Patent Publication Number: US-2022219339-A1

Title: Food handling gripper

Description:
RELATED APPLICATIONS 
     This application is a Continuation of U.S. application Ser. No. 16/148,170 filed on Oct. 1, 2018, which is a Continuation of U.S. application Ser. No. 15/194,283 filed on Jun. 27, 2016, now U.S. Pat. No. 10,112, 310, issued on Oct. 30, 2018, which claims priority to U.S. Provisional Patent Application Ser. No. 62/185,385, filed on Jun. 26, 2015 and entitled “Food Handling Gripper.” The contents of the aforementioned applications are incorporated herein by reference. 
    
    
     BACKGROUND 
     Robotic systems are employed in a number of different contexts, and may be called upon to perform a wide variety of different tasks. Robots typically manipulate objects around them using robotic manipulators such as individual actuators, grippers, or end effectors. 
     Soft robotic actuators have recently been employed in contexts in which traditional hard actuators may be inappropriate or may suffer from deficiencies. For example, in food handling, it may be advantageous to use soft robotic actuators because of their improved ability to conform to the article being grasped, thus preventing the food from becoming marred or bruised. For similar reasons, soft actuators may be used in medical settings. 
     Whether a hard robotic actuator or a soft robotic actuator is employed, the handling of certain biological or chemical materials may pose unique problems. Hard and soft robotic systems may include numerous crevices, surface roughness, indentations, fasteners, and other areas where the biological or chemical materials may accumulate and breed bacteria or spread potentially poisonous matter to other products. Traditionally, it may be difficult to remove accumulated biological or chemical materials, thus creating a contamination hazard. 
     SUMMARY 
     The present application addresses improvements in robotic systems to reduce biological or chemical harborage points on the systems. Exemplary embodiments relate to improvements in robotic actuators, grippers, hubs for connecting the actuators or grippers to a robotic arm, entire robotic systems, and other components. According to exemplary embodiments, fasteners and mounting points may be moved to internal locations on actuators and hubs, so as to present a smooth, flat surface without corners, crevices, or other points for biological or chemical materials to accumulate. Attachment points may be configured to use twist-interlock systems having rounded interlocking pieces that are easier to clean than sharp corners. Distances between adjacent components (e.g., accordion extensions on actuators) may be increased, and curves added or increased in size, to reduce harborage points. Similarly, specially-configured coverings may be employed to present a flat surface on which biological or chemical materials will exhibit reduced accumulation or which may be readily cleaned; in some embodiments, the coverings may be disposable. 
     Moreover, some embodiments provide actuators having improved designs for handling food, biological materials such as tissue, and other delicate or easily bruised or deformed materials. 
     Although exemplary embodiments are described in connection with soft robotic actuators, similar techniques may be employed with more traditional hard robotic systems. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIGS. 1A-1D  depict exemplary soft robotic actuators suitable for use with exemplary embodiments described herein. 
         FIGS. 2A-2E  depict examples of internal attachment mechanisms for affixing an actuator to a hub according to an exemplary embodiment. 
         FIGS. 3A-3E  depict examples of hub and base assemblies for affixing a robotic gripper to a robotic arm. 
         FIGS. 4A-4D  depict an example of a hub having an internal fixturing mechanism according to exemplary embodiments. 
         FIGS. 5A-5H  depict an example of a twist-lock inflation fluid supply line, according to an exemplary embodiment. 
         FIG. 6  depicts a magnetic attachment for an inflation fluid supply line, according to an exemplary embodiment. 
         FIGS. 7A-7B  depict an example of an actuator having reduced harborage points, according to an exemplary embodiment. 
         FIGS. 8A-8C  depict an accordion cover for a soft actuator, according to an exemplary embodiment. 
         FIG. 9  depicts an example of an overmolded soft gripping pad, according to an exemplary embodiment. 
         FIGS. 10A-10C  depict examples of inflatable texturing surfaces, according to exemplary embodiments. 
         FIGS. 11A-11D  depict an exemplary tapered soft actuator. 
         FIGS. 12A-12D  depict an exemplary spherically enveloping gripper. 
         FIGS. 13A-13B  depict exemplary webbing applied between actuators. 
         FIGS. 14A-14B  depict exemplary extend-and-grasp actuators. 
         FIG. 15A-15D  depict an actuator incorporating a hook, according to an exemplary embodiment. 
         FIGS. 16A-16B  depict examples of different degrees of vacuum applied to an actuator to modify the actuator&#39;s opening profile. 
         FIGS. 17-17C  depict an exemplary disposable wrapping for a robotic system. 
     
    
    
     DETAILED DESCRIPTION 
     Exemplary embodiments relate to robotic systems that are designed or configured to reduce biological or chemical harborage points on the systems. For example, in exemplary embodiments, robotic actuators, hubs, or entire robotic systems may be configured to allow crevices along joints or near fasteners to be reduced or eliminated, hard corners to be replaced with rounded edges, certain components or harborage points to be eliminated, shapes to be reconfigured to be smoother or flat, and/or or surfaces to be reconfigurable for simpler cleaning. Improved actuator designs for handling certain types of biological or chemical materials are also disclosed. 
