Patent Description:
Most robots are constructed using so-called "hard" body plans; that is, a rigid (usually metal) skeleton, electrical or hydraulic actuation, electromechanical control, sensing, and feedback. These robots are successful at the tasks for which they were designed (e.g., heavy manufacturing in controlled environments) but have severe limitations when faced with more demanding tasks (for example, stable motility in demanding environments): tracks and wheels perform not as efficiently as legs and hooves.

Evolution has selected a wide range of body plans for mobile organisms. Many approaches to robots that resemble animals with skeletons are being actively developed: "Big Dog" is an example. A second class of robot-those based on animals without skeletons-are much less explored, for a number of reasons: i) there is a supposition that "marine-like" organisms (squid) will not operate without the buoyant support of water; ii) the materials and components necessary to make these systems are not available; iii) the major types of actuation used in them (for example, hydrostats) are virtually unused in conventional robotics. These systems are intrinsically very different in their capabilities and potential uses than hard-bodied systems. While they will (at least early in their development) be slower than hard-bodied systems, they will also be more stable and better able to move through constrained spaces (cracks, rubble), lighter, and less expensive.

Robots, or robotic actuators, which can be described as "soft" are most easily classified by the materials used in their manufacture and their methods of actuation. Pneumatic soft robotic actuators can be manufactured using inextensible materials, which rely on architectures such as follows. McKibben actuators, also known as pneumatic artificial muscles (PMAs), rely on the inflation of a bladder constrained within a woven sheath which is inextensible in the axis of actuation. The resultant deformation leads to radial expansion and axial contraction; the force that can be applied is proportional to the applied pressure. Related actuators are called pleated pneumatic artificial muscles.

There are "soft" robotic actuators such as shape memory alloys which have been used both as the actuation method and as the main structural component in robots which can both crawl and jump. Another approach, which can be described as "soft" uses a combination of traditional robotic elements (an electric motor) and soft polymeric linkages based on Shape Deposition Manufacturing (SDM). This technique is a combination of 3D printing and milling. An example of a composite of traditional robotics with soft elements has been used with success in developing robotic grippers comprising soft fingers to improve the speed and efficiency of soft fruit packing in New Zealand.

Soft robotics using interconnected channels in a molded elastomeric have been reported. Soft robotics can be actuated using pneumatic pressure to cause the robot to undergo a range of motions. The basic soft robotic actuator includes an extensible channel or bladder that expands against a stiffer or less extensible backing. See, PCT Appln. No. <CIT> for additional information on the design and actuation of soft robotics.

Molding is one way to make soft robotic actuators; however, it is a batch process. There thus remains a need for low cost, simple, and high throughput methods for making soft robotics. There also remains a need for new, simple, and efficient designs for soft robotic actuation devices.

Described herein are soft composite actuators which can be produced easily and efficiently. The soft composite actuator as disclosed herein can be manufactured by bonding two or more material layers or sheets together. The material layers may be bonded together to form one or more bladder configured to hold pressurized fluid. The soft composite actuator may be actuated when the bladder therein is pressurized by infusing fluids into the bladder. The bonding may be achieved by mechanical, thermal, and/or chemical means or combination thereof. The soft composite actuator as disclosed herein can be manufactured without using any mold.

In some embodiments, one of the material layers is made of a thermoplastic elastomer material which can be thermally bonded (or high frequency welded or ultrasonically welded) together with other layers to define the actuator's bladder (e.g., air tight bladders). These constructions could also be achieved with chemical and mechanical bonds or a combination thereof. Methods of making and using the soft composite actuator are also disclosed herein.

According to the present invention, there is provided a soft composite actuator, a soft actuating device, a method of actuation and a method of making a soft composite actuator in accordance with the appended claims.

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 <NUM> or <NUM>%) 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 <NUM> 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 term "laminate" and "soft composite actuator" may be used interchangeably.

The invention is described with reference to the following figures, which are presented for the purpose of illustration only and are not intended to be limiting. In the Drawings:.

Described herein are soft composite actuators made by bonding two or more material layers. A material layer, as used herein, may refer to an elastomeric layer, a strain limiting layer, a radially constraining layer, or a first or second composite layer including one or more elastomeric sections and one or more radially constraining sections. The elastomeric layer, as used herein, refers to a layer which is made of one or more elastic materials and can be bent, curved, twisted, or subjected to any other motion to change its shape and/or orientation under pressure. Non-limiting examples of the elastic material include elastic polymer (e.g. urethanes and silicones), thermoplastic elastomers (TPEs), thermoplastic urethanes (TPUs) and so forth. As used herein, "elastomeric" and "elastic" are used interchangeably.

In some embodiments, the material layer is a strain limiting layer. The strain limiting layer, as used herein, refers to any layer which is not elastic or less elastic than the elastomeric layer. As a result, under actuation (e.g., pressurization of the bladder), the changes in the shape or orientation of the elastomeric layer, not that of the strain limiting layer, will predominantly determine the shape, curvature, and/or orientation of the soft composite actuator after actuation. In some embodiments, the strain limiting layer is made of one or more strain limiting materials. Non-limiting examples of the strain limiting material include fibers, thread, non-woven materials, and higher duromoter materials to name a few. Any other materials known in the art suitable as the strain limiting material can be used.

In other embodiments, the material layer is a radially constraining layer which limits the radial expansion of the resulting bladder and promotes efficient bending. In some specific embodiments, the radially constraining layer can have strain limiting properties such as those of the strain limiting layer. The radially constraining layer employs the strain limiting material to restrict the radial expansion of the bladder in the soft composite actuator. In one or more embodiments, the radially constraining layer is a sheet of high durometer material that contains openings, e.g., cutouts, which provide radially constraining regions (e.g., strips or bands) of spaced at locations to allow portions of the adjacent elastomeric layer to expand through the cutouts. The radially constraining regions are positioned and arranged (e.g., as bands or stripes traversing the width of the soft composite actuators) so that the elastomeric layer's radial expansion will be limited or restricted. In some embodiments, the radially constraining regions are evenly or unevenly distributed in the radially constraining layer. In some specific embodiments, the radially constraining regions, e.g., strips <NUM> in <FIG>, are oriented parallel to one of the edges of the radially constraining layer or at an angle to one of the edges of the radially constraining layer. The angle (θ) can be in any ranges or have any values. In some embodiments, θ is about <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> degree, or in any ranges bound by any two of the values disclosed herein.

