Mechanically programmed soft actuators with conforming sleeves

A mechanically programmed actuator includes at least one soft actuator body configured to bend, linearly extend, contract, twist, or combinations thereof when actuated without constraint; an activation mechanism (e.g., a fluid pump) configured to actuate the soft actuator body; and at least one sleeve wrapped around part of the soft actuator body and configured to constrain the soft actuator body inside the sleeve when actuated and to cause the soft actuator body to deform where not covered by the sleeve.

BACKGROUND

Soft actuators offer several desirable features not found in rigid mechanical systems including the ability to embed complex motions into a monolithic structure, and inherent compliance due to the elastomeric materials and pressurized fluids. Computer-aided drafting (CAD) programs and three-dimensional (3D) printers allow relatively fast iteration of mold designs for actuator fabrication (on the order of days); these approaches, however, may not allow for “on-the-fly” modification of a soft actuator's output motions, connection interfaces, and surface properties. This capacity is advantageous where immediate customization is needed, such as on the production floor for robotic manipulation or rehabilitation, where patient needs vary.

SUMMARY

Mechanically programmed soft actuators and methods for their fabrication and use are described herein. Various embodiments of the apparatus and methods may include some or all of the elements, features and steps described below.

A mechanically programmed soft actuator includes at least one soft actuator body where a least a portion of it is configured to bend, linearly extend, contract, twist or combinations thereof when actuated without constraint; an activation mechanism (e.g., a fluid pump) configured to actuate the soft actuator body; and at least one conforming sleeve wrapped around part of the soft actuator body and configured to constrain the soft actuator body inside the sleeve when actuated and to cause the soft actuator body to bend where it is not covered by the sleeve.

In a method for mechanical actuation, fluid (e.g., air or liquid) is pumped into a chamber defined by the soft actuator body, causing the soft actuator body to bend where the soft actuator body is not covered by the sleeve, while the sleeve constrains bending of the soft actuator body where the sleeve covers the soft actuator body.

Embodiments of these actuators can provide for safe human-robot interaction, where soft tissues (e.g., skin) can interact with soft and compliant robotic actuators to increase comfort and to reduce the risk of injury to the user. These soft actuators are suitable for a variety of uses including use as robotic actuators to assist human movement, use as a conformable gripper for manipulating objects and use in toys (e.g., as an interface for video games).

In the accompanying drawings, like reference characters refer to the same or similar parts throughout the different views; and apostrophes are used to differentiate multiple instances of the same or similar items sharing the same reference numeral. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating particular principles, discussed below.

DETAILED DESCRIPTION

The foregoing and other features and advantages of various aspects of the invention(s) will be apparent from the following, more-particular description of various concepts and specific embodiments within the broader bounds of the invention(s). Various aspects of the subject matter introduced above and discussed in greater detail below may be implemented in any of numerous ways, as the subject matter is not limited to any particular manner of implementation. Examples of specific implementations and applications are provided primarily for illustrative purposes.

Unless otherwise defined, used or characterized herein, terms that are used herein (including technical and scientific terms) are to be interpreted as having a meaning that is consistent with their accepted meaning in the context of the relevant art and are not to be interpreted in an idealized or overly formal sense unless expressly so defined herein. For example, if a particular composition is referenced, the composition may be substantially, though not perfectly pure, as practical and imperfect realities may apply; e.g., the potential presence of at least trace impurities (e.g., at less than 1 or 2%) can be understood as being within the scope of the description; likewise, if a particular shape is referenced, the shape is intended to include imperfect variations from ideal shapes, e.g., due to manufacturing tolerances. Percentages or concentrations expressed herein can represent either by weight or by volume.

Although the terms, first, second, third, etc., may be used herein to describe various elements, these elements are not to be limited by these terms. These terms are simply used to distinguish one element from another. Thus, a first element, discussed below, could be termed a second element without departing from the teachings of the exemplary embodiments.

Spatially relative terms, such as “above,” “below,” “left,” “right,” “in front,” “behind,” and the like, may be used herein for ease of description to describe the relationship of one element to another element, as illustrated in the figures. It will be understood that the spatially relative terms, as well as the illustrated configurations, are intended to encompass different orientations of the apparatus in use or operation in addition to the orientations described herein and depicted in the figures. For example, if the apparatus in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the exemplary term, “above,” may encompass both an orientation of above and below. The apparatus may be otherwise oriented (e.g., rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

Further still, in this disclosure, when an element is referred to as being “on,” “connected to,” “coupled to,” “in contact with,” etc., another element, it may be directly on, connected to, coupled to, or in contact with the other element or intervening elements may be present unless otherwise specified.