     Exemplary embodiments may be advantageously employed in conjunction with soft robotic actuators. Soft robotic actuators are relatively non-rigid actuators that may be actuated by, for example, by filling the actuator with a fluid such as air or water. The soft actuator may be configured so that, by varying the pressure of the fluid in the actuator, the shape of the actuator changes. Accordingly, the actuator can be made to, for instance, wrap around an object. Because the soft actuator is relatively non-rigid, the actuator may better conform to the surface of the grasped object, allowing the actuator to gain a better hold on the object or more gently hold fragile objects. 
     A brief overview of soft robotic actuators and grippers will first be provided, followed by a detailed description of various aspects of exemplary embodiments. Unless otherwise noted, it is contemplated that each of the described embodiments may be used in any combination with each other. 
     Background on Soft Robotic Grippers 
     Conventional robotic grippers or actuators may be expensive and incapable of operating in certain environments where the uncertainty and variety in the weight, size and shape of the object being handled has prevented automated solutions from working in the past. The present application describes applications of novel soft robotic actuators that are adaptive, inexpensive, lightweight, customizable, and simple to use. 
     Soft robotic actuators may be formed of elastomeric materials, such as rubber, or thin walls of plastic arranged in an accordion structure that is configured to unfold, stretch, twist and/or bend under pressure, or other suitable relatively soft materials. They may be created, for example, by molding one or more pieces of the elastomeric material into a desired shape. Soft robotic actuators may include a hollow interior that can be filled with a fluid, such as air, water, or saline to pressurize, inflate, and/or actuate the actuator. Upon actuation, the shape or profile of the actuator changes. In the case of an accordion-style actuator (described in more detail below), actuation may cause the actuator to curve or straighten into a predetermined target shape. One or more intermediate target shapes between a fully unactuated shape and a fully actuated shape may be achieved by partially inflating the actuator. Alternatively or in addition, the actuator may be actuated using a vacuum to remove inflation fluid from the actuator and thereby change the degree to which the actuator bends, twists, and/or extends. 
     Actuation may also allow the actuator to exert a force on an object, such as an object being grasped or pushed. However, unlike traditional hard robotic actuators, soft actuators maintain adaptive properties when actuated such that the soft actuator can partially or fully conform to the shape of the object being grasped. They can also deflect upon collision with an object, which may be particularly relevant when picking an object off of a pile or out of a bin, since the actuator is likely to collide with neighboring objects in the pile that are not the grasp target, or the sides of the bin. Furthermore, the amount of force applied can be spread out over a larger surface area in a controlled manner because the material can easily deform. In this way, soft robotic actuators can grip objects without damaging them. 
     Moreover, soft robotic actuators allow for types of motions or combinations of motions (including bending, twisting, extending, and contracting) that can be difficult to achieve with traditional hard robotic actuators. 
       FIGS. 1A-1D  depict exemplary soft robotic actuators. More specifically,  FIG. 1A  depicts a side view of a portion of a soft robotic actuator.  FIG. 1B  depicts the portion from  FIG. 1A  from the top.  FIG. 1C  depicts a side view of a portion of the soft robotic actuator including a pump that may be manipulated by a user.  FIG. 1D  depicts an alternative embodiment for the portion depicted in  FIG. 1C . 
     An actuator may be a soft robotic actuator  100 , as depicted in  FIG. 1A , which is inflatable with an inflation fluid such as air, water, or saline. The inflation fluid may be provided via an inflation device  120  through a fluidic connection  118 . 
     The actuator  100  may be in an uninflated state in which a limited amount of inflation fluid is present in the actuator  100  at substantially the same pressure as the ambient environment. The actuator  100  may also be in a fully inflated state in which a predetermined amount of inflation fluid is present in the actuator  100  (the predetermined amount corresponding to a predetermined maximum force to be applied by the actuator  100  or a predetermined maximum pressure applied by the inflation fluid on the actuator  100 ). The actuator  100  may also be in a full vacuum state, in which all fluid is removed from the actuator  100 , or a partial vacuum state, in which some fluid is present in the actuator  100  but at a pressure that is less than the ambient pressure. Furthermore, the actuator  100  may be in a partially inflated state in which the actuator  100  contains less than the predetermined amount of inflation fluid that is present in the fully inflated state, but more than no (or very limited) inflation fluid. 
     In the inflated state, the actuator  100  may exhibit a tendency to curve around a central axis as shown in  FIG. 1A . For ease of discussion, several directions are defined herein. An axial direction passes through the central axis around which the actuator  100  curves, as shown in  FIG. 1B . A radial direction extends in a direction perpendicular to the axial direction, in the direction of the radius of the partial circle formed by the inflated actuator  100 . A circumferential direction extends along a circumference of the inflated actuator  100 . 