In some specific embodiments, the radially constraining layer or section restrict the radial swelling of the bladder or elastomeric layer to promote more efficient bending of the actuator by supporting linear extension of the elastic layer and limiting radial expansion, which does not promote bending. In still other embodiments, the radially constraining region can be incorporated into a layer containing other materials. By way of example, the radially constraining layer or strain limiting layer can be a monolithic composite layer, e.g., layer <NUM> in <FIG>, comprising one or more elastomeric sections and one or more radially constraining sections. The elastomeric section may be made of elastomeric materials and the radially constraining section may be made of strain limiting materials.

In certain embodiments, the radially constraining layer comprises one or more individual radially constraining sections, which can be assembled and bonded to form a radially constraining layer. In certain specific embodiments, the radially constraining sections comprise radially constraining strips evenly or unevenly distributed in the radially constraining layer. The radially constraining strips, e.g., strips <NUM> in <FIG>, may be oriented parallel to one of the edges of the radially constraining layer or at an angle to one of the edges of the radially constraining layer. The angle (θ) can be in any ranges or have any values. In some embodiments, θ is about <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> degree, or in any ranges bound by any two of the values disclosed herein. The radially constraining strips may be bonded to the first elastomeric layer.

In some embodiments, the material layer is a radially constraining layer described above.

The two or more material layers are bonded together to form sealed at least one bladder for holding pressurized fluid. In some embodiments, the perimeters or certain portions of two adjacent material layers in the soft composite actuator are bonded together to result in a fluid-tight bladder, except that the bladder may be connected to a fluid infusion/vacuum source. In certain embodiments, the perimeters or certain portions of the adjacent elastomeric layer and the strain limiting layer in the soft composite actuator are bonded together to result in a fluid-tight bladder. In other embodiments, the perimeters or certain portions of the adjacent first composite layer and the strain limiting layer in the soft composite actuator are bonded together to result in a fluid-tight bladder. In still other embodiments, the perimeters or certain portions of the adjacent first composite layer and the second composite layer in the soft composite actuator are bonded together to result in a fluid-tight bladder. In still other embodiments, the soft composite actuator comprises two elastomeric layers and the perimeters or certain portions of the two adjacent elastomeric layers are bonded together to result in a fluid-tight bladder.

In other embodiments, the radially constraining layer comprises one or more strain limiting sections free from any openings. Thus, the radially constraining layer may include one or more openings through which one or more portions of the adjacent first elastomeric layer expand upon actuation, and one or more strain limiting sections free from any openings. Upon actuation, such soft composite actuator may bend at the portion of the radially constraining layer having the openings and may stiffen at the portion of the radially constraining layer free from any openings.

In some embodiments, the bladder is airtight except its connection to an external fluid source to infuse pressurized fluid into the bladder. Non-limiting examples of the fluids include a gas and a liquid. Non-limiting examples of the fluid source include a gas tank, a gas cylinder, a liquid pump, compressor, gases given off by a chemical reaction, and so forth. The gas may be air, nitrogen, or one of the inert gases. The liquid may include water, aqueous solution, and organic solvents or solutions. Upon actuation (e.g., when the bladder is infused with pressurized fluid), the soft composite actuator may actuate in a pre-determined way to change the actuator's shape, size, orientation, and/or curvature, to achieve one or more desirable functions. The soft actuator may have one bladder or a plurality of bladders connected to the same or different fluid sources.

In an unclaimed aspect, a soft composite actuator is described, including comprising:.

The strain limiting layer may be located at the top or bottom of the soft composite actuator. The layered soft composite actuator allows for the control of the direction of expansion. For instance, <FIG> show that the soft composite actuator can be constructed by layering materials of different elasticity and subtracting material (e.g., elastomeric layer, strain limiting layer, and radially constraining layer).

The actuation mechanism of the soft composite actuator is first described with reference to <FIG>. As shown in <FIG>, an elastic layer <NUM> and a strain limiting layer <NUM> are bonded at the layers' perimeter <NUM>. The bonding may be achieved thermally, mechanically, and/or chemically. In some embodiments, the elastic layer is made of elastic polymers which can be thermally bonded to other layers such as the strain limiting layer. The term "elastic layer" or "elastic section" (described below), as used herein, refers to any material layer or section made of material having elastic properties and can bend or expand under pressure. The term "strain limiting layer", as used herein, refers to any material layer which is not elastic or less elastic than the elastic material forming the elastic layer or the elastic section in the composite layer described below. The bonding of the elastic layer <NUM> and the strain limiting layer <NUM> results in the formation of an airtight bladder <NUM>, which is sealed off except its connections to an outside fluid infusion/vacuum source configured to inflate or deflate the bladder by infusing and removing the fluid in and out of the bladder.

Thus, when two different material layers (i.e., one elastic layer <NUM> and one strain limiting layer <NUM>) are bonded to form a bladder, the resulting structure <NUM> has an anisotropic response to pressurized fluid in the bladder. The elastic layer <NUM> expands while the strain limiting layer <NUM> undergoes limited expansion. The difference in strain responses between the two layers may cause the structure to bend in the direction of the strain limited layer (<FIG> illustrates the soft composite actuator with a bladder <NUM> partially filled by pressured fluid from the fluid infusion/vacuum source <NUM>. The partially filled bladder has an inside pressure higher than the outside pressure (Δp) so that the elastic layer <NUM> is curved. When the bladder is fully filled by the pressured fluid, the linear growth of the portion of the elastic layer forming the inflated air tight bladder (portion <NUM> in <FIG>) will eventually cause the strain limited layer <NUM> to bend. The circumferential constraint, i.e., the bonding at the perimeter <NUM>, is beneficial because without such circumferential constraints, the material layer has considerable radial growth which after a certain point (e.g., when the material approaches its yield stress or fatigue yield stress), is not useful for the purposes of the bending.