The terminology used herein is for the purpose of describing particular embodiments and is not intended to be limiting of exemplary embodiments. As used herein, singular forms, such as “a” and “an,” are intended to include the plural forms as well, unless the context indicates otherwise. Additionally, the terms, “includes,” “including,” “comprises” and “comprising,” specify the presence of the stated elements or steps but do not preclude the presence or addition of one or more other elements or steps.

The methods and actuator designs disclosed, herein, can put the power of soft actuator customization into the user's hands and can eliminate the need to mold a new soft actuator to fit a particular application. As described herein, sleeves16can be used to mechanically program soft actuators12, which allows rapid modification (e.g., on the order of minutes) of a soft actuator's motion and capabilities. As an example,FIGS. 1 and 2show the motion of a curling soft actuator12when actuated by an activation mechanism18(e.g., as a pump fills the soft actuator body14with fluid). One means for generating the curling motion is to adhere a strain-limiting layer54that resists elastic or plastic deformation along its length (relative to unrestrained portions of the soft actuator body14), thereby causing curling of the actuator12, as shown inFIG. 5, when under stress (e.g., an increase in internal pressure). This motion can be adjusted by applying sleeves16, such as shrink tubing, to the soft actuator body14and leaving a full or partial opening where bending motion is desired, as shown inFIGS. 3 and 4. Wrapping the soft actuator body14with such a sleeve16can convert the soft curling actuator body14to a more-acutely bending actuator (or can convert a linear actuator into a bending actuator, as discussed below and as shown inFIGS. 72-80) and can produce a distinctly different motion (e.g., joint-like bending). The use of sleeves16also enables new opportunities to add a variety of features and capabilities to the soft actuator body14, such as interfacing with sensors26, electronics, mechanical tools, and other soft actuators and inclusion of printed circuit boards28mounted thereon (see,FIGS. 18-24, 35-39 and 49). As shown inFIGS. 21 and 22, the sleeve can also include mounts32(in the form of threaded posts in this embodiment) for mounting other objects33to the sleeve16or for mounting the sleeve16to other structures. As shown inFIGS. 23 and 24, the actuator12can be mounted to rigid links34, which are joined at a pivot36to form an actuating pivoting structure.

Soft actuator bodies14of this disclosure include walls that define a chamber20that can be formed of, e.g., hyper-elastic silicone, thermo plastic elastomer, thermo plastic urethane, rubber, elastic polyurethane, or polyethylene. Accordingly, the soft actuator body14can be designed to expand its dimensions, e.g., to 200% of its original dimensions before failure, while the sleeve16in which the soft actuator body14is contained can be formed of a flexible, rigid, and/or elastomeric material (e.g., in the form of a non-expanding fabric with, for example, no more than 1/10th the elasticity of the soft actuator body14), such that the sleeve16constrains the soft actuator body14and such that the soft actuator body14presses against the sleeve16when the soft actuator body14is expanded (e.g., by an increase in internal pressure).

The combination of the soft actuator body14and constraining sleeve16can include any or all of the following features. First, the sleeves16can alter the motion of a soft actuator body14. A single sleeve16can be used to move the bending position anywhere along the length of the soft actuator body14by limiting any part of the soft actuator body14that is enclosed in the sleeve16from deforming, as shown inFIG. 6, and by promoting deformation at an aperture22(in the form, e.g. of a slit or a cut-out, as shown inFIG. 45) in the sleeve16. In additional embodiments, two sleeves16can be positioned and spaced apart to move the bending position and to alter the actuator's radius of curvature to create joint-like bending, as shown inFIGS. 3, 4, and 7. Additionally, the sleeves16can be thermoformed; or secured with a securing mechanism24, such as pinch clamps24′, laces24″ (e.g., with cable ties), rubber bands24′″, zip ties24″″, inter-locking hook-and-loop structures24″″′ (e.g., VELCRO adhesive), or sewn thread; or rolled on thermally welded on or glued to the soft actuator body14, as shown inFIGS. 8-14. In particular embodiments where the soft actuator12is used for medical applications, both the soft actuator body14and the sleeve16can be formed of or coated with a biocompatible material, such as silicone or parylene polymer. .In additional embodiments, sleeves16can be cut to different lengths to change the location and bending radius of “joints” created in the soft actuator12. Additionally, the sleeves16can be designed to be removable from the soft actuator body14to free the soft actuator body14for re-use [e.g., the sleeves16can be cut off, slid off, untied, pulled apart (particularly when hook and loop structures are used), removed via the application of heat, etc.]