     In the inflated state, the actuator  100  may exert a force in the radial direction along the inner circumferential edge of the actuator  100 . For example, the inner side of the distal tip of the actuator  100  exerts a force inward, toward the central axis, which may be leveraged to allow the actuator  100  to grasp an object (potentially in conjunction with one or more additional actuators  100 ). The soft robotic actuator  100  may remain relatively conformal when inflated, due to the materials used and the general construction of the actuator  100 . 
     The actuator  100  may be made of one or more elastomeric materials that allow for a relatively soft or conformal construction. Depending on the application, the elastomeric materials may be selected from a group of food-safe, biocompatible, or medically safe, FDA-approved materials. The elastomeric materials may also be a fluoropolymer elastomer for chemical resistance. The actuator  100  may be manufactured in a Good Manufacturing Process (“GMP”)-capable facility. 
     The actuator  100  may include a base  102  that is substantially flat (although various amendments or appendages may be added to the base  102  in order to improve the actuator&#39;s gripping and/or bending capabilities). The base  102  may form a gripping surface that grasps a target object. 
     The actuator  100  may include one or more accordion extensions  104 . The accordion extensions  104  allow the actuator  100  to bend or flex when inflated, and help to define the shape of the actuator  100  when in an inflated state. The accordion extensions  104  include a series of ridges  106  and troughs  108 . The size of the accordion extensions  104  and the placement of the ridges  106  and troughs  108  can be varied to obtain different shapes or extension profiles. 
     Although the exemplary actuator of  FIGS. 1A-1D  is depicted in a “C” or oval shape when deployed, one of ordinary skill in the art will recognize that the present invention is not so limited. By changing the shape of the body of the actuator  100 , or the size, position, or configuration of the accordion extensions  104 , different sizes, shapes, and configurations may be achieved. Moreover, varying the amount of inflation fluid provided to the actuator  100  allows the actuator  100  to take on one or more intermediate sizes or shapes between the un-inflated state and the inflated state. Thus, an individual actuator  100  can be scalable in size and shape by varying inflation amount, and an actuator can be further scalable in size and shape by replacing one actuator  100  with another actuator  100  having a different size, shape, or configuration. 
     The actuator  100  extends from a proximal end  112  to a distal end  110 . The proximal end  112  connects to an interface  114 . The interface  114  allows the actuator  100  to be releasably coupled to other parts of a robotic system. The interface  114  may be made of a medically safe material, such as polyethylene, polypropylene, polycarbonate, polyetheretherketone, acrylonitrile-butadiene-styrene (“ABS”), or acetal homopolymer. The interface  114  may be releasably coupled to one or both of the actuator  100  and the flexible tubing  118 . The interface  114  may have a port for connecting to the actuator  100 . Different interfaces  114  may have different sizes, numbers, or configurations of actuator ports, in order to accommodate larger or smaller actuators, different numbers of actuators, or actuators in different configurations. 
     The actuator  100  may be inflated with an inflation fluid supplied from an inflation device  120  through a fluidic connection such as flexible tubing  118 . The interface  114  may include or may be attached to a valve  116  for allowing fluid to enter the actuator  100  but preventing the fluid from exiting the actuator (unless the valve is opened). The flexible tubing  118  may also or alternatively attach to an inflator valve  124  at the inflation device  120  for regulating the supply of inflation fluid at the location of the inflation device  120 . 
     The flexible tubing  118  may also include an actuator connection interface  122  for releasably connecting to the interface  114  at one end and the inflation device  120  at the other end. By separating the two parts of the actuator connection interface  122 , different inflation devices  120  may be connected to different interfaces  114  and/or actuators  100 . 
     The inflation fluid may be, for example, air or saline. In the case of air, the inflation device  120  may include a hand-operated bulb or bellows for supplying ambient air. In the case of saline, the inflation device  120  may include a syringe or other appropriate fluid delivery system. Alternatively or in addition, the inflation device  120  may include a compressor or pump for supplying the inflation fluid. 
     The inflation device  120  may include a fluid supply  126  for supplying an inflation fluid. For example, the fluid supply  126  may be a reservoir for storing compressed air, liquefied or compressed carbon dioxide, liquefied or compressed nitrogen or saline, or may be a vent for supplying ambient air to the flexible tubing  118 . 
     The inflation device  120  further includes a fluid delivery device  128 , such as a pump or compressor, for supplying inflation fluid from the fluid supply  126  to the actuator  100  through the flexible tubing  118 . The fluid delivery device  128  may be capable of supplying fluid to the actuator  100  or withdrawing the fluid from the actuator  100 . The fluid delivery device  128  may be powered by electricity. To supply the electricity, the inflation device  120  may include a power supply  130 , such as a battery or an interface to an electrical outlet. 