A soft composite actuator according to one or more embodiments is described with reference to <FIG>. As shown in <FIG>, an elastomeric layer <NUM> is disposed between a radial constraining layer <NUM> and a strain limiting layer <NUM>. The perimeters of layers <NUM>, <NUM>, and <NUM>, e.g., portion <NUM> are bonded together thermally to result in soft composite actuator <NUM>, which upon actuation bends in a predetermined fashion (<FIG>). The bonding may also be achieved by chemical method, mechanical method, and a combination thereof. One of the advantages of the instant application is that the soft composite actuator described herein can be made without using any mold, thus the manufacture process is greatly simplified. In some embodiments, heat can be applied to two or more material layers, e.g., elastomeric layer and strain limiting layer, to bond the layers together. In other embodiments, mechanical force by hand or machine can be applied to two or more material layers, e.g., elastomeric layer and strain limiting layer, to bond the layers together. In still other embodiments, chemical reactants can be deposited between the material layers or embedded in one or more material layers and a chemical reaction may be initiated to bond the two or more material layers, e.g., elastomeric layer and strain limiting layer, together.

As shown in <FIG>, the soft composite actuator <NUM> contains a bladder formed by the bonding of the perimeters of layers <NUM> and <NUM>. This bladder (<NUM> in <FIG>) is connected to an infusion/vacuum source <NUM> to infuse pressurized liquid into bladder <NUM>. The fluid-filled bladder has an inside pressure higher than the outside pressure (Δp) which forces the elastomeric layer <NUM> and the radially constraining layer <NUM> to bend towards the strain limiting layer <NUM>.

Thus, as shown in <FIG>, an additional layer, i.e., the radially constraining layer, can be added to create an additional anisotropic response by limiting the radial expansion of the elastic layer. The cutouts (<NUM>) on the radially constraining layer allow the elastic layer to expand lengthwise while limiting strain limiting regions or bands <NUM> limit radial expansion. Restricting the radial swelling of the bladder promotes more efficient bending by supporting linear extension of the elastic layer and limiting radial expansion, which does not promote bending. It should be noted that additional layers could be added to include other functionalities such as super absorbent material to soak up fluids, antibacterial properties, hot therapy, and cold therapy.

The soft composite actuator can be designed and configured to actuate in a predetermined manner upon pressurization of the bladder and/or perform one or more desirable functions. Upon actuation, the soft composite actuator may be designed to generate structural anisotropy or structural isotropy. That is, the soft composite actuator may upon actuation generate the same or different structural changes when measured along different axes of the soft composite actuator.

In some embodiments, the soft composite actuator further includes a second elastomeric layer, and a bladder can be formed by, for example, thermally sealing the edges of the two elastomeric layers. In some embodiments, the strain limiting layer in the soft composite actuator is also a radially constraining layer which limits the radial expansion of the elastomeric layer. These designs are described with reference to <FIG>, which show a linear extending actuator including two radially constraining layers and two elastic layers bonded to form a linear extending actuator.

As shown in <FIG>, a first and second elastomeric layers, <NUM> and <NUM>, respectively, are sandwiched between a first radially constraining layer <NUM> and a strain limiting layer (i.e., a second radially constraining layer <NUM>). The radially constraining layers <NUM> and <NUM> contain cutouts <NUM> and <NUM>, respectively. After layers <NUM>, <NUM>, <NUM>, and <NUM> are bonded at their perimeters, e.g., edge <NUM>, to form composite <NUM>, some portions of the soft composite actuator, e.g., portions <NUM> and <NUM>, can be cut off along the dotted lines shown in <FIG> to form soft composite actuator <NUM>. These excess materials from the radially constraining layers <NUM> and <NUM> are removed leaving strain limiting strips <NUM> bonded to the elastic layers. <FIG> is a cross-section view of the soft composite actuator <NUM> without (upper portion of <FIG>) and with fluid pressurization (lower portion of <FIG>). As shown in <FIG>, the soft composite actuator has layers <NUM>, <NUM>, <NUM>, and <NUM> bonded together at the edge <NUM>. Upon actuation, bladder <NUM> between layers <NUM> and <NUM> is pressurized to generate an inside pressure of P<NUM>, which is greater than the outside pressure Patm. As a result, the layers of the actuator <NUM> curve as shown in the lower portion of <FIG>.

<FIG> is a perspective view of the linear extending actuator <NUM> in an unpressurized state. Edges of the layers, e.g., <NUM> and <NUM>, are bonded (<FIG> is a perspective view of the linear actuator <NUM> in the actuated state extending under fluid pressurization where the strain limiting strips <NUM> in the radially constraining layer <NUM>, connected by the bond at edge <NUM>, form radially constraining hoops along the length of the actuator, and thus promote linear extension along the direction of axis <NUM>. <FIG> demonstrates that when the orientation of the strain limiting strips <NUM> run length wise, i.e., along axis <NUM>, the resulting soft composite actuator is a contracting linear actuator <NUM>, (i.e. the largest deformation is contractile). <FIG> shows the contracting linear actuator <NUM> in its unactuated state (upper left corner of <FIG>) and actuated state (lower right corner of <FIG>).

In certain embodiments, the pressurized fluid is temperature-regulated to deliver hot or cold therapy. For instance, fluidic lines could also be heat stamped into a material layer for delivery hot and/or cold therapy or even medicine.

