The area of artificial muscle is a highly interdisciplinary field of research that has evolved rapidly in the last 30 years. Recent advances in nanomaterial fabrication and characterization, ...specifically carbon nanotubes and nanowires, have had major contributions in the development of artificial muscles. However, what can artificial muscles really do for humans? This question is considered here by first examining nature's solutions to this design problem and then discussing the structure, actuation mechanism, applications, and limitations of recently developed artificial muscles, including highly oriented semicrystalline polymer fibers; nanocomposite actuators; twisted nanofiber yarns; thermally activated shape‐memory alloys; ionic‐polymer/metal composites; dielectric‐elastomer actuators; conducting polymers; stimuli‐responsive gels; piezoelectric, electrostrictive, magnetostrictive, and photostrictive actuators; photoexcited actuators; electrostatic actuators; and pneumatic actuators.
Artificial muscles are muscle‐like actuators that contract, bend, or twist in response to an external stimulus. Recent advances in nanotechnology and microsystems have enabled a new class of materials suitable for artificial‐muscle application. Different types of artificial muscle, including the recently invented actuators, are introduced and their applications and limitations are discussed.
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2.
Resources for finance lawyers Hunter, Ian
Legal information management,
06/2023, Volume:
23, Issue:
2
Journal Article
Peer reviewed
Financing work is an important source of revenue for many law firms, so it's no surprise that the finance practice group is often one of the largest in a City firm. But what is finance and what do ...finance lawyers do? Ian Hunter, Content & Research Manager (EMEA) at Shearman & Sterling (London) LLP, gives LIM the benefit of his wide experience in the sector.
Multidirectional artificial muscles are made from highly oriented nylon filaments. Thanks to the low thermal conductivity of nylon and its anisotropic thermal expansion, bending occurs when a nylon ...beam is differentially heated. This heat can be generated via a Joule heating mechanism or high power laser pulses.
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Torsional artificial muscles made of multiwalled carbon nanotube/niobium nanowire yarns have shown remarkable torsional speed and gravimetric torque. The muscle structure consists of a twisted yarn ...with half of its length infiltrated with a stimuli-responsive guest material such as paraffin wax. The volumetric expansion of the guest material creates the torsional actuation in the yarn. In the present work, we show that this type of actuation is not unique to wax-infiltrated carbon multiwalled nanotube (MWCNT) or niobium nanowire yarns and that twisted yarn of NiTi alloy fibers also produces fast torsional actuation. By gold-plating half the length of a NiTi twisted yarn and Joule heating it, we achieved a fully reversible torsional actuation of up to 16°/mm with peak torsional speed of 10 500 rpm and gravimetric torque of 8 N·m/kg. These results favorably compare to those of MWCNTs and niobium nanowire yarns.
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Planar micro‐supercapacitors are attractive for system on chip technologies and surface mount devices due to their large areal capacitance and energy/power density compared to the traditional ...oxide‐based capacitors. In the present work, a novel material, niobium nanowires, in form of vertically aligned electrodes for application in high performance planar micro‐supercapacitors is introduced. Specific capacitance of up to 1 kF m−2 (100 mF cm−2) with peak energy and power density of 2 kJ m−2 (6.2 MJ m−3 or 1.7 mWh cm−3) and 150 kW m−2 (480 MW m−3 or 480 W cm−3), respectively, is achieved. This remarkable power density, originating from the extremely low equivalent series resistance value of 0.27 Ω (2.49 µΩ m2 or 24.9 mΩ cm2) and large specific capacitance, is among the highest for planar micro‐supercapacitors electrodes made of nanomaterials.
Fast‐charging micro‐supercapacitors are made from vertically aligned niobium nanowire arrays. Thanks to the high electrical conductivity of the nanowires, the micro‐supercapacitor exhibits a very small characteristic relaxation time constant of 8.4 ms. With 1 m sulfuric acid, cycling rates of up to 300 V s−1 are achieved, while with 1‐ethyl‐3‐methylimidazolium tetrafluoroborate, an operating voltage of up to 4 V is obtained.