     The power supply  130  may also supply power to a control device  132 . The control device  132  may allow a user to control the inflation or deflation of the actuator, e.g. through one or more actuation buttons  134  (or alternative devices, such as a switch). The control device  132  may include a controller  136  for sending a control signal to the fluid delivery device  128  to cause the fluid delivery device  128  to supply inflation fluid to, or withdraw inflation fluid from, the actuator  100 . 
     As used herein, an actuator typically refers to a single component resembling the actuator  100 . When multiple actuators are employed together to form a gripping system that grips a target, such a system is generally referred to as a gripper (although some grippers may consist of a single actuator that grips a target in isolation). 
     Hubs and Mounting Points 
     Actuators or grippers may be mounted to a robotic arm (for example) either directly or through a separate interface such as a hub. Problematically, the connection between various components may include crevices or corners that accumulate materials and may be difficult to clean. 
     It is noted that actuators, grippers, and robotic systems may be cleaned in-place or out-of-place. In-place cleaning generally refers to cleaning some or all of a robotic system while the various parts of the system are still connected, without disassembly. For example, in-place cleaning may involve scrubbing an actuator and gripper assembly while the assembly remains mounted to a robotic arm. Out-of-place cleaning generally involves disassembling the assembly to clean the parts individually and/or access internal areas of the parts. Exemplary embodiments provide hubs and mounting locations having fewer or smaller harborage points (thus collecting less bacterial, biological, or chemical material). Moreover, exemplary embodiments are easier to clean in-place or disassemble for out-of-place cleaning, as described below. 
       FIGS. 2A-2E  depict examples of internal attachment mechanisms for affixing an actuator to a hub according to an exemplary embodiment.  FIG. 2A  depicts an internal cross-sectional view of a configuration for an attachment point for an actuator  100  that includes several harborage points. 
     The actuator  100  has a wall  202  made of an elastomeric material that surrounds an internal void  204  configured to be filled with an inflation fluid. At the proximal end of the actuator  100 , a flared section  206  is placed flush with a mounting surface  208 , which may be (for example) an interface to a gripper to be mounted on a robotic arm. A collar  210  may be snapped around the flared section  206  and secured to the mounting surface  208 . For example, the collar  210  may be fixed to the mounting surface  208  using a fastening mechanism, such as screws or bolts. An inflation fluid supply path  212  extends through the mounting surface  208 , the collar  210 , and into the void  204  to supply inflation fluid to the actuator  100 . 
     At various locations in this configuration, harborage points  214  exist where chemical or biological material may accumulate and encourage bacterial growth. For example, harborage points  214  exist at the interface between the actuator  100  and the collar  210 , where sharp corners and crevices allow biological or chemical matter to accumulate. Similarly, harborage points  214  exist at the base of the collar  210 , where the collar  210  meets the mounting surface  208 . 
     Furthermore, the actuator  100  is configured to bend when inflated, deflated, or subjected to vacuum. As the actuator  100  bends (e.g., to the left or right in  FIG. 2A ), a gap forms between the internal face of the collar  210  and the external face of the flared section  206  (and any other portion of the actuator  100  surrounded by the collar  210 ). This gap can quickly become filled with biological or chemical material and may include a number of harborage points. Moreover, this gap is difficult to access with cleaning tools while the actuator  100  is affixed to the mounting surface  208 , making in-place cleaning difficult or impossible. 
     An improved actuator configuration is depicted in  FIG. 2B . In this exemplary embodiment, the actuator  100  is secured to the mounting surface  208  using a securing mechanism  216 . The securing mechanism  216  includes a central body  218  and one or more extensions  220  extending from the central body  218 . The extensions  220  are positioned above one or more ledges  222  formed in the wall  202  of the actuator  100 , with a gap existing to allow a fastening mechanism  224  (e.g., a bolt or screw) to be inserted through the mounting surface  208  and into a corresponding hole in the body  218  of the securing mechanism  216 . When the fastening mechanism  224  is tightened, the extensions  220  are drawn into the ledges  222  and compress the elastomeric material, forming a fluid-tight gasket and a circumferential seal with the mounting surface  208  around the proximal end of the actuator  100 . Preferably, the extensions  220  extend as far as possible in order to provide increased surface area for forming the gasket. 
     The securing mechanism  216  may be made of any suitable material, such as plastic or metal. 
     As can be seen in  FIG. 2B , due to the absence of a collar the number of harborage points is reduced. In some embodiments, the portion of the flared section  206  that contacts the mounting surface  208  extends at substantially a 90° angle away from the mounting surface  208 . As a result, the force exerted by the securing mechanism  216  pushes the flared portion  206  downward, which forms a relatively strong seal with the mounting surface  208  and reduces the area of the gap between the actuator  100  and the mounting surface  208 . Thus, harborage points are reduced in the system. 