As shown in <FIG>, the elastomeric layer, the strain limiting layer, and the radially constraining layer may have a planar shape before or during bonding. In some other embodiments, at least of the elastomeric layer, the strain limiting layer, and the radially constraining layer may have a non-planar shape before or during bonding.

In one or more embodiments, one or more layers of the soft composite actuator can be preformed into a non-planar shape before assembly. <FIG> is an exploded view of a bending soft composite actuator including layers that are preformed to a particular shape before or during assembly so that the actuator takes on a non-planar profile in its unpressurized state. The soft composite actuator includes the pre-formed radially constraining layer <NUM>, a pre-formed elastic layer <NUM>, and a strain limiting layer <NUM>. These material layers are bonded at the perimeters of the material layers, e.g., perimeter <NUM> to form a bending soft composite actuator <NUM> (<FIG>). The bladder formed in the actuator <NUM> is connected to a pressurized fluid source via a tube <NUM>. Other types of connection known in the art are contemplated. <FIG> is a perspective view of the assembled bending actuator <NUM> in its unpressurized state. <FIG> is a side view of the bending actuator in a pressurized state. When the actuator <NUM> is actuated by infusion of pressurized fluid through tube connection <NUM>, radially constraining layer <NUM> restricts the radial expansion of the elastic layer <NUM> and actuator <NUM> bends in a predetermined matter, i.e., towards the direction of strain limiting layer <NUM>.

Thus, in some embodiments, it may be advantageous to pre-form (e.g., thermally form) one or more material layers, e.g., radially constraining layer, first and second composite layers (also referred to anisotropic layer in <FIG>), elastic layer, or strain limiting layer, before or during actuator assembly so that an actuator can be designed to achieve a particular thickness (or pressurized profile) under fluid pressurization. In some embodiments, preforming one or more materials is desirable for a soft composite actuator to achieve desired range of motion, stiffness, and force production as these outputs are linked to actuator thickness. Pre-forming to a non-planar initial state may also place less strain on the material to reach a target state, which in turn, may reduce the required input pressure and material fatigue. Non-limiting examples of the non-planar shapes of the material layers include half cylinder shape (<FIG>), rectangular, tapered, and bellows-shaped. Any material layer of any of the soft composite actuator may be pre-formed.

In another aspect, a soft composite actuator is described, including:.

The first composite layer is located at the top or bottom of the soft composite actuator. In some embodiments, the first elastomeric section, the first radially constraining section, and/or the first composite layer have the same thickness. In these embodiments, the first composite layer can be made by from bonding the first elastomeric sections and the first radially constraining sections together. In other embodiments, the first elastomeric section and the first radially constraining section have different thickness. In these embodiments, the first composite layer and the first elastomeric section may have the same thickness. In some specific embodiments, the first elastomeric section is thicker than the first elastomeric section and/or the first elastomeric section encapsulates the first radially constraining section.

The soft composite actuator according to this aspect is described with reference to <FIG>. <FIG> is an exploded and assembled view of an unclaimed soft composite actuator <NUM> capable of bending and including a first composite layer <NUM>. The first composite layer <NUM> has radially constraining sections <NUM> made of strain limiting materials and elastomeric section <NUM> made of elastic materials. Sections <NUM> and <NUM> can be in any shape or size and are bonded together by thermal, chemical, and/or mechanical methods to form the monolithic first composite layer <NUM>. Because the first composite layer <NUM> has different expansion properties or characteristics along the x and y axes (i.e., layer <NUM> may expand more easily along the y axis than alone the x axis), the first composite layer <NUM> is also referred to as a monolithic anisotropic layer. As shown in <FIG>, sections <NUM> and <NUM> both have the same thickness as that of the monolithic layer. The first composite layer is then bonded with a strain limiting layer <NUM> to form the bending soft composite actuator <NUM>.

Thus, in the embodiments described in <FIG>, the first composite layer <NUM> has anisotropic properties such that it prefers to stretch along the y-axis and is strain-limited along the x-axis. The strain limiting layer <NUM> is made of strain limiting material and strain-limited is both the x and y directions. The layers are bonded together at the two layers' perimeters such that the bond defines a fluid tight (e.g., airtight or water tight) bladder.

<FIG> is a side view of the bending soft composite actuator <NUM> upon actuation when the bladder <NUM> is under fluid pressurization. The anisotropic layer <NUM> performs a dual function of promoting linear growth of the elastic sections <NUM> while limiting its radial expansion to cause the assembly to bend.

In some embodiments, the strain limiting layer includes or is a second composite layer comprising one or more second elastomeric sections and one or more second radially constraining sections, wherein the second elastomeric section, the second radially constraining section, and the second composite layer have the same or different thickness, wherein the second composite layer is a monolithic anisotropic layer. Similar to the first composite layer, the second elastomeric section and the second radially constraining section can be bonded together to form the second composite layer. Alternatively, the second radially constraining section may be encapsulated in the second elastomeric section. The radially constraining sections may be evenly or unevenly distributed in the composite layer. In some embodiments, the radially constraining sections comprise radially constraining strips oriented parallel to one of the edges of the composite layer or at an angle to one of the edges of the composite layer. The angle (θ) can be in any ranges or have any values. In some embodiments, θ is about <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> degree, or in any ranges bound by any two of the values disclosed herein. The soft composite actuator according to these embodiments is described with reference to <FIG>.

<FIG> is a perspective view of an assembled linear extending soft composite actuator <NUM> which consists of two anisotropic layers <NUM> and <NUM> bonded together to form an airtight (or water tight) bladder. The first composite layer <NUM> contains radially constraining sections <NUM> made of strain limiting materials and elastomeric section <NUM> made of elastic materials. Sections <NUM> and <NUM> are bonded together by thermal, chemical, and/or mechanical methods to form the monolithic first composite layer. Sections <NUM> and <NUM> both have thickness the same as that of the first composite layer <NUM>.

