published in\u00a0Science Robotics<\/a>. The work is led by Media Lab PhD candidate Ozgun Kilic Afsar; Vito Cacucciolo, a professor at\u00a0the Politecnico di Bari; and four co-authors.<\/p>\nThe new system brings together two technologies, Afsar explains. One is a fluidically driven artificial muscle known as a thin McKibben actuator, and the other is a miniaturized solid-state pump based on electrohydrodynamics (EHD), which can generate pressure inside a sealed fluid compartment without moving parts or an external fluid supply.<\/p>\n
Until now, most fluid-driven soft actuators have relied on external \u201cheavy, bulky, oftentimes noisy hydraulic infrastructure,\u201d Afsar says, \u201cwhich makes them difficult to integrate into systems where mobility or compact, lightweight design is important.\u201d This has created a fundamental bottleneck in the practical use of fluidic actuators in real-world applications.<\/p>\n
The key to breaking through that bottleneck was the use of integrated pumps based on electrohydrodynamic principles. These millimeter-scale, electrically driven pumps generate pressure and flow by injecting charge into a dielectric fluid, creating ions that drag the fluid along with them. Weighing just a few grams each and not much thicker than a toothpick, they can be fabricated continuously and scaled easily. \u201cWe integrated these fiber pumps into a closed fluidic circuit with the thin McKibben actuators,\u201d Afsar says, noting that this was not a simple task given the different dynamics of the two components.<\/p>\n
A key design strategy was to pair these fibers in what are known as antagonistic configurations. Cacucciolo explains that this is where \u201cone muscle contracts while another elongates,\u201d as when you bend your arm and your biceps contract while your triceps stretch. In their system, a millimeter-scale fiber pump sits between two similarly scaled McKibben actuators, driving fluid into one actuator to contract it while simultaneously relaxing the other.<\/p>\n
\u201cThis is very much reminiscent of how biological muscles are configured and organized,\u201d Afsar says. \u201cWe didn\u2019t choose this configuration simply for the sake of biomimicry, but because we needed a way to store the fluid within the muscle design.\u201d The need for an external reservoir open to the atmosphere has been one of the main factors limiting the practical use of EHD pumps in robotic systems outside the lab. By pairing two McKibben fibers in line, with a fiber pump between them to form a closed circuit, the team eliminated that need entirely.<\/p>\n
Another key finding was that the muscle fibers needed to be pre-pressurized, rather than simply filled. \u201cThere is a minimum internal system pressure that the system can tolerate,\u201d Afsar says, \u201cbelow which the pump can degrade or temporarily stop working.\u201d This happens because of cavitation, in which vapor bubbles form when the pressure at the pump inlet drops below the vapor pressure of the liquid, eventually leading to dielectric breakdown.<\/p>\n
To prevent cavitation, they applied a \u201cbias\u201d pressure from the outset so that the pressure at the fiber pump inlet never falls below the liquid\u2019s vapor pressure. The magnitude of this bias pressure can be adjusted depending on the application. \u201cTo achieve the maximum contraction the muscle can generate, we found there is a specific bias pressure range that is optimal,\u201d she says. \u201cIf you want to configure the system for faster response, you might increase that bias pressure, though with some reduction in maximum contraction.\u201d<\/p>\n
Cacucciolo adds that most of today\u2019s robotic limbs and hands are built around electric servo motors, whose configuration differs fundamentally from that of natural muscles. Servo motors generate rotational motion on a shaft that must be converted into linear movement, whereas muscle fibers naturally contract and extend linearly, as do these electrofluidic fibers.\u00a0<\/p>\n
\u201cMost robotic arms and humanoid robots are designed around the servo motors that drive them,\u201d he says. \u201cThat creates integration constraints, because servo motors are hard to package densely and tend to concentrate mass near the joints they drive.\u00a0By contrast, artificial muscles in fiber form can be packed tightly inside a robot or exoskeleton and distributed throughout the structure, rather than concentrated near a joint.\u201d<\/p>\n
These electrofluidic muscles may be especially useful for wearable applications, such as exoskeletons that help a person lift heavier loads or assistive devices that restore or augment dexterity. But the underlying principles could also apply more broadly. \u201cOur findings extend to fluid-driven robotic systems in general,\u201d Cacucciolo says. \u201cWherever fluidic actuators are used, or where engineers want to replace external pumps with internal ones, these design principles could apply across a wide range of fluid-driven robotic systems.\u201d<\/p>\n
This work \u201cpresents a major advancement in fiber-format soft actuation,\u201d which \u201caddresses several long-standing hurdles in the field, particularly regarding portability and power density,\u201d says Herbert Shea, a professor in the Soft Transducers Laboratory at Ecole Polytechnique Federale de Lausanne in Switzerland, who was not associated with this research. \u201cThe lack of moving parts in the pump makes these muscles silent, a major advantage for prosthetic devices and assistive clothing,\u201d he says.<\/p>\n
Shea adds that \u201cthis high-quality and rigorous work bridges the gap between fundamental fluid dynamics and practical robotic applications. The authors provide a complete system-level solution \u2014 characterizing the individual components, developing a predictive physical model, and validating it through a range of demonstrators.\u201d<\/p>\n
In addition to Afsar and Cacucciolo, the team also included Gabriele Pupillo and Gennaro Vitucci at Politecnico di Bari and Wedyan Babatain and Professor Hiroshi Ishii at the MIT Media Lab. The work was supported by the European Research Council and the Media Lab\u2019s multi-sponsored consortium.<\/p>\n","protected":false},"excerpt":{"rendered":"Muscles are remarkably effective systems for generating controlled force, and engineers developing hardware for robots or prosthetics have…\n","protected":false},"author":2,"featured_media":595968,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[6],"tags":[290902,64,63,71825,290903,290904,290905,134513,290909,290906,290908,96740,105,290907],"class_list":{"0":"post-595967","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-technology","8":"tag-artificial-muscle-fibers","9":"tag-au","10":"tag-australia","11":"tag-biomimicry","12":"tag-electrofluidic","13":"tag-electrohydrodynamics","14":"tag-mckibben-actuator","15":"tag-mit-media-lab","16":"tag-ozgun-kilic-afsar","17":"tag-robot-muscles","18":"tag-smart-fibers","19":"tag-soft-robotics","20":"tag-technology","21":"tag-wearable-medical-devices"},"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/posts\/595967","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/comments?post=595967"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/posts\/595967\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/media\/595968"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/media?parent=595967"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/categories?post=595967"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/tags?post=595967"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}