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As actuated devices become smaller and more complex, there is a need for smart materials and structures that directly function as complete mechanical units without an external power supply. The strategy uses light-powered, twisted, and coiled azobenzene-functionalized semicrystalline liquid crystal elastomer (AC-LCE) springs. This twisting and coiling, which has previously been used for only thermally, electrochemically, or absorption-powered muscles, maximizes uniaxial and radial actuation. The specially designed photochemical muscles can undergo about 60% tensile stroke and provide 15 kJ m -3 of work capacity in response to light, thus providing about three times and two times higher performance, respectively, than previous azobenzene actuators. Since this actuation is photochemical, driven by ultraviolet (UV) light and reversed by visible light, isothermal actuation can occur in a range of environmental conditions, including underwater. In addition, photoisomerization of the AC-LCEs enables unique latch-like actuation, eliminating the need for continuous energy application to maintain the stroke. Also, as the light-powered muscles processed to be either homochiral or heterochiral, the direction of actuation can be reversed. The presented approach highlights the novel capabilities of photochemical actuator materials that can be manipulated in untethered, isothermal, and wet environmental conditions, thus suggesting various potential applications, including underwater soft robotics., (© 2024 Wiley‐VCH GmbH.)

Success in making artificial muscles that are faster and more powerful and that provide larger strokes would expand their applications. Electrochemical carbon nanotube yarn muscles are of special interest because of their relatively high energy conversion efficiencies. However, they are bipolar, meaning that they do not monotonically expand or contract over the available potential range. This limits muscle stroke and work capacity. Here, we describe unipolar stroke carbon nanotube yarn muscles in which muscle stroke changes between extreme potentials are additive and muscle stroke substantially increases with increasing potential scan rate. The normal decrease in stroke with increasing scan rate is overwhelmed by a notable increase in effective ion size. Enhanced muscle strokes, contractile work-per-cycle, contractile power densities, and energy conversion efficiencies are obtained for unipolar muscles., (Copyright © 2021 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

Higher-efficiency, lower-cost refrigeration is needed for both large- and small-scale cooling. Refrigerators using entropy changes during cycles of stretching or hydrostatic compression of a solid are possible alternatives to the vapor-compression fridges found in homes. We show that high cooling results from twist changes for twisted, coiled, or supercoiled fibers, including those of natural rubber, nickel titanium, and polyethylene fishing line. Using opposite chiralities of twist and coiling produces supercoiled natural rubber fibers and coiled fishing line fibers that cool when stretched. A demonstrated twist-based device for cooling flowing water provides high cooling energy and device efficiency. Mechanical calculations describe the axial and spring-index dependencies of twist-enhanced cooling and its origin in a phase transformation for polyethylene fibers., (Copyright © 2019 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

Twisted-yarn-based artificial muscles can potentially be used in diverse applications, such as valves in microfluidic devices, smart textiles, air vehicles, and exoskeletons, because of their high torsional and tensile strokes, high work capacities, and long cycle life. Here, we demonstrate electrochemically powered, hierarchically twisted carbon nanotube yarn artificial muscles that have a contractile work capacity of 3.78 kJ/kg, which is 95 times the work capacity of mammalian skeletal muscles. This record work capacity and a tensile stroke of 15.1% were obtained by maximizing yarn capacitance by optimizing the degree of inserted twist in component yarns that are plied until fully coiled. These electrochemically driven artificial muscles can be operated in reverse as mechanical energy harvesters that need no externally applied bias. In aqueous sodium chloride electrolyte, a peak electrical output power of 0.65 W/kg of energy harvester was generated by 1 Hz sinusoidal elongation.

A novel geometry for electroluminescent devices, which does not require transparent electrodes for electrical input, is demonstrated, theoretically analyzed, and experimentally characterized. Instead of emitting light through a conventional electrode, light emission occurs through a polar liquid or solid and input electrical electrodes are coplanar, rather than stacked in a sandwich configuration. This new device concept is scalable and easily deployed for a range of modular alternating-current-powered electroluminescent light sources and light-emitting sensing devices. The polar-electrode-bridged electroluminescent displays can be used as remotely readable, spatially responsive sensors that emit light in response to the accumulation and distribution of materials on the device surface. Using this device structure, various types of alternating current devices are demonstrated. These include an umbrella that automatically lights up when it rains, a display that emits light from regions touched by human fingers (or painted upon using a mixture of oil and water), and a sensor that lights up differently in different areas to indicate the presence of water and its freezing. This study extends the dual-stack, coplanar-electrode device geometry to provide displays that emit light from a figure drawn on an electroluminescent panel using a graphite pencil., (© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Mechanical energy harvesters are needed for diverse applications, including self-powered wireless sensors, structural and human health monitoring systems, and the extraction of energy from ocean waves. We report carbon nanotube yarn harvesters that electrochemically convert tensile or torsional mechanical energy into electrical energy without requiring an external bias voltage. Stretching coiled yarns generated 250 watts per kilogram of peak electrical power when cycled up to 30 hertz, as well as up to 41.2 joules per kilogram of electrical energy per mechanical cycle, when normalized to harvester yarn weight. These energy harvesters were used in the ocean to harvest wave energy, combined with thermally driven artificial muscles to convert temperature fluctuations to electrical energy, sewn into textiles for use as self-powered respiration sensors, and used to power a light-emitting diode and to charge a storage capacitor., (Copyright © 2017 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