The strain limiting layer <NUM> in <FIG> is also a second composite layer containing radially constraining sections <NUM> made of strain limiting materials and elastomeric section <NUM> made of elastic materials. Sections <NUM> and <NUM> are bonded together by thermal, chemical, and/or mechanical methods to form the monolithic first composite layer. Sections <NUM> and <NUM> both have thickness the same as that of the first composite layer <NUM>.

Both layers <NUM> and <NUM> are anisotropic layers. <FIG> is a side view of the linear extending actuator <NUM> before actuation (top portion of <FIG>) and under fluid pressurization (lower portion of <FIG>) where the strain limiting sections (<NUM> and <NUM>) of the anisotropic layers <NUM> and <NUM> form hoops that limit radial expansion and promote linear extension. As shown in <FIG>, upon actuation the actuator extends a distance of ΔL.

Thus, in these embodiments described above, the complexity of bonding multiple material layers can be reduced by creating the desired anisotropic properties into a single layer, e.g., the first or second composite layer. The strain limiting sections (made of a strain limited material such as fibers, thread, non-woven materials, higher duromoter materials, etc.) can be combined with the elastic sections to create a single, monolithic layer that is more elastic in one direction (e.g., y-direction in <FIG>) over another (e.g., x-direction in <FIG>). When this anisotropic layer is bonded to the strain limited layer the result is a bending actuator constructed from only two material layers. The anisotropy contained in a single layer can be achieved several ways including molding or encapsulating the strain limited material in the elastic material, heat stamping the strain limited material together with the elastomer, sandwiching two elastomer films around the strain limited material, or cast extruding elastic and strain limiting materials together. Furthermore, adjusting the spacing and orientation of the elastic and strain limiting materials in the anisotropic layer can enable the soft actuator to combine multiple actuations in series such as stiffening sections, bending sections, linear extending sections, linear extending and twisting, and bend-twist sections (see, e.g., <FIG> for an example actuator with stiff sections and bending sections). Similarly, the anisotropic layer can be bonded with another anisotropic layer to make a linear actuator (extending and contracting).

<FIG> show that the direction of expansion can be controlled by combining elastic material and strain limiting material into one monolithic layer, which contains the elastomeric sections and the radially constraining sections. In some embodiments, the elastomeric sections and the radially constraining sections are cast extruding together, or embed fiber reinforcements could be used to create the strain limiting property. The various applications and variations described with particularity for the multilayer versions of the composite layer actuator can also be achieved using the combined elastomer/strain limiting material arrangement in a monolithic layer.

In some embodiments, the radially constraining section comprises a radial strain strip oriented parallel to one of the edges of the first or second composite layer (see, e.g., <FIG> and <FIG>).

In other embodiments, the radially constraining section comprises a radial strain strip oriented at an angle to one of the edges of the composite layer. For instance, <FIG> is an exploded and assembled view of an unclaimed soft composite actuator <NUM> capable of bending and twisting under fluid pressurization. As illustrated in <FIG>, a monolithic first composite layer <NUM> is provided, containing radially constraining sections <NUM> made of strain limiting materials and elastomeric sections <NUM> made of elastic materials. Sections <NUM> and <NUM> are bonded together by thermal, chemical, and/or mechanical methods to form the monolithic first composite layer <NUM>. Sections <NUM> and <NUM> both have thickness the same as that of the first composite layer <NUM>. As shown in <FIG>, the radially constraining section <NUM> is in the form of a radially constraining strip, which is oriented in an angle (θ) with respect to the layer <NUM>'s horizontal edge (shown as the y axis). θ can be in any ranges or have any values. In some embodiments, θ is about <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> degree, or in any ranges bound by any two of the values disclosed herein. The angled elements, e.g., <NUM> or <NUM>, in the anisotropic layer <NUM> can be evenly spaced, intermittently spaced, and/or at a gradient of angles. Angling the elastic and strain limited elements in the anisotropic layer promotes linear growth at an angle to the y-axis. As a result, when layer <NUM> is combined with a strain limiting layer, e.g., <NUM>, the resulting actuator <NUM> will simultaneously bend and twist upon actuation.

<FIG> is an exploded and assembled view of an actuatable device capable of linear extension and twisting under fluid pressurization by bonding two anisotropic layers with angled elastic and strain limiting elements. A first composite layer <NUM>, containing radially constraining sections <NUM> (with an angle θ with respect to the layer <NUM>'s horizontal edge) and elastic sections <NUM>, is combined with a second composite layer <NUM>, which contains similar elastic section <NUM> and radially constraining section <NUM>, to form a soft composite actuator <NUM>. When actuated, soft composite actuator <NUM> extends linearly and twists.

In some embodiments, the soft composite actuator stiffens when actuated and thus can be termed a stiffener. <FIG> shows the top view of an unactuated stiffener soft composite actuator <NUM> (top portion of <FIG>) and the response of the actuator when actuated (bottom portion of <FIG>) under fluid pressurization. The radially constraining layer <NUM> of the actuator <NUM> contains cutout section <NUM> and solid sections <NUM>. In this arrangement, the cut outs define areas where the actuator is allowed to bend and the solid sections, e.g., <NUM>, of the radially constraining layer restrict any actuation by inflating to form a pressurized tube termed a stiffener.

<FIG> is an extension of <FIG> demonstrating that several bending joints <NUM> can be designed into a single actuator. In this illustration, the actuator <NUM> contains solid sections <NUM> (which stiffen upon actuation) and cutout sections <NUM> (which allow the actuator to bend during actuation) in its radially constraining layer <NUM>. As a result, this closed loop actuator <NUM> could be used to wrap around an object or to create an opening.