In still more embodiments, sleeves16can be used to create multiple joints with different radii of curvature around multiple axes on a single soft actuator body14, as shown inFIGS. 15-17 and 46-48. The soft actuator body14does not necessarily have to contain a strain-limiting layer. Alternatively, the soft actuator body can be a linear extending soft actuator or any elastomeric bladder; and the uncut band of sleeve material behind the aperture22can perform the function of the strain-limiting layer54, as shown inFIGS. 73-80.

The sleeves16can also act as a medium to interface with a whole suite of applications including the following: acting as an anchor point for electronics (e.g., an inertial measurement unit and mechanical contact switches); acting as an anchor point for soft sensors26and30(e.g., may be secured via interlocking hook and loop structures, sewn together, glued together, etc.); acting as an interface to connect rigid devices to a soft actuator body14(e.g., coupling to the actuator12, via a mount32, a scoop, lever, spring, or any mechanism that needs to be actuated); integrating or embedding magnets38(e.g., to facilitate alignment during grasping, attaching tools39, or to use for rapid collection of ferrous metal objects40), as shown inFIGS. 25-27; connecting multiple soft actuator bodies14in parallel, as shown inFIGS. 30 and 31, or in series (e.g., serving as X-, T-, and L-joints or end-to-end joints, as shown inFIGS. 28, 29, and 32-34), wherein the sleeves16can be used to create 3D structures; providing any of a variety of textures for gripping, twisting, sliding, or rolling objects (e.g., via brushes44, a sticky surface, a bumpy surface46, or via attachment mechanisms, such as hooks and/or loops48, as shown inFIGS. 35-37); and routing tubing or wiring52through perimeter channels50to minimize snagging and tangling of the tubes and wires52, as shown inFIGS. 38 and 39.

InFIGS. 83-85, a sleeve16that includes gripping features49for interfacing with objects is shown; the sleeve16can also extend further across the soft actuator body14and include apertures22or other features for bending or other forms of actuation, as shown in other embodiments.

In other embodiments, as shown inFIGS. 40 and 41, connected ring-shaped sleeve16sections that are narrow in width and spaced appropriately along a strain-limiting layer54can still achieve many of the interface applications, described above, without significantly changing the curling motion of the actuator12.

The sleeves16can be formed of a single piece of material with cut-outs or slits22at different longitudinal and radial positions along and about the sleeve16, as shown inFIGS. 46-48, 76 and 77, defining multiple bending positions along multiple axes and that can be used to join a plurality of soft actuator bodies14, as shown inFIGS. 32-34(e.g., with multiple interconnected sleeve ends).

Shown inFIGS. 42-44, at one end of the sleeve16is a fixture58attached to the soft actuator body14and including the pneumatic connection60which provides for fluid communication between a pump18and the chamber20defined by the walls of the soft actuator body14. The range of motions of a 28A durometer sleeved soft bending actuator12at sleeve spacings of (a) 0 mm, (b) 15 mm, and (c) 30 mm are respectively shown for comparison inFIGS. 42-44. The shadow images56show the actuators12bending at different pressures.

The sleeves16can be anchored to the surface of the soft actuator body14through mechanical features on the surface of the soft actuator body14(e.g., bumps, bellows, Kevlar ribs, other geometric locking features, etc.); and the sleeves16can be formed with fiber reinforcement. The sleeves16can also have integrated electrical wiring62(as shown inFIG. 49), a circuit board28, heating elements, cooling elements, temperature sensors, routing channels50, capacitive sensors, force sensors26, strain sensors30and so forth.

In particular applications, the sleeves16can connect a soft actuator body14to a human (or other animal) body part63, such as a finger, as shown inFIG. 50(wherein the actuator12may be, e.g., 3-15 cm in length with a thickness of, e.g., 0.5 to 2 cm), or to any other jointed body part. In other embodiments, the sleeves16can connect soft actuator bodies14to clothing.

In additional embodiments, as shown inFIGS. 52, 53, 55, 55, and 58-60, soft actuators12can be assembled into a manipulator body64, where sleeves16can be cut to different lengths to match (e.g., within 5%) the shape/dimensions of an object66to be grasped. For comparison, manipulators with sleeve-less curling soft actuator bodies14are shown inFIGS. 51, 54, and 57, where the curled soft actuators12can be seen to not conform closely to the surfaces of the object66to be manipulated. In the embodiments ofFIGS. 54-56, an additional downward force is applied to the object66via a hook67extending from the object66. Use of the proposed sleeve16enables improved shape matching to angular objects66and improved holding strength. In these embodiments, sleeve length can be tuned/adjusted (e.g., by rolling, sliding, screwing/unscrewing, etc.), as shown inFIGS. 61-69, to match the lengths of sides of the object66to be manipulated; and the sleeves16can be constructed from or combined with materials with rigid, flexible, and elastomeric properties. For example, a sleeve16can join two rigid components54to make a compliant joint, as shown inFIGS. 70 and 71.

