriate samples to verify experimentally the ability of EFM to characterize a nanoshell covering nanoparticles, for different shell thicknesses. This type of samples constitutes a simplified electrostatic model of a nanodielectric. Experiments were conducted using either DC or AC-EFM polarization, with force gradient detection method. A comparison between our numerical model and experimental results was performed in order to validate our predictions for general EFM-interphase interactions.

The role of alginates in regulation of food intake and glycemia: a gastroenterological perspective

Regulation of food intake through modulation of gastrointestinal responses to ingested foods is an ever-growing component of the therapeutic approaches targeting the obesity epidemic. Alginates, viscous and gel-forming soluble fibers isolated from the cell wall of brown seaweeds and some bacteria, are recently receiving considerable attention because of their potential role in satiation, satiety, and food intake regulation in the short term. Enhancement of gastric distension, delay of gastric emptying, and attenuation of postprandial glucose responses may constitute the basis of their physiological benefits. Offering physical, chemical, sensorial, and physiological advantages over other viscous and gel-forming fibers, alginates constitute promising functional food ingredients for the food industry. Therefore, the current review explores the role of alginates in food intake and glycemic regulation, their underlying modes of action and their potential in food applications.