<FIG> is an extension of <FIG> demonstrating that multiple bending actuators can be combined on a single laminate. In this figure, actuator <NUM> contains four individual bending actuators which are arranged to form a grasping device. The actuator <NUM> has a radially constraining layer <NUM> which contains openings, e.g., cutout sections <NUM> and solid sections <NUM>. The bottom portion of <FIG> shows the scenario where three digits are activated when the bladder of the actuator is connected to a pressurized fluid source via a tubing connection, while one is not connected to the pressurized fluid source or is connected to a different pressurized fluid source. In this figure, four individual bending actuators are arranged to form a grasping device. As a result, the three digits and the fourth digit can be controlled separately.

The locations of the openings, e.g., cutout sections and solid sections can be adjusted and arranged in any predetermined matter to achieve a desired actuation, e.g., any preferred ranges of motion or shapes of the actuated actuator. For example, as shown in <FIG>, the radially constraining sections can be arranged to be in an angle with respect to the edge of the material layers of the actuator, which can produce simultaneous bending and twisting motion (not illustrated).

<FIG> depicts a top view and an isometric view of an actuatable device <NUM> that combines a multiple functions onto a single laminate. In this figure, two bending actuators <NUM> (having cutouts in its radially constraining layers) are connected via two stiffeners <NUM> (having solid sections in its radially constraining layers). The material layers of the actuator are bonded at perimeters such as <NUM>. Thus, on a single sheet, multiple functions can be achieved by using a single bladder. In <FIG>, the rectangular profile of the actuator <NUM> has a perimeter thermal bond and a second bond offset a certain distance inward (shown as <NUM>). On two vertical sides (<NUM>) of the rectangle the radially constraining layer has openings, e.g., cutouts that define a bending actuator while on the other two sides, i.e., the horizontal sides <NUM>, the radially constraining layer has no openings, e.g., cutouts, which under fluid pressurization becomes a stiff inflated tube that can be used to as a structural element.

<FIG> shows an actuator device <NUM> having multiple stiffeners used to support bending actuators and achieve greater coverage. In this figure, two bending actuators <NUM> (having cutouts in its radially constraining layers) are connected via four stiffeners <NUM> (having solid sections in its radially constraining layers). The material layers of the actuator are bonded at perimeters such as <NUM>. In this embodiment, the actuator can be used to generate a bending motion with greater coverage. For example this could be used as a splint that can conform to the leg while also providing stability (i.e. stiffness) along the length of the injury. In some embodiments, the single bladder of the actuator can be separated into multiple bladders for more control over each function of each section of the actuator device. For example, the stiffeners may need to be separate bladders from the bending actuator because they may operate at different pressures.

In some embodiments, the soft composite actuator further comprises one or more rigid elements attached to the strain limiting layer. Rigid elements could be added to actuator body to define discrete bending points or to rigidize certain lengths for improved force transmission or stability. In some embodiments, rigid elements also enable a tighter bending radius of curvature and can be used as mounting substrate for auxiliary equipment.

<FIG> depicts an exploded view and cross-section view of an actuatable device <NUM> that incorporates rigid elements as an additional layer. Soft actuator <NUM> contains a radially constraining layer <NUM>, an elastic layer <NUM>, a strain limiting layer <NUM>, and a rigid element layer <NUM> containing rigid elements <NUM>. These layers are stacked and bonded together to provide the actuator <NUM>.

<FIG> is a side view of the bending actuator <NUM> under fluid pressurization with rigid elements where it only bends at the gaps between the rigid elements, e.g., position <NUM>. <FIG> shows the actuator <NUM> with the four layers <NUM>, <NUM>, <NUM>, and <NUM> described above in <FIG>. Upon actuation, a portion of the elastic layer <NUM> may expand through the openings, e.g., cutouts in the radially constraining layer <NUM>. In some embodiments, the space between the rigid elements may be increased to increase the radius of curvature.

The soft composite actuator as described herein may have a variety of functions. In some embodiments, the soft composite actuator is configured to open an incision, move, displace organs, muscle, and/or bone, brace a joint, be worn to support joint movements, shape-match an object, fold pre-defined bending joints to create origami-like structures, achieve a sufficient grasp over the object, or create a padded layer conformal to the object.

In some embodiments, one of the material layers, e.g., the elastic layer, is pre-strained before being bonded to the radially constraining layer and/or the strain limiting layer. Pre-straining the elastic layer could be used to create a bimorph bending actuator. This could be used as a way to make graspers that are low profile when unpressurized and can conform around an object when pressurized. Any other type of material layer can be pre-strained as well.

<FIG> shows the assembly of a bimorph bending actuator that incorporates a pre-strained layer during the assembly. The elastic layer <NUM> is pre-strained along the directions of <NUM> and <NUM>, before being bonded to the radially constraining layer <NUM> and the strain limiting layer <NUM>. <FIG> shows the range of motion of the bimorph bending actuator <NUM> at different stages of pressurization. Under no fluid pressurization (state <NUM>), the pre-strained elastic layer causes the actuator <NUM> start in a curled position. Under partial fluid pressurization (state <NUM>), the actuator <NUM> uncurls and straightens out. When the actuator is fully pressurized (state <NUM>), it curls to the opposite side.

<FIG> illustrates that the opposing bimorph bending actuators can be used to form a grasper <NUM>. At the unpressurized state <NUM>, the grasper curls and does not grab object <NUM>. At the partially actuated state <NUM>, the grasper <NUM> only partially grabs object <NUM>. Finally, when the grasper <NUM> is fully pressurized (state <NUM>), object <NUM> is tightly surrounded by the grasper <NUM>. Similarly a bimorph bending actuator can also be created with two opposing bending actuators that are bonded together (or share the same strain limiting layer).

In some embodiments, the soft composite actuator is a multi-degree-freedom bending actuator. In some specific embodiments, the degree of the actuation, e.g., bending of the soft composite actuator may be controlled and fine-tuned by the fluid pressure inside the bladder. In some embodiments, the soft composite actuator is attached to one or more pneumatic or hydraulic connections. For instance, the pneumatic or hydraulic connections connected to the bladder, e.g., a fluid pump, may apply different pressures to the fluid so result in different degrees of actuation, e.g., bending.