     In some cases, if bacteria should accumulate at the interface between the actuator  100  and the mounting surface  208 , the actuator  100  may be removed from the mounting surface  208  by removing the fastening mechanism  224 , and the actuator  100  may be cleaned (e.g., in a dishwasher or an autoclave, if made of suitable materials). Because the mounting surface is typically flat, it is also relatively easy to clean. 
     In some embodiments, the securing mechanism  216  may include an inflation fluid passage allowing inflation fluid to pass through the securing mechanism. The inflation fluid passage may pass through the central body  218  along with the fastening mechanism  224 , or the inflation fluid passage and the fastening mechanism may be provided on different parts of the securing mechanism  216 , as shown in the configuration depicted in  FIG. 2C . In this example, the inflation fluid passage  212  extends through the body  218  of the securing mechanism  216 . The securing mechanism  216  is provided with holes in the extensions  220  for receiving fastening mechanisms  224 . The ledges  222  in this example include a lower ledge situated below the extensions  220  and an upper ledge provided above the extensions  220 . 
     The fastening mechanisms  224  are inserted through the mounting surface  208  and through a hole in the lower ledge. The fastening mechanisms  224  then extend through the corresponding hole in the extensions  220 . In some embodiments, the fastening mechanisms  224  terminate in the extensions  220 ; in others, the fastening mechanisms  224  penetrate the extensions  220  and extend into hardware overmolded into the upper ledge. When the fastening mechanisms are tightened, the lower ledge (and the upper ledge, if the fastening mechanism extends into it) is drawn tight with the extensions  220 , creating a fluid-tight gasket. Inflation fluid is supplied to the void  204  through the inflation fluid supply passage  212 .  FIG. 2D  depicts the securing mechanism  216  of this embodiment in more detail. 
     The securing mechanism  216  may be separate from the actuator  100 , or may be integral with the actuator  100 . For example, the securing mechanism  216  may be fabricated and then overmolded into the actuator  100  at the time of actuator fabrication. 
       FIG. 2E  depicts an exemplary overmolded insert. In this case, the extensions  220  are provided between optional upper and lower ledges  222  (if the ledges  222  are not present, the securing mechanism  216  may be secured to the actuator wall  204  using, for example, surface treatments). The securing mechanism  216  receives the fastening mechanisms  224 , which pull the securing mechanism  216  towards the mounting surface  208 . Advantageously, an o-ring  226  may be provided around the outer bottom edge of the securing mechanism  216 . As the securing mechanism  216  is pulled tight against the o-ring  226 , the o-ring  226  provides a strong seal, reducing the gap between the securing mechanism  216  and the mounting surface  208 . 
     Furthermore, because of the shape of the relatively hard (as compared to the o-ring  226 ) securing mechanism  216 , the securing mechanism  216  provides a hard stop for the fastening mechanism  224 . For example, the o-ring  226  may be silicon or an elastomer such as a flouropolymer elastomer, whereas the securing mechanism  216  may be food-safe plastic (e.g., PETE, delrin, polyethelene, or polypropylene) or metal (e.g., stainless steel with a grade of  303 ,  304 , or  316 , or hard anodized aluminum). Because of the relatively hard or rigid nature of the securing mechanism  216 , there comes a point during the tightening of the fastening mechanisms  224  when the securing mechanism  216  cannot be drawn further towards the mounting surface  208 . This prevents the o-ring  226  from becoming over- or under-compressed and allows the securing mechanism  216  to be tuned (by varying the shape of the securing mechanism  216 , particularly the size and configuration of the gap which seats the o-ring  226 ) to put a predetermined amount of force on the o-ring  226 . 
     Traditionally, external screws or bolts are used to fix an actuator or actuator assembly to a mounting surface  208 . These external fastening mechanisms create harborage points; the embodiments of  FIGS. 2A-2E  eliminate the external fastening mechanisms and replace them with internal fastening mechanisms to thereby reduce or eliminate these harborage points. Moreover, the interface between the actuator  100  and the mounting surface  208  may be held tight by the application of the fastening mechanisms  224 , reducing the gap between the actuator  100  and the mounting surface  208  and thereby reducing harborage points. 
       FIGS. 3A-3E  depict further examples of hub and base assemblies for affixing a robotic gripper to a robotic arm without using external fastening mechanisms like bolts or screws. These assemblies may be used in conjunction with, or as an alternative to, the assemblies of  FIGS. 2A-2D . 
       FIGS. 3A-3C  depict the “twist-to-lock” nature of the hub/base assembly. The assembly includes one or more actuators  100  mounted into an actuator holder  304 , which may be formed of any suitable material such as plastic or metal. An overmolded elastomer layer  302  holds the actuators  100  on the actuator holder  304  and covers crevices, corners, and other features of the actuators  100  that could serve as harborage points. For example, as shown in  FIG. 3E , the overmolded elastomer layer  302  may cover the proximal end of the actuator  100  up to the ridge on the most-proximal accordion extension. A gripper base  306  includes an inflation fluid chamber  310  for distributing inflation fluid to the actuators  100 . The gripper base  306  may be affixed or may be affixable to a robotic arm. 