FIG. 70provides a cross-sectional comparison of a fiber-reinforced actuator12with and without a fiber-reinforced laminate, where (a) shows an illustrated cross section and actual side view of an unpressurized fiber-reinforced actuator12; (b) shows expansion of the actuator walls due to fluid pressurization (note the outward bowing of the flat face15); (c) demonstrates placement of the fiber-reinforced laminate on a fiber-reinforced actuator12; and (d) shows an illustrated cross-sectional view of the actuator12when a sleeve16is added. The combination of the sleeve16and fiber-reinforced laminate stiffens the flat face15and eliminates or reduces visual indications of bowing.

FIG. 86presents an alternative to the design of embodiment (c) inFIG. 70, where instead of integrating rigid elements54with the sleeve16to stiffen portions of the actuator, vacuum jamming pouches80are integrated into the sleeve16. In this embodiment, the fluid line60connects to a vacuum source. Contained in the vacuum jamming pouches80are loose particles or laminate layers initially at atmospheric pressure. However, when these sections are exposed to a vacuum, the pouch walls close in on the contents, restricting their movement, and causing a phase transition (i.e., jamming) of pouches80to a more rigid state. Advantageous features of this configuration include the ability to adjust the stiffness of a pouch80by adjusting the vacuum pressure, and reversibility, where the initial flexible state of the pouch80can be returned by releasing the vacuum.

FIG. 87presents a configuration of a sleeve16, where vacuum jamming pouches80are placed opposite apertures22to actively control deformation of the actuator12at the apertures22.FIG. 88presents an illustration of this concept where the soft actuator body14is pressurized; however, a portion of the soft actuator body14at one aperture22(the furthest right) is restricted because the vacuum jamming pouch80′ is under a vacuum making it stiffer than the other pouch80, which is at atmospheric pressure.

Vacuum jamming has also proven to provide effective means for gripping an object, as has been demonstrated by Cornell University and Empire Robotics, Inc. (see, e.g. US published patent application No. 20130106127 A1). To pick up an object, a vacuum jamming gripper82, as shown inFIG. 89, with an internal pressure at atmosphere, is placed on top of the object and conforms to it. Vacuum is applied to harden the gripper82, which generates gripping forces through friction from pinching, entrapment, and vacuum suction. Furthermore, the object can be released by injecting air into the gripper82to release the vacuum.FIG. 89presents a concept where a vacuum jamming gripper82can be integrated with a sleeve16such that, depending on the task at hand, this gripping capability can be arbitrarily added to or removed from an actuator12.

FIG. 71illustrates the range of motion of a 28A durometer soft bending actuator12with 0.8-mm-thick fiber-reinforced laminates on the flat surface15of the soft actuator body14and with (a) 0 mm, (b) 15 mm, and (c) 30 mm spacing across the apertures22in the sleeves16. A soft actuator12with an extension segment70that permits localized extension is shown inFIGS. 72 and 73. In this embodiment, the extension is facilitated by a gap between sections of a substantially inelastic outer sleeve16″ and an expandable inner sleeve16′ over a soft actuator body14. Where the outer sleeve16″ is removed (producing a gap), the exposed inner sleeve16′ can radially expand and contract with fluid flow into and out of the soft actuator12. At the bending joints, apertures22can be made in both sleeves16′ and16″ without completely severing the sleeves16′ and16″ to facilitate bending of the soft actuator12at these locations. Furthermore, for actuators12that produce more than one type of motion (such as bending, extending, contracting, extending-twisting, and bending-twisting to name a few), the sleeve16can be used as a means to lock or unlock these motions.

As shown inFIGS. 74-76, the sleeve16includes an uncut portion69behind the aperture22to provide a continuous length of sleeve material at each of the bending/pivot locations. A linearly extending soft actuator body14contained in a sleeve16with a plurality of apertures (slits)22configured to generate bending of the actuator about a plurality of axes with different orientations is shown inFIG. 77; and a linearly extending soft actuator body14converted into a bending actuator by a sleeve16with a plurality of apertures22that share a common orientation and consistent spacing there between is shown inFIG. 78.