<FIG> are an extension of <FIG> where multiple linear extending actuators can be grouped on the same laminate to form a multi-degree of freedom bending and extending actuator. In these figures, two anisotropic layers (first composted layer <NUM> and second composite layer <NUM> in <FIG>) are bonded together at locations shown as <NUM> such that they form three different bladders, <NUM>, <NUM>, and <NUM>. Each of the first and second composite layers has elastic sections <NUM> and radially constraining sections <NUM>. After bonding, three linear actuators, <NUM>, <NUM>, and <NUM> are formed.

<FIG> is an end view of <FIG> (upper portion of <FIG>) and depicts the next stage in the fabrication of a multi-degree of freedom bending and extending actuator where the laminate is bonded end to end to form a tube shape (lower portion of <FIG>) at end <NUM>.

<FIG> illustrates that when one bladder of the actuator is selectively pressurized it will linearly extend causing the tube structure to bend to an angle θ (scenario <NUM>). Fluid pressurization of one or more chambers/bladders causes bending and some linear extension. On the other hand, equal pressurization of the all the bladders will cause the actuator to only extend linearly (scenario <NUM>). Note that in scenario <NUM>, only one of the bladders is pressurized to have a pressure P<NUM>, which is greater than the outside atmosphere pressure. In scenario <NUM>, all of the three bladders are equally pressurized to have pressures P<NUM>, P<NUM>, and P<NUM>, which are greater than the outside atmosphere pressure.

In some embodiments, the soft composite actuator as described herein may be used for stabilizing a limb. In some embodiments, the soft composite actuator is part of a splint or is the splint. In other embodiments, the soft composite actuator is part of a grasper comprising a plurality of digits, or is grasper.

<FIG> is a perspective view of a wearable application where soft actuators have been incorporated into a glove <NUM> to assist joint motions. The glove <NUM> contains cutouts <NUM> in its radially constraining layer to accommodate the finger joint bending. The material layer-bonding approach enables the integration of a network of soft actuators that can apply torques to finger joints to support hand closing. A similar configuration on the palm side could assist opening the hand. With this approach, the material layers can serve a dual function of forming the actuators and serving as the glove material.

In some embodiments, one of material layers, e.g., the elastomeric layer, the strain limiting layer, the first and second composite layer (described below), and/or the radially constraining layer, is configured to have one or more functions selected from the group consisting of absorbing fluids, transmitting light, changing color or luminescence, embedding a soft sensor, embedding a medical patch, embedding at least a part of an electronic circuit, embedding a heating element, and a combination thereof.

<FIG> is perspective view of a material layer described herein demonstrating multi-functionality. In some embodiments, any of the material layers described herein can incorporate electronics, heating elements, sensors, and so forth. As shown in <FIG> (left portion), a heating element <NUM> may be incorporated into a material layer <NUM>, e.g., a strain limiting layer. Also shown in <FIG> (right portion), a circuit board or electronic element <NUM> can be incorporated (e.g., printed) into a material layer <NUM>, e.g., a strain limiting layer. Any of the material layers described herein can have sensing capabilities by incorporating flex sensors, inertial measurement units (IMUs), or soft sensors into the material layers.

<FIG> shows a sequence of side views of an actuatable device <NUM> that uses connected pressurized bladders to transmit force to lift an object. In step <NUM>, the actuator <NUM> is formed by bonding multiple material layers at locations such as <NUM>. The actuator <NUM> has three bladders, <NUM>, <NUM>, and <NUM>, which are in fluidic communication with one another. In step <NUM>, a heavy object <NUM> is placed on bladder <NUM> and pressurized fluid <NUM> is infused into the bladders. Bladders <NUM> and <NUM> expand however bladder <NUM> does not expand due to the gravity force of object <NUM>. In step <NUM>, force F is applied onto bladders <NUM> and <NUM>. The force F can be applied by human or mechanical means. As a result, pressurized fluid is forced into bladder <NUM> and causes bladder <NUM> to expand and at the same time, move object <NUM> upwards for a distance ΔD. Thus, the flexible nature of the material layers enables the bladder to operate in non-planar scenarios and the fluid therein can be passed through a narrow opening, e.g., opening <NUM>.

In some embodiments, the soft composite actuator described herein can be prepared by bonding a portion of a pre-stacked laminate containing all the material layers required for the soft composite actuator. The material layers may be pre-stacked or rolled into a multi-layer laminate. When in use, a desired size of the laminate may be removed, e.g., cut, and bonded to form the soft composite actuator. In some embodiments, two or more portions of the laminate can be cut and bonded together to form a soft actuating device including two or more soft actuators descried herein.

In some embodiments, the pre-stacked laminate comprising a first elastomeric laminate layer, a strain limiting laminate layer, and a first radially constraining laminate layer. A portion of the laminate is separated to provide the first elastomeric layer, the strain limiting layer, and the first radially constraining layer stacked together. These layers may then be bonded together to provide a soft composite actuator described herein.

In some embodiments, the pre-stacked laminate comprising a monolithic, first composite and a strain limiting laminate layer. A portion of the laminate is separated to provide the first composite layer and the strain limiting layer stacked together. These layers may then be bonded together to provide a soft composite actuator described herein.

<FIG> shows a sequence of images where a rolled sheet of actuatable devices can be cut to a desired length and the bladders can be resealed with a sealing tool. In step <NUM>, a plurality of material layers bonded at locations such as <NUM> are rolled into a roll. During use, a desired portion of the roll can be cut. The newly cut edge can be sealed using a sealing tool <NUM> (step <NUM>). The cut portion can be further divided as shown in step <NUM>, where the sealed edge <NUM> remains sealed.