     The actuator holder  304  is provided with one or more grooves  312  configured to mate with, and interlock with, corresponding extensions  314  on the gripper base  306 . As shown in  FIGS. 3B and 3C , the gripper assembly including the actuators  100 , the overmolded elastomer layer  302 , and the actuator holder  304  may be placed over the gripper base  306  and twisted to mate the extensions  314  into the grooves  312 . It should be noted that the interlocking mechanism may be reversed (e.g., with grooves  312  on the gripper base  306  and extensions  314  on the actuator holder  304 ). 
     The use of an interlocking system allows for a screwless assembly, thereby removing potential harborage points. Moreover, this configuration allows the actuator holder  304  (along with the actuators  100  and the overmolded elastomer layer  302 ) to be easily removed from the base  306  so that the base  306  may be easily cleaned out-of-place (i.e., when the base  306  has been removed from the robotic assembly). 
       FIG. 3D  shows a close up exterior view of the assembled gripper system. As shown in  FIG. 3D , the interface  308  at which the gripper base  306  mates to the actuator holder  304  includes smooth, curved surfaces. Thus, both the gripper base  306  and the actuator holder  304  do not require sharp corners at the interface  308 , which reduces harborage points and allows for simpler cleaning. Moreover, surfaces that may come into contact with chemical or biological material may have a smoothness value of at least 1 microinch, more preferably at least 16 microinches, and more preferably at least 32 microinches. 
     In general, throughout the application, and particularly in the case of internal angles, the angle between two surfaces may be at least 135°. By making these internal angles relatively open, it is easier to clean these internal surfaces (e.g., with a brush or other tool). Similarly, when a curve is used, such as in the case of the interface  308 , the radius of the curve may be at least 1/32″, or more preferably ⅛″, or more preferably ¼″, depending on the application. 
       FIG. 3E  shows an internal view of the various components of the gripper system. An inflation fluid chamber  310  is provided in the gripper base  306  for supplying inflation fluid to the actuators  100 . An inflation fluid supply line  212  extends through the actuator holder  304 , through the overmolded elastomer  302 , and into the void  204  of the actuator  100 . Multiple inflation fluid supply lines  212  may be provided (e.g., one for each actuator  100  in the gripper assembly). The inflation fluid supply line  212  may be configured to mate with a corresponding interface on the inflation fluid chamber  310 , or may simply extend to a large opening on the inflation fluid chamber  310 . Because most of the opening of the chamber  310  will be covered by the actuator holder  304 , the only place for inflation fluid to escape will be into the inflation fluid supply lines  212  and into the actuators  100 . 
     As shown in  FIG. 3E , the lower walls  316  inflation fluid chamber  310  have a curved shape and relatively wide openings. Moreover, the internal surfaces of the inflation fluid chamber  310  are relatively smooth (e.g., having a smoothness value of 32 microinches or more. These features reduce harborage points, allows cleaning fluid to drain out of the base after cleaning, more readily allows access by cleaning tools such as brushes, and provide for easier visual inspection to ensure that the inflation fluid chamber  310  has been sufficiently cleaned. 
       FIGS. 4A-4D  depict a further example of a hub according to exemplary embodiments. 
       FIGS. 4A and 4B  depict a hub having an external fixturing mechanism  224 . As shown in  FIG. 4A , a number of actuators  100  are secured together to form a gripper. The actuators  100  are inserted into a plate  402 , and the plate  402  is affixed to a robotic base  404  (e.g., a robotic arm or another structure to be fixed to a robotic arm). The plate  402  is secured to the robotic base  404  using a fixturing mechanism  224  (e.g., a screw or bolt), as shown in the closeup in  FIG. 4B . The protruding fixturing mechanism  224  provides a number of harborage points for the gripper system. 
     In contrast,  FIG. 4C  depicts a perspective view of a hub having an internal fixturing mechanism. As can be seen in this example, the plate  402  presents a flat surface with no external screws. As shown in the cross-sectional view of  FIG. 4D , an internal fixturing mechanism  224  is routed through an inflation fluid supply path  212 , and secures the plate  402  from the bottom. 
     Using the above-described hub assemblies (individually or in any combination), harborage points can be reduced or eliminated from the interconnections between the actuators/actuator holders and other parts of the system. Other harborage points may exist elsewhere, however. For example, inflation fluid may be supplied to a hub or other part of the system through an inflation fluid supply line such as a pneumatic fitting.  FIGS. 5A-5H  depict an example of a twist-lock inflation fluid supply line for reducing harborage points, according to an exemplary embodiment. 
       FIG. 5A  provides a perspective view of a gripper including four actuators  100  connected to an actuator holder  502 . The actuator holder  502  may be mounted to a robotic arm. 
