Recoverable Liquid Metal Paste with Reversible Rheological Characteristic for Electronics Printing.

Gallium-based liquid metals are applied in the fabrication of soft electronics because of their conductivity and flexibility. However, the large surface tension and weak adhesion of liquid metals limit the available printing substrates. Recent researches indicate that amalgamating metal particles can turn liquid metal from fluid into a paste which has superb electrical conductivity, plasticity, and strong adhesion to substrates. In this work, a recoverable liquid metal paste was made by mixing eutectic Ga-In alloy and nonmetallic SiO2 (quartz) particles (Ga-In-SiO2 paste, called GIS). GIS has excellent conductivity and printable properties similar to those of previously reported liquid metal pastes. Furthermore, the bonding between Ga-In alloy and quartz particles is reversible. In acidic or alkaline solution, Ga-In alloy can be separated from quartz particles and agglomerated to bulk by stirring. Moreover, the study of the mechanism of adhesion behavior suggests that extruding fresh liquid metal droplets to form more oxide and shearing friction are the critical factors for adhesion. This work proposed a new liquid metal paste with a reversible rheological property and promoted the understanding of the working principle of liquid metal paste.

Physicochemical and rheological properties of pomelo albedo pectin and its interaction with konjac glucomannan.

Pomelo albedo was extracted with water to obtain the high methoxyl pectin, labeled as PAP. The physicochemical and rheological properties of PAP were determined. The effects of PAP addition on rheological property and thermal stability of konjac glucomannan (KGM) were evaluated. Results indicated that PAP was composed of arabinose, glucose and galacturonic acid with a relative mass percentage of 7.2%: 9.5%: 83.3%, and exhibited an average molecular weight of 56.6 kDa. The degree of esterification of PAP was 65.5%, showing PAP was a kind of high methoxyl pectin. Apparent viscosity of PAP was concentration-dependently increased, while it was slightly enhanced with salt (NaCl or CaCl2) addition. Moreover, the addition of PAP declined the apparent viscosity, elastic property and thermal stability of KGM. It can be concluded that interaction was occurred between KGM and PAP. Meanwhile, the interaction mechanism between KGM and PAP has been preliminarily proposed. The present study can provide some references for the application of PAP and support the combination usage of this pectin and KGM in food and other industries.

Physicochemical properties of a water soluble extracellular homopolysaccharide from Lactobacillus reuteri SK24.003.

A water soluble exopolysaccharide was obtained from Lactobacillus reuteri SK24.003 and its rheological and structural properties were investigated. The polysaccharide yield reached around 40.8g/L for 48h of fermentation. The purified exopolysaccharide was an α-d-glucan with the molecular weight of 2.50×10(7)g/mol. Thermal analysis showed the exopolysaccharide broke down above 200°C, the weight dramatically lost (around 53.0%) from 230 to 340°C and the melting point was 147.7°C with the enthalpy value of 78.4J/g. The glucan solution (3.0-9.0%, v/w) has an opalescent, milky-white color and the concentration affected the depth of color. The viscosity increased rapidly with concentration in the range of 3.0-20% (w/v) with relatively high viscosity as well as poor solubility at a concentration higher than 20% (w/v). The solution also exhibited the non-Newtonian pseudoplastic behavior with increasing shear rate from 0.01 to 100l/s. This glucan had a high viscosity in solution and this could make it suitable for usage as gum substitute in some processing food.