<FIG> illustrates how the cut portion of the material layer roll can be assembled together to form a range of different actuatable devices. In step <NUM>, bending actuator <NUM>(which contains cutouts <NUM> in its radially constraining layer) and bending actuator <NUM> (which contains cutouts <NUM> in its radially constraining layer) are joined together to a stiffening actuator <NUM> (which contains solid strain limiting sections <NUM> in its strain limiting layer). In step <NUM>, the resulting actuator device <NUM> is actuated where the bending portions (<NUM> and <NUM>) of the device bend, while the stiffening potion (<NUM>) is stiffened. These illustrations present concepts where sheets of any soft actuator described herein, e.g., bending, linear extending, contracting, bend/twist, and stiffening actuators, can be cut to length, sealed, and assembled into a range of configurations.

In certain embodiments, a packaging for holding the soft composite actuator's material layer sheet can safely transmit the thermal bonding pattern without comprising the integrity of the package seal. In some embodiments, the soft composite actuator's material layers, e.g., the elastomeric layer, the strain limiting layer, the radially constraining layer, the first composite monolithic layer, and/or the second composite monolithic layer, are contained in a package. Bonding of portions of at least two layers can be achieved by external means without the compromise of the package to form the soft composite actuator with predetermined shape. In some embodiments, the portions of at least two layers are bonded by an external heat source that passes through the packaging. In other embodiments, the package further comprises a heating element and bonding is achieved by heat generated from the activated heating element. Non-limiting examples of heating element include induction heating, chemical reaction heating, or electrical heating elements such as nichrome wire, graphite, and so forth.

<FIG> depicts a process by which the bladders of actuatable devices can be defined while the layers of the laminate are contained within packaging (both sterile and non-sterile). The figure depicts packaging that can safely transmit the thermal bonding pattern without reducing the integrity of the package seal. This concept presents a solution to meeting inventory needs. In step <NUM>, a sterile (or non-sterile) packaging <NUM> holds the material layer sheet <NUM> to be thermally bonded. The face of the packaging may contain a bonding pattern <NUM>. In step <NUM>, a bonding device is used to thermally (or chemically or mechanically) bond the desired bladder along the thermal bonding pattern <NUM> labelled on the face of the packing. Thus, in step <NUM>, thermal bond pattern (a rectangle in this case) has been transferred to the contents of the package while still maintaining the sterility of the package contents. When the soft composite actuator <NUM> is needed, it is removed from the packaging (step <NUM>).

In yet another aspect, a method of actuation is described, including:.

In some embodiments, the material layers are arranged and bonded to create structural anisotropy. In some embodiments, actuation of the soft composite actuator achieves one or more motions selected from the group consisting of bending motion, combination bending, twisting motion, linear extension, a combination of linear extension and twist, linear contraction, a combination of linear contraction and twist, and any combination thereof. In some specific embodiments, the soft composite actuator stiffens upon fluid pressurization. The bladder may be inflated to different pressures to achieve a tunable stiffness surface. The different pressures may be controlled or tuned by the external pressurized fluid source.

In yet another aspect, a soft actuating device is described, including a plurality of the soft composite actuators described in any of the embodiments herein. The plurality of the soft composite actuators may be connected to the same fluid source, or to two or more different fluid source. In certain embodiments, the soft actuating device includes a first and a second soft composite actuators described in any of the embodiments herein. The first soft actuator may be connected to a first pressurized fluid source and the second soft actuator may be connected to a second pressurized fluid source. Thus, the first and the second soft composite actuators may be actuated separately or alternately, by alternately actuating the first and second fluid sources. In some specific embodiments, the first soft actuator is a stiffener described herein. In some specific embodiments, the second soft actuator is a bending actuator described herein. Thus, the soft actuating device may be controlled to enable different motions, e.g., bending or stiffening, by actuating different fluid sources connected to the bladders of the individual soft composite actuators in the soft actuating device.

In yet another aspect, a method of making a soft composite actuator according to any of the embodiments described herein is disclosed, including:.

In some embodiments, providing a first elastomeric layer, a strain limiting layer, and a first radially constraining layer comprises providing a pre-stacked laminate comprising a first elastomeric laminate layer, a strain limiting laminate layer, and a first radially constraining laminate layer; and separating part of the laminate to provide the first elastomeric layer, the strain limiting layer, and the first radially constraining layer stacked together. Thus, the material layers of the soft composite actuator may be pre-stacked and cut and bond when needed.

In some embodiments, providing the first composite layer and the strain limiting layer comprises: providing a pre-stacked laminate comprising a first composite laminate layer and a strain limiting laminate layer; and separating part of the laminate to provide the first composite layer and the strain limiting layer stacked together.

The bonding may be achieved by a method selected from the group consisting of thermal method, chemical method, mechanical method, and a combination thereof. In some embodiments, the method further includes removing excess material from the soft composite actuator after bonding.

In yet another aspect, a method of using the soft actuator of any one of the embodiments for one or more functions is described, wherein the function is selected from the group consisting of distribute forces, mixing material, handling material, lifting, grasping, steering a photovoltaic cell or a mirror, steering material on a surface.

In some embodiments, steering material on a surface comprises moving liquid around or moving a solid object.

Claim 1:
A soft composite actuator (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>), comprising:
a strain limiting layer (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>);
a first radially constraining layer (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>); and
a first elastomeric layer (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) disposed between the first radially constraining layer (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) and the strain limiting layer (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>);
wherein
the first elastomeric layer (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>), the strain limiting layer (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>), and the first radially constraining layer (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) are bonded together to form at least one bladder (<NUM>, <NUM>) for holding pressurized fluid, and
wherein the first radially constraining layer (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) comprises one or more openings (<NUM>, <NUM>, <NUM>) through which one or more portions of the adjacent first elastomeric layer (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) expand upon actuation, and wherein the first radially constraining layer (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) comprises one or more strain limiting sections free from any openings.