scholarly journals Directional Stiffness Control Through Geometric Patterning and Localized Heating of Field’s Metal Lattice Embedded in Silicone

Actuators ◽  
2018 ◽  
Vol 7 (4) ◽  
pp. 80 ◽  
Author(s):  
Emily Allen ◽  
John Swensen
Keyword(s):  
Melting Point ◽  
Silicone Rubber ◽  
Lattice Structure ◽  
Tissue Stiffness ◽  
Physical Test ◽  
Metal Lattice ◽  
Rigid Frame ◽  
Serial Chain ◽  
Localized Heating ◽  
Stiffness Control

This research explores a new realm of soft robotic materials where the stiffness magnitude, directionality, and spatial resolution may be precisely controlled. These materials mimic biological systems where localized muscle contractions and adjustment of tissue stiffness enables meticulous, intelligent movement. Here we propose the use of a low-melting-point (LMP) metal lattice structure as a rigid frame using localized heating to allow compliance about selectable axes along the lattice. The resulting shape of the lattice is modeled using product of exponentials kinematics to describe the serial chain of tunably compliant axes; this model is found to match the behavior of the physical test piece consisting of a Field’s metal (FM) lattice encased in silicone rubber. This concept could enable highly maneuverable robotic structures with significantly improved dexterity.

scholarly journals A theoretical formula for the solubility of hydrogen in metals

1937 ◽  
Vol 160 (900) ◽  
pp. 37-47 ◽  
Keyword(s):  
Lattice Structure ◽  
Specific Interaction ◽  
Pure Metal ◽  
Normal Metal ◽  
Theoretical Formula ◽  
Theoretical Treatment ◽  
Solubility Curve ◽  
Hydrogen Atoms ◽  
Metal Lattice ◽  
The Difference

1— In certain metals such as Cu, hydrogen appears to be dissolved in the metal in the form of free protons, which do not affect the normal metal lattice, even when present at very considerable concentrations. In other metals such as Ti, definite metal hydrides are formed which have a different lattice structure from the pure metal. The metal Pd is intermediate since the hydrogen affects the lattice constant. It is the properties of the former group of metals which are first to be discussed here, since the fact that the normal metal lattice is (practically) unaffected seems to justify a very simple theoretical treatment of the solubility, and it is of some interest to examine how the theory compares with the facts. We shall find that we can bring the facts and the theory into satisfactory order together. The various types of solubility curve are shown in fig. 1. 2— From evidence such as the well-known p 1/2 law for the rate of diffusion of hydrogen through metals we may certainly assume that the hydrogen in the metal is atomic. For the present we shall neglect the difference between atoms of hydrogen and protons plus electrons, and merely assume that the atoms are present as such in the metal, without specific interaction with particular metallic atoms; the metal merely provides a region in which hydrogen atoms can exist and move in a definite field of potential energy. Specific contributions by the electrons of the hydrogen atoms will be considered later, when the hydrogen atoms in the metal will be considered as protons plus electrons.

Design and Experimentation of a Tunably-Compliant Robotic Finger Using Low Melting Point Metals

2016 ◽  
Author(s):  
Heon Joo ◽  
John P. Swensen
Keyword(s):  
Melting Point ◽  
Thermal Contact ◽  
Metal Casting ◽  
Skeletal Structure ◽  
Global Changes ◽  
Intermediate Step ◽  
Selective Heating ◽  
Localized Heating ◽  
Skeletal Geometry ◽  
Multiple Step

In this paper, we describe the fabrication and testing of a tunably-compliant tendon-driven finger implemented through the geometric design of a skeleton made of the low-melting point Field’s metal encased in a silicone rubber. The initial prototype consists of a skeleton comprised of two rods of the metal, with heating elements in thermal contact with the metal at various points along its length, embedded in an elastomer. The inputs to the systems are both the force exerted on the tendon to bend the finger and the heat introduced to liquefy the metal locally or globally along the length of the finger. Selective localized heating allows multiple joints to be created along the length of the finger. Fabrication was accomplished via a multiple step process of elastomer casting and liquid metal casting. Heating elements such as power resistors or Ni-Cr wire with electric connections were added as an intermediate step before the final elastomer casting. The addition of a tradition tendon actuation was inserted after all casting steps had been completed. While preliminary, this combination of selective heating and engineered geometry of the low-melting point skeletal structure will allow for further investigation into the skeletal geometry and its effects on local and global changes in device stiffness.

The coalescence of Cu nanoparticles with different interfacial lattice structures: A molecular dynamics study

2020 ◽  
pp. 2150149
Author(s):  
Jinchen Cao ◽  
Leilei Li ◽  
Cheng Zhang
Keyword(s):  
Molecular Dynamics ◽  
Melting Point ◽  
3D Printing ◽  
Dynamic Simulation ◽  
Sintering Temperature ◽  
Lattice Structure ◽  
Lattice Structures ◽  
Cu Nanoparticles ◽  
Heating Rates ◽  
The World

With the popularization of 3D printing technology, micro/nanoparticles sintering technology has drawn lots of attentions all over the world. Here, molecular dynamic simulation is employed to discuss the effects of different interfacial lattice structures, different diameter of nanoparticles, and different heating rates on the coalescence of metallic Cu nanoparticles. The results showed that the diameter of nanoparticles determine the melting point of the system. Besides, the interfacial lattice structure, diameter of nanoparticles, and heating rate have an influence on the initial sintering temperature. This is because the melting point is the inherent property of material which relies on the mass of substance. However, the initial sintering temperature is sensitive to many factors, including the temperature, interfacial, and intermolecular interactions.

Determination of Effective Crosslink Density in Silicone Rubber

1965 ◽  
Vol 38 (4) ◽  
pp. 924-939
Author(s):  
Robert D. Seeley ◽  
George W. Dyckes
Keyword(s):  
Silicone Rubber ◽  
Crosslink Density ◽  
Theoretical Calculations ◽  
Empirical Relationships ◽  
Physical Test ◽  
Swelling Agent ◽  
Rubber Compounds ◽  
Resultant Data ◽  
Volume Swelling

Abstract As a result of the investigations reported here, a simple and precise method was evised to measure the compression-deflection of solvent-swollen silicone rubber. The method was found to be reliable, and the resultant data were used to calculate effective crosslink densities of solid and cellular silicone rubber compounds. Empirical equations were derived relating compression and deflection to effective crosslinking of solid and cellular silicone rubber swollen in toluene. The weak swelling action of MEK precludes the derivation of empirical relationships between compression, deflection, and effective cross-linking of the rubber. The investigation further showed that toluene is a better and more useful swelling agent than methyl ethyl ketone (MEK). The volume swelling ratios for toluene and MEK were determined. Toluene was found to be about 1.4 times more effective as a swelling agent than MEK. Limited laboratory physical test data show a reasonable correlation to νe/Vr data. (More testing will be required to establish definite relationships.) This investigation also showed that the method employed here for crosslinking determinations is suitable for cellular rubber, since the data obtained from toluene-swollen specimens agrees quite well with theoretical calculations. Finally, the Flory-Huggins interaction parameters for toluene and MEK were determined.

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