     As shown in the close-up of  FIG. 5B , the actuator holder  502  includes a port  504  for receiving a fitting  506  for an inflation fluid supply line. The port  504  is configured to interconnect with the fitting  506  through a twist interlock system. In this example, the port  504  includes one or more fingers  508  that mate to one or more filleted slots  510  on the fitting  506 . The filleted slots  510  may be relatively wide or thick to allow for easy cleaning (thus more easily receiving a brush or other cleaning device as compared, for example, to screw threads). The internal bend  509  in the fingers  508  may have a curved or teardrop cross-sectional profile, with a curve radius of at least 1/32″, or more preferably 1/16″, or more preferably ¼″, in order to grip the filleted slots  510  while also remaining relatively easy to clean (as e.g., enabling easier access with a cleaning tools such as a brush). 
     One or more grooves  512  in the fitting  506 , each groove corresponding to a finger  508 , provide clearance allow the fitting  506  to be pushed onto the port  504  between the fingers  508 , as shown in  FIG. 5C . 
     Once inserted onto the port  504 , the fitting  506  may be twisted to lock the fitting  506  into place, as shown in  FIG. 5D . In an exemplary embodiment, the fitting  506  may be twisted about 120° to allow for relatively simple assembly, although other degrees of twist (e.g., 90° or 30°) are also possible. In order to accommodate this amount of twisting, the grooves  510  may be shaped and configured to allow for a 120° twist. Moreover, the grooves  510  may be shaped with an upward curve so that, as the fitting  506  is twisted, the fitting  506  undergoes linear displacement towards the hub  502 , thus pressing the fitting  506  into place against the hub and creating a fluid-tight seal. 
       FIGS. 5E-5H  depict the twisting action in more detail.  FIG. 5E  depicts an external view of an unlocked fitting  506  from the front, while  FIG. 5H  depicts an internal cross-sectional view of the unlocked fitting  506  from the side. Note that, in the unlocked configuration, a gap  514  exists between the bottom of the fitting  506  and the hub  502 . 
       FIG. 5G  depicts an external view of a locked port  504  (after twisting the port  504  to lock it in place) from the front, while  FIG. 5H  is an internal view of the locked port  504  from the side. By comparing  FIG. 5F  to  FIG. 5H , it can be seen that twisting the port  504  results in an amount of linear displacement d which brings the bottom of the port  504  into contact with the hub  502 . 
     Alternatively or in addition, magnets may be used to secure an inflation fluid supply line to a hub.  FIG. 6  depicts a magnetic attachment for an inflation fluid supply line, according to an exemplary embodiment. In this example, a hub  602  supports two actuators  100 . The hub  602  is provided with a first annular magnet  606  surrounding an inflation fluid supply path  212 . An inflation fluid supply line  610  for providing inflation fluid to the hub  602  includes a fitting  608  that incorporates a second annular magnet  604 . The first annular magnet  606  and the second annular magnet  604  may have opposite polarities so that, when brought into close proximity with one another, the first annular magnet  606  mates with the second annular magnet  604  and forms a fluid-tight seal. Because the magnets  604 ,  606  are annular, inflation fluid flows through the hole in the magnets  604 ,  606  and into the hub  602 , from which it can be distributed to the actuators  100 . 
     Next, innovations in actuator design and application for handling biological or chemical materials is discussed. 
     Actuator Design and Application 
       FIGS. 7A-7B  depict an example of an actuator having reduced harborage points, according to an exemplary embodiment.  FIG. 7A  depicts a first actuator  700 , in which the ridges  106  of adjacent accordion extensions  104  are separated by relatively large distances r, and the troughs  108  are relatively deep (represented by the distance t). Both the ridges  106  and the troughs  108  have relatively sharp curves or sharp corners. Particularly in the case of the troughs  108 , which have interior angles into which it may be difficult to place a brush or cleaning mechanism, these curves and corners create a number of harborage points  702 . 
       FIG. 7B  depicts a modified actuator  704 . In this example, the ridges  106  of adjacent accordion extensions are further apart (separated by a relatively larger distance r′), while the troughs  108  are more shallow (represented by the distance t′, which is less than t). The ridges  106  and the troughs  108  have more rounded edges, with gentler curves. 
     As a result, edges on the actuator  704  are smoothed, reducing bacterial harborage points. Moreover, clearings on the actuator  704  are expanded, which makes it easier to clean the actuator  704  with a brush, pad, solution, etc. to remove bacteria and food debris from the actuator  704 . 
     To further reduce harborage points, the accordion extensions  104  may be covered entirely so that the non-gripping side of the actuator presents a smooth or flat surface.  FIGS. 8A-8C  depict an accordion cover for a soft actuator, according to an exemplary embodiment. 
       FIG. 8A  depicts an actuator  100  having a plurality of accordion extensions  104 . A most-proximal accordion extension includes a starting ridge  802 , and a most-distal accordion extension includes an ending ridge  804 . 