While artificial muscle yarns and fibers are potentially important for many applications, the combination of large strokes, high gravimetric work capacities, short cycle times, and high efficiencies are not realized for these fibers. This paper demonstrates here electrochemically powered carbon nanotube yarn muscles that provide tensile contraction as high as 16.5%, which is 12.7 times higher than previously obtained. These electrochemical muscles can deliver a contractile energy conversion efficiency of 5.4%, which is 4.1 times higher than reported for any organic-material-based artificial muscle. All-solid-state parallel muscles and braided muscles, which do not require a liquid electrolyte, provide tensile contractions of 11.6% and 5%, respectively. These artificial muscles might eventually be deployed for a host of applications, from robotics to perhaps even implantable medical devices., (© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Lightweight artificial muscle fibers that can match the large tensile stroke of natural muscles have been elusive. In particular, low stroke, limited cycle life, and inefficient energy conversion have combined with high cost and hysteretic performance to restrict practical use. In recent years, a new class of artificial muscles, based on highly twisted fibers, has emerged that can deliver more than 2,000 J/kg of specific work during muscle contraction, compared with just 40 J/kg for natural muscle. Thermally actuated muscles made from ordinary polymer fibers can deliver long-life, hysteresis-free tensile strokes of more than 30% and torsional actuation capable of spinning a paddle at speeds of more than 100,000 rpm. In this perspective, we explore the mechanisms and potential applications of present twisted fiber muscles and the future opportunities and challenges for developing twisted muscles having improved cycle rates, efficiencies, and functionality. We also demonstrate artificial muscle sewing threads and textiles and coiled structures that exhibit nearly unlimited actuation strokes. In addition to robotics and prosthetics, future applications include smart textiles that change breathability in response to temperature and moisture and window shutters that automatically open and close to conserve energy., Competing Interests: Provisional patent 62/371,744, “Twisted, plied, uniformly coiled, and non-uniformly coiled artificial muscles for textile applications,” was filed on August 6, 2016.

Superelastic conducting fibers with improved properties and functionalities are needed for diverse applications. Here we report the fabrication of highly stretchable (up to 1320%) sheath-core conducting fibers created by wrapping carbon nanotube sheets oriented in the fiber direction on stretched rubber fiber cores. The resulting structure exhibited distinct short- and long-period sheath buckling that occurred reversibly out of phase in the axial and belt directions, enabling a resistance change of less than 5% for a 1000% stretch. By including other rubber and carbon nanotube sheath layers, we demonstrated strain sensors generating an 860% capacitance change and electrically powered torsional muscles operating reversibly by a coupled tension-to-torsion actuation mechanism. Using theory, we quantitatively explain the complementary effects of an increase in muscle length and a large positive Poisson's ratio on torsional actuation and electronic properties., (Copyright © 2015, American Association for the Advancement of Science.)

Magnesium-diboride-coated carbon nanotube arrays are synthesized by templating carbon-nanotube aerogel sheets with boron and then converting the boron to MgB2. The resultant MgB2-CNT sheets are twisted into flexible, light-weight yarns that have a superconducting transition around 37.8 K and critical current and critical field comparable with those of existing MgB2 wires, but have about 20 times lower density than bulk MgB2., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The high cost of powerful, large-stroke, high-stress artificial muscles has combined with performance limitations such as low cycle life, hysteresis, and low efficiency to restrict applications. We demonstrated that inexpensive high-strength polymer fibers used for fishing line and sewing thread can be easily transformed by twist insertion to provide fast, scalable, nonhysteretic, long-life tensile and torsional muscles. Extreme twisting produces coiled muscles that can contract by 49%, lift loads over 100 times heavier than can human muscle of the same length and weight, and generate 5.3 kilowatts of mechanical work per kilogram of muscle weight, similar to that produced by a jet engine. Woven textiles that change porosity in response to temperature and actuating window shutters that could help conserve energy were also demonstrated. Large-stroke tensile actuation was theoretically and experimentally shown to result from torsional actuation.

