Fast Sheath-driven Electrothermal Artificial Muscles with High Power Densities

Electrothermal carbon nanotube (CNT) yarn muscles can provide large strokes during heating-cooling cycles. However, the slow cooling rate of thermal muscles limit their applications, since large diameter prior-art thermal muscles cannot be rapidly cycled. We here report an ultrafast thermally powered sheath-driven yarn muscle that uses a hybrid CNT sheath and an inexpensive polymer core. Our coiled muscle contracts 14.3% at 1 Hz and 7.3% at 8 Hz in air when powered by a square-wave electrical voltage input. The 70-mm-diameter actuated muscle cools in air to 16℃ from 150℃ within 0.5 s, compared with 6 s for a 65-mm-diameter sheath-run muscle that uses an electrothermally heated CNT core and 9 s for a 78-mm-diameter muscle that uses the sheath material for the entire muscle. An average power density of 12 kW/kg was obtained for a sheath-driven muscle, which is 42 times that for human skeletal muscle. This high performance results since the heating that drives fast actuation cycles is largely restricted to the muscle sheath, and this sheath is in direct contact with ambient temperature air.

PENGARUH PANJANG STACK SELUBUNG KABEL TERHADAP PERUBAHAN SUHU PADA SISTEM PENDINGIN TERMOAKUSTIK

Research on environmentally friendly thermo-acoustic coolants uses a heat exchanger from the cable sheath material. The resonator tube used in the thermoelectric cooler is a 5.25 cm diameter PVC (polyvinyl chloride) tube with a length of 87 cm. Variations in stack lengths of 4cm, 5cm, 6cm, 7cm, and 8cm were performed to obtain results on thermoelectric coolers. Results are available on the use of stack length 4 cm high temperature 21.6 oC from the initial temperature), the stack length 5 cm high temperature 21.1 oC from the initial temperature (room temperature), the stack length of 6 cm resulted in a maximum temperature drop of 22.6 oC from the initial temperature (room temperature), the stack length of 7 cm resulted in a maximum temperature drop of 22.0 oC from the initial temperature (room temperature), while the stack length of 8 cm resulted in a decrease in temperature maximum of 23.3 oC from the initial temperature (room temperature). Keywords: Thermoacoustic, stack, temperature changes.

A model for sheath formation coupled to motility inLeptothrix ochracea

Optical and atomic force microscopy (AFM) of naturally occurringLeptothrix ochraceawas used to study the fine structure of sheaths and cells. Morphology of young sheaths suggests the scaffold chains have strong self-adhesion. Evidence from un-encapsulated cells indicates fresh scaffold production through cell walls. Simple diffusion arguments are used to explain the morphology of the sheath structure. We propose a novel cell motility model based on previously published video data, our AFM images of naked cells, and simple flow calculations. The model indicates that motility results from differential shear forces resulting from extrusion of sheath material that passively pushes a filament of connected cells forward as the surrounding sheath material hardens behind the cell train.

A Comparative Strength Analysis of Denim Fabrics Made from Core-Spun Yarns Containing Textured Microfilaments

Denim fabric is one of the most popular casual wear fabrics worldwide. The performance characteristics of denim fabrics have been improved by using functional fibers and elastane to make them comfortable to wear. Elastane fibers with high elasticity are used extensively in denim fabric production. Elastane fibers are generally used as the core part of the core-spun yarns as weft yarns. Besides elastane fibers; polyester and polyester derivatives are commonly used. This study examines the effects of filament fineness and yarn count on denim fabric performance. Textured polyester filaments with medium, fine and micro linear densities were used as the core part of the core-spun yarn and cotton fiber was used as sheath material. Yarn samples manufactured with the same production parameters at different yarn count were used as weft yarns of denim fabrics. Denim fabrics were produced with the same fabric cover factor to eliminate yarn count difference effects. Tensile, static tearing and dynamic tearing properties of denim fabrics were determined. To evaluate the effects of core part, 100 % cotton denim fabric was manufactured and tested. Statistical analysis was performed to analyze the significance of filament fineness and yarn count ratio. Results showed that there was a significant effect of filament fineness on tensile, static tearing and dynamic tearing properties of denim fabrics. In addition, it was found that yarn count had no significance effect on static tearing properties of denim fabrics.