Self-Repairing Membranes for Inflatable Structures Inspired by a Rapid Wound Sealing Process of Climbing Plants

A new self-repairing membrane for inflatable light weight structures such as rubber boats or Tensairity constructions is presented. Inspired by rapid self-sealing processes in plants, a thin soft cellular polyurethane foam coating is applied on the inside of a fabric substrate, which closes the fissure if the membrane is punctured with a spike. Experimental tests are carried out with a purpose built setup by measuring the air mass flow through a leak in a damaged membrane sample. It is shown that the weight per unit area of the self-repairing foam as well as the curing of the two component PU-foam under an overpressure influence the repair efficiency. Curing the foam under overpressure affects the relative density as well as the microstructure of the foam coatings. Maximal median repair efficiencies of 0.999 have been obtained with 0.16 g.cm 2 foam cured at 1 bar overpressure. These results suggest that the bio-inspired technique has the potential to extend the functional integrity of injured inflatable structures dramatically.

Effect of Pre-Harvest Application of Gibberellic Acid on Fruit Quality and Shelf Life of Mandarin (Citrus reticulata Blanco)

Mandarin (Citrus reticulata Blanco) is a promising fruit crop gaining popularity for its human nutrition and economic importance in Nepal. The qualitative losses during pre-harvest stage hinder the productivity and subsequently shorten the on-tree storability. An experiment was conducted to assess the effect of gibberellic acid on quality and shelf life of the mandarin fruit. GA3 at 10, 20, and 30 ppm as against of control were evaluated. Observations on fruit weight (g), fruit firmness (kg/cm2), rind colour (1 - 5 index), juice recovery (%), TSS/acid ratio, PLW (%), decay loss (%), and ascorbic acid (mg/100 ml) were recorded at three harvesting dates i.e. 20 Nov, 5 Dec, and 20 Dec and storage condition. It has been revealed that the fruits treated with GA3 at 20 ppm retained higher fruit weight (128.6 g), more firmness (3.54 kg/cm2), better juice recovery (57.75%), and greater TSS/acid ratio (21.24) at the end of study (20 December). The PLW was found less with GA3 at 30 ppm in both ambient (5.17%) and cellar (6.69%) condition as against untreated fruits (9.52% and 11.76%). Similarly, the decay loss was minimum in the fruits treated with GA3 at 30 ppm both with ambient (1.02%) and cellar condition (8.21%) as against control with ambient (5.54%) and cellar (21.58%).

Molecular movements of trehalose inside a single network enabling a rapidly-recoverable tough hydrogel

It remains a challenge to achieve rapidly recoverable hydrogels by molecular hydrogen-bonding interaction because of its slow inter-action kinetics.This work for the first time reports a trehalose(Tre)-based molecular movement mechanism inside a single network of polyacrylamide(PAM)that accelerates the kinetics of hydrogenbonding interaction,and thereby endows the hydrogel with high toughness and rapid shape and mechanical recoverability.The resultant PAM@Tre hydrogel is capable of full shape recovery after 10,000 loading/unloading cycles at a strain of 500%.Even after being stretched at a strain of 2500%,it can recover to its original shape within 10 seconds.Moreover,the molecular movement of trehalose also endows the PAM@Tre hydrogel with fracture energy and toughness as high as~9000 J m^(-2) and~1600 kJ m^(-3),respec-tively,leading to strong resistance to both static and dynamic piercing.The PAM@Tre hydrogel is thus believed to have enormous potentials in protection devices,bionic skin,soft actuator,and stretchable electronics.