Tuning the emission properties of a fluorescent polymer using a polymer microarray approach - identification of an optothermo responsive polymer

Fluorescent polymer microarrays were prepared using inkjet printing and screened. The fluorescence intensity was found to be tunable by temperature change when the dye was immobilized in identified thermo-responsive polymer beads.</p

Thickness control in a new flexible hybrid incremental sheet forming process

Incremental sheet forming is a cost-effective process for rapid manufacturing of sheet metal products. However, incremental sheet forming also has some limitations such as severe sheet thinning and long processing time. These limitations hamper the forming part quality and production efficiency, thus restricting the incremental sheet forming application in industrial practice. To overcome the problem of sheet thinning, a variety of processes, such as multi-step incremental sheet forming, have been proposed to improve the material flow and thickness distribution. In this work, a new process has been developed by introducing multi-point forming as preforming step before conducting incremental sheet forming processing. Employing an established hybrid sheet forming system and the corresponding thickness prediction model, the preform shape can be optimized by employing a two-step optimization approach to improve the sheet thickness distribution. In total, two case study examples, including a hemisphere part and an aerospace cowling part, are fabricated using the developed hybrid flexible process in this study. The experimental results show that the hybrid flexible forming process with the optimal preform design could achieve sheet parts with more uniform thickness distribution and reduced forming time

Design and Dynamic Equivalent Modeling of Double-Layer Hoop Deployable Antenna

This study proposes deployable units driven by elastic hinges and a double-layer hoop deployable antenna composed of these units. A rational modeling method based on the energy equivalence principle is presented to develop an equivalent model of the double-layer hoop antenna in accordance with the structural characteristics of the antenna. The equivalent beam models of the rods with elastic hinges are proposed. The relationship of geometrical and material parameters is established considering the strain energy and the kinetic energy of the periodic unit, which are the same as those of the equivalent beam in the same displacement field. The equivalent model of the antenna is obtained by assembling several equivalent beam models in the circumferential direction. The precision of the equivalent model of the antenna is acceptable as found by comparing the modal analysis results obtained through equivalent model calculation, finite element simulation, and modal test

Lightweight Self-Forming Super-Elastic Mechanical Metamaterials with Adaptive Stiffness

Scarcity of stiff, yet compliant materials is a major obstacle toward biological-like mechanical systems that perform precise manipulations while being resilient under excessive load. We introduce a macroscopic cellular structure comprising of two pre-stressed elastic “phases”, which displays a load-sensitive stiffness that drops by 30 times upon a “pseudo-ductile transformation” and accommodates a fully-recoverable compression of over 60%. This provides an exceptional 20 times more deform-ability beyond the linear-elastic regime, doubling the capability of previously reported super-elastic materials. In virtue of the pre-stressing process based on thermal-shrinkage, it simultaneously enables a heat-activated self-formation that transforms a flat laminate into the metamaterial with 50 times volumetric growth. The metamaterial is thereby inherently lightweight with a bulk density in the order of 0.01 g cm−3, which is one order of magnitude lower than existing super-elastic materials. Besides the highly-programmable geometrical and mechanical characteristics, this paper is the first to present a method that generates single-crystal or poly-crystal-like 3D lattices with anisotropic or isotropic super-elasticity. This pre-stress-induced adaptive stiffness with high deform-ability could be a step toward in-situ deployed ultra-lightweight mechanical systems with a diverse range of applications that benefit from being stiff and compliant

Catalytic synthesized carbon nanostructures from methane using nanocrystalline Ni

Carbon nanostructures synthesized with nanocrystalline Ni catalyst from decomposition of methane are investigated by means of transmission electron microscopy (TEM). Two kinds of carbon nanostructures, carbon fibers and bamboo-shaped carbon nanotubes, are observed. The preferential growth direction of graphene sheets depends on the reaction conditions. The bamboo-shaped carbon nanotubes can be obtained only if the reaction temperature is higher than 1000 K, and carbon fibers can be obtained at lower temperatures, The role and state of the catalyst particles are also discussed. (C) 2002 Elsevier Science Ltd. All rights reserved