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Pneumatic artificial muscles have been widely used in industry because of their simple and relatively high-performance design. The emerging field of soft robotics has also been using pneumatic ...actuation mechanisms since its formation. However, these actuators/soft robots often require bulky peripheral components to operate. Here, we report a simple mechanism and design for actuating pneumatic artificial muscles and soft robotic grippers without the use of compressors, valves, or pressurized gas tanks. The actuation mechanism involves a magnetically induced liquid-to-gas phase transition of a liquid that assists the formation of pressure inside the artificial muscle. The volumetric expansion in the liquid-to-gas phase transition develops sufficient pressure inside the muscle for mechanical operations. We integrated this actuation mechanism into a McKibben-type artificial muscle and soft robotic arms. The untethered McKibben artificial muscle generated actuation strains of up to 20% (in 10 seconds) with associated work density of 40 kilojoules/meter
, which favorably compares with the peak strain and peak energy density of skeletal muscle. The untethered soft robotic arms demonstrated lifting objects with an input energy supply from only two Li-ion batteries.
In this article Ian Hunter considers his experiences, learning points and recommendations on running an international law firm research service from home for 6 months, after being sent home at one ...hour's notice. In the article he considers working from home, including the psychological benefits of having a ‘journey’ to work, providing a research service and a library service, managing a team and the use of communications technology.
Optical spectroscopy has a broad scientific basis in chemistry, physics, and material science, with diverse applications in medicine, pharmaceuticals, agriculture, and environmental monitoring. ...Fourier transform infrared (FTIR) spectrometers and tunable laser spectrometers (TLS) are key devices for measuring optical spectra. Superior performance in terms of sensitivity, selectivity, accuracy, and resolution is required for applications in gas sensing. This review deals with gas measurement based on either direct optical absorption spectroscopy or photoacoustic spectroscopy. Both approaches are applicable to FTIR spectroscopy or TLS. In photoacoustic spectroscopy, cantilever‐based photoacoustic spectroscopy is focused due its high performance. A literature survey is conducted revealing the recent technological advances. Theoretical fundamental detection limits are derived for TLS and FTIR, considering both direct absorption and photoacoustic spectroscopies. A theoretical comparison reveals which technology performs better. The minimum normalized absorption coefficient and normalized noise equivalent absorption coefficient appear as key parameters for this comparison. For TLS‐based systems, direct absorption spectroscopy is found to be the best for lower laser power and longer path length. For FTIR‐based systems, direct absorption is found to be the best for low temperature sources, higher spectrometer throughput, faster mirror velocity, and longer gas cells.
A literature survey on gas sensing and analysis covers both direct optical absorption spectroscopy and photoacoustic spectroscopy, both approaches being applicable to either Fourier transform infrared spectroscopy or tunable laser spectroscopy. The theoretical detection limits serve as guidelines. The paper reviews recent technological advances and prospects toward ubiquitous spectral sensing.
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Abstract Needle-free drug delivery by jet injection is achieved by ejecting a liquid drug through a narrow orifice at high pressure, thereby creating a fine high-speed fluid jet that can readily ...penetrate skin and tissue. Until very recently, all jet injectors utilized force- and pressure-generating principles that progress injection in an uncontrolled manner with limited ability to regulate delivery volume and injection depth. In order to address these shortcomings, we have developed a controllable jet injection device, based on a custom high-stroke linear Lorentz-force motor that is feed-back controlled during the time-course of an injection. Using this device, we are able to monitor and modulate continuously the speed of the drug jet, and regulate precisely the volume of drug delivered during the injection process. We demonstrate our ability to control injection depth (up to 16 mm) and repeatably and precisely inject volumes of up to 250 μL into transparent gels and post-mortem animal tissue.
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