A power grip glove72including a curling soft actuator12for each finger is shown inFIGS. 79 and 80, wherein each actuator12includes a linearly extending soft actuator body14contained in a sleeve16having a plurality of apertures22to convert the linear actuation of the soft actuator body14to a bending/curling motion. The position of the apertures22can be customized to align with the location of the wearer's joints. The elasticity of the soft actuator body14allows the actuator12to extend at joints to, e.g., maintain contact (without slipping) with a bending finger with which the actuator12is in contact. In other embodiments, the actuators12can be incorporated into another type of wearable apparel, wherein the actuators12can be configured along other joints and designed to generate greater or lesser force, as needed. Control electronics can also be incorporated into the apparel for controlling the pump18and thereby controlling actuation of the actuators12.

In some applications, the actuator12can be disposable (e.g., discarded after a specified period of use, such as after one month of use) and replaced, while retaining the pump18for long-term reuse.

In other embodiments, the soft actuators12can be used independently (e.g., to create robotic hand) without joining the soft actuators12to a body part of a human or other organism. For example, a plurality of actuators12can extend from a hub to form a grasper that can pick up and manipulate objects in an environment that may be inhospitable to humans (e.g., at great depths, such as 200 meters deep or more, undersea).

In particular embodiments, the soft actuator body14can be provided on a reel, as shown inFIG. 81, and cut to a desired length. Using this embodiment, soft actuators12can be rapidly assembled by cutting the desired length of soft actuator body14from a reel and then capping the ends of the resulting soft actuator bodies14, as shown inFIG. 82. At least one of the end caps68illustrated inFIG. 82includes an embedded pneumatic or hydraulic connection passing there through (and to which a pneumatic or hydraulic pump18coupled with a fluid source is connected) to allow fluid to be pumped into the soft actuator body14to power its actuation; and a sleeve16can be fitted over the soft actuator body14with apertures22to allow for bending or curving of the actuator,12as desired.

In additional embodiments, the sleeve16can be formed of a material that is anisotropic to provide the actuator12with different properties (e.g., different strain characteristics) along different axes. Additionally, the sleeve16can be formed of a woven material that can then be made rigid by coating it with an epoxy or polyurethane. Further still, sleeves16can be applied to monolithic soft actuator bodies14that contain a plurality of air chambers. In still more embodiments, the sleeve16can include an electronic sensor [e.g., electromyography (EMG)] configured to detect signals (e.g., electrical signals, muscle activity) that accompany a human's effort to activate muscles to generate movement, which can then be mechanically assisted by the soft actuator12of this disclosure.

In describing embodiments of the invention, specific terminology is used for the sake of clarity. For the purpose of description, specific terms are intended to at least include technical and functional equivalents that operate in a similar manner to accomplish a similar result. Additionally, in some instances where a particular embodiment of the invention includes a plurality of system elements or method steps, those elements or steps may be replaced with a single element or step; likewise, a single element or step may be replaced with a plurality of elements or steps that serve the same purpose. Further, where parameters for various properties or other values are specified herein for embodiments of the invention, those parameters or values can be adjusted up or down by 1/100th, 1/50th, 1/20th, 1/10th, ⅕th, ⅓rd, ½, ⅔rd, ¾th, ⅘th, 9/10th, 19/20th, 49/50th, 99/100th, etc. (or up by a factor of 1, 2, 3, 4, 5, 6, 8, 10, 20, 50, 100, etc.), or by rounded-off approximations thereof, unless otherwise specified. Moreover, while this invention has been shown and described with references to particular embodiments thereof, those skilled in the art will understand that various substitutions and alterations in form and details may be made therein without departing from the scope of the invention. Further still, other aspects, functions and advantages are also within the scope of the invention; and all embodiments of the invention need not necessarily achieve all of the advantages or possess all of the characteristics described above. Additionally, steps, elements and features discussed herein in connection with one embodiment can likewise be used in conjunction with other embodiments. The contents of references, including reference texts, journal articles, patents, patent applications, etc., cited throughout the text are hereby incorporated by reference in their entirety; and appropriate components, steps, and characterizations from these references may or may not be included in embodiments of this invention. Still further, the components and steps identified in the Background section are integral to this disclosure and can be used in conjunction with or substituted for components and steps described elsewhere in the disclosure within the scope of the invention. In method claims, where stages are recited in a particular order—with or without sequenced prefacing characters added for ease of reference—the stages are not to be interpreted as being temporally limited to the order in which they are recited unless otherwise specified or implied by the terms and phrasing.