Torsional artificial muscles generating fast, large-angle rotation have been recently demonstrated, which exploit the helical configuration of twist-spun carbon nanotube yarns. These wax-infiltrated, electrothermally powered artificial muscles are torsionally underdamped, thereby experiencing dynamic oscillations that complicate positional control. Here, using the strategy spiders deploy to eliminate uncontrolled spinning at the end of dragline silk, we have developed ultrafast hybrid carbon nanotube yarn muscles that generated a 9,800 r.p.m. rotation without noticeable oscillation. A high-loss viscoelastic material, comprising paraffin wax and polystyrene-poly(ethylene-butylene)-polystyrene copolymer, was used as yarn guest to give an overdamped dynamic response. Using more than 10-fold decrease in mechanical stabilization time, compared with previous nanotube yarn torsional muscles, dynamic mirror positioning that is both fast and accurate is demonstrated. Scalability to provide constant volumetric torsional work capacity is demonstrated over a 10-fold change in yarn cross-sectional area, which is important for upscaled applications.

Artificial muscles are of practical interest, but few types have been commercially exploited. Typical problems include slow response, low strain and force generation, short cycle life, use of electrolytes, and low energy efficiency. We have designed guest-filled, twist-spun carbon nanotube yarns as electrolyte-free muscles that provide fast, high-force, large-stroke torsional and tensile actuation. More than a million torsional and tensile actuation cycles are demonstrated, wherein a muscle spins a rotor at an average 11,500 revolutions/minute or delivers 3% tensile contraction at 1200 cycles/minute. Electrical, chemical, or photonic excitation of hybrid yarns changes guest dimensions and generates torsional rotation and contraction of the yarn host. Demonstrations include torsional motors, contractile muscles, and sensors that capture the energy of the sensing process to mechanically actuate.

Highly oriented graphene nanoribbons sheets and yarns are produced by chemical unzipping of self-standing multiwalled carbon nanotube (MWNT) sheets. The as-produced yarns - after being chemically and thermally reduced - exhibit a good mechanical, electrical, and electrochemical performance., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Multifunctional applications of textiles have been limited by the inability to spin important materials into yarns. Generically applicable methods are demonstrated for producing weavable yarns comprising up to 95 weight percent of otherwise unspinnable particulate or nanofiber powders that remain highly functional. Scrolled 50-nanometer-thick carbon nanotube sheets confine these powders in the galleries of irregular scroll sacks whose observed complex structures are related to twist-dependent extension of Archimedean spirals, Fermat spirals, or spiral pairs into scrolls. The strength and electronic connectivity of a small weight fraction of scrolled carbon nanotube sheet enables yarn weaving, sewing, knotting, braiding, and charge collection. This technology is used to make yarns of superconductors, lithium-ion battery materials, graphene ribbons, catalytic nanofibers for fuel cells, and titanium dioxide for photocatalysis.

Objective: This was to describe and analyse incidence and survival data on childhood leukaemias., Sample: Incident leukaemia cases aged 0-19 from the cancer registry holdings of the province of Saskatchewan for the 60-year period 1932-1991 are the subject of this descriptive report., Methods: Age-adjusted, age-specific, histologic-type specific, sex-specific, and cohort-specific incidence trends were reviewed. Univariate and multivariate survival analyses explored the effects of time period, age at diagnosis, gender, and histologic type., Results: Acute lymphocytic leukaemia (ALL) occurred more commonly in males and before the age of five; the 1982-1991 age-adjusted incidence is 3.1/100,000. Increasing incidence has been consistently noted, but has attenuated since 1971. The relative risk of developing ALL in the first 9 years of life, using children born from 1944 to 1948 as baseline, increased with each successive 5-year birth cohort until 1969-1973; since then the risk has been stable. Other histologic types were rare; over 60 years there were only 85 cases that could be grouped as acute non-lymphocytic leukaemias (ANLL); the 1982-1991 age-adjusted ANLL incidence is 0.6/100,000. A dramatic improvement in survival was seen over the last six decades, primarily for ALL. In ALL, children under five have better survival than older children and adolescents; the reverse is true for ANLL., Conclusions: ALL and ANLL are distinctive diseases clinically and the epidemiological findings are likewise distinctive. Our current ALL patterns are consonant with a number of other published reports. However, our small numbers of ANLL limit inferences.

The purpose of this study was to determine continuing education needs in the area of palliative care, as defined by family practice physicians. The methodology consisted of an anonymous questionnaire mailed in October, 1991, to all family practitioners in the city of Regina, Saskatchewan having admission privileges at any of the city's three hospitals. Replies were received from 31.1% of that population; the worst-case estimate is that about half of the city's palliative care caseload in 1991 was under the care of these respondents. In a priority-ranking format, physicians rated pain assessment and management as the patients' greatest need and their greatest continuing education need. Although emotional support and communication were highly ranked among other needs of patients, they were not highly ranked among education needs. Grand rounds was indicated as the educational venue of preference. Longer, more intensive educational formats were not selected. Communication of palliative status, including "Do not resuscitate" status, has reportedly become a routine practice. We have concluded that palliative care education should focus on the felt needs of family practice physicians for technical competence in pain assessment and management, using abbreviated formats. Cautious introduction of content areas and educational methods more likely to address patient needs is warranted. A one- or two-day workshop devoted to bereavement guidance might be a concrete focus for communication-oriented continuing education.