All-Solid-State Carbon Nanotube Torsional and Tensile Artificial Muscles

Abstract

We report electrochemically powered, all-solid-state torsional and tensile artificial yarn muscles using a spinnable carbon nanotube (CNT) sheet that provides attractive performance. Large torsional muscle stroke (53°/mm) with minor hysteresis loop was obtained for a low applied voltage (5 V) without the use of a relatively complex three-electrode electromechanical setup, liquid electrolyte, or packaging. Useful tensile muscle strokes were obtained (1.3% at 2.5 V and 0.52% at 1 V) when lifting loads that are ∼25 times heavier than can be lifted by the same diameter human skeletal muscle. Also, the tensile actuator maintained its contraction following charging and subsequent disconnection from the power supply because of its own supercapacitor property at the same time. Possible eventual applications for the individual tensile and torsional muscles are in micromechanical devices, such as for controlling valves and stirring liquids in microfluidic circuits, and in medical catheters.

Laser printing hierarchical structures with the aid of controlled capillary-driven self-assembly

“…These structures give rise to diverse functions ranging from mechanical strengthening (11) and directional adhesion (12,13) to superhydrophobicity (14) and structural colors (15), thus inspiring researchers to devote their efforts to mimic these multifunctional structures for decades. Many top-down fabrication approaches such as photolithography together with deep dry etching (16), replica molding (14, 17), multibeam laser interference lithography (18,19), and electron-beam lithography (20) have been used in combination with capillary force self-assembly to produce hierarchical structures.…”

High performance electrochemical and electrothermal artificial muscles from twist-spun carbon nanotube yarn

“…The precursor yarns used for electrochemical muscles [1,3] were similarly made as those described for thermally powered hybrid muscles [2]. These yarns were fabricated by drawing CNT sheets from a CNT forest (Figure 1a) and inserting twist into a sheet or sheet stack to make a twisted CNT yarn.…”

“…Lee et al [3] eliminated these problems by showing that laterally connected anode and cathode CNT yarns could be combined in one torsional yarn muscles (Figure 3), thereby enabling all-solid-state electrochemical muscles that provide giant torsional actuation. Identical twisted, non-coiled anode and cathode yarns were made by inserting twist into forest-drawn CNT sheets, and then infiltrating these yarns with a gel electrolyte (poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP), containing tetraethyl ammonium tetrafluoroborate (TEA.BF 4 ) with propylene carbonate (PC)).…”

“…These muscles are called hybrid CNT yarn muscles, since the thermally driven volume expansion of a guest within the twist-spun CNT yarn drives the reversible contraction (h) Illustration of a plied, coiled yarn muscle with attached weight for tensile actuation measurements, which had been over coated with the above electrolyte after plying [3].…”

“…Carbon nanotube (CNT) sheets drawn from spinnable CNT forests has been investigated for such applications as actuators [1][2][3], supercapacitors [4,5], solar cells [6], biofuel cells [7], and acoustic speaker [8]. There are many other potential application areas because of such properties as high electrical conductivity, high mechanical properties, optical transparency for single sheets, and high gravimetric surface area [4,9].…”