     To eliminate or reduce harborage points between or on the accordion extensions  104 , the accordion extensions  104  may be covered with an accordion cover  806 , as shown in  FIG. 8B . The accordion cover  806  may be formed of a highly extensible elastomer configured to readily flex when the actuator  100  is inflated with inflation fluid or subjected to a vacuum. Thus, the accordion cover  806  does not hinder the expansion or contraction of the actuator  100 . 
     The accordion cover  806  may be removable, or may be integrated with the actuator  100 . For example, the accordion cover  806  may be an elastomer that fully encases the accordion extensions  104  and fills in the areas between the accordion extensions  104 . 
     As shown in the internal cross-sectional view of  FIG. 8C , the accordion cover  806  may extend from the starting ridge  802  to the ending ridge  804 . In other embodiments, the accordion cover  806  may extend beyond the starting ridge  802  and/or the ending ridge  804 . Alternatively or in addition, the accordion cover  806  may cover some, but not all, of the accordion extensions  104 . 
     The gripping surface of the actuator  100  may also be supplemented. For example,  FIG. 9  depicts an example of an overmolded soft gripping pad  902 , according to an exemplary embodiment. The soft gripping pad  902  is provided on at least a portion of the gripping surface of the actuator  100 . The soft gripping pad  902  may be integral with the actuator  100 , or may be a separate part that is affixed to the actuator  100  (e.g., using elastomeric bands), allowing the pad  902  to be removed for separate cleaning. 
     The soft gripping pad  902  may be formed of a soft elastomeric material (e.g., an elastomeric material that is relatively more flexible, pliable, or yielding to a force than the elastomeric material from which the actuator  100  is formed) and may allow the actuator  100  to manipulate delicate objects, such as tomatoes, without bruising the objects&#39; surface. 
     An interface  904  between the gripping pad  902  and the base  102  of the actuator  100  is curved to reduce or eliminate a potential harborage point. 
     In further embodiments, the gripping surface of the actuator  100  may be provided with other types of texturing that are readily cleaned. For example,  FIGS. 10A-10C  depict cross-sectional side views of actuators having inflatable texturing surfaces, according to exemplary embodiments. 
       FIG. 10A  depicts an actuator  100  in an uninflated state. The actuator  100  includes a wall  202  surrounding a void  204  into which inflation fluid may be supplied. On the base  102  of the actuator, the thickness of the wall  202  varies between alternating thick-walled portions  1002  and thin-walled portions  1004 . The thin-walled portions  1004  have a thickness that is relatively smaller than the thick-walled portions  1002 . 
     In the uninflated state, the base  102  of the actuator  100  is flat. Thus, when not inflated, the actuator exhibits fewer or no harborage points on the base  102  that forms the gripping surface, and can be readily cleaned. 
     However, when inflated (as shown in  FIG. 10B ), the inflation fluid enters the void  204  and presses against the external walls  202  of the actuator. Because the thin-walled portions  1004  are less rigid or resistant to inflation than the thick-walled portions  1002 , the thin-walled portions  1004  may bow out, creating a textured base  102 . Thus, the actuator  100  may more readily grip an object. When the inflation fluid is removed, the thin-walled portions  1004  return to their flat configuration and the base  102  becomes smooth again, for easy cleaning. 
     Note that  FIG. 10B  depicts the base  102  in a textured configuration (implying the presence of inflation fluid in the void  204 ), although the actuator  100  is in an unbent configuration. In real-world scenarios, applying inflation fluid would typically cause the actuator  100  to bend, as shown in  FIG. 1A ; the bending is not shown in  FIG. 10B  for ease of understanding. 
     Instead of the thin-walled portions  1004  and the thick-walled portions  1002 , the base  102  may be formed of alternating materials of different types that are more or less resistant to expansion upon inflation. When inflated, the portions of the base  102  with less resistant materials will expand more than the portions of the base  102  with more resistant materials, creating a textured surface. 
     Moreover, a similar effect may be achieved by applying a vacuum instead of inflation fluid. For example, the thin-walled portions  1004  may be configured to be in an extended configuration by default. Upon application of a vacuum, the thin-walled portions  1004  may bow inwards, creating a flat surface. 
       FIG. 10C  depicts an alternate configuration in which the texturing of the base may be applied independently of inflation of the actuator  100 . In this example, an internal wall  1006  separates the void  204  into two chambers. A first chamber  1008  exists in the area adjacent to the base  102 , while a second chamber  1010  fills the remainder of the actuator  100 . The two chambers  1008 ,  1010  may be inflated independently of one another. When the first chamber  1008  is filled, the thin-walled portions  1004  bow outwards, creating a textured surface on the base  102 . When the second chamber  1010  is filled, the actuator  100  bends according to its inflation profile in order to grasp a target. 
     In addition to providing systems that reduce harborage points, it may also be useful when working with biological or chemical materials to use special purpose actuators well-suited to contexts in which these materials are often handled. 
     For example,  FIGS. 11A-11D  depict an exemplary tapered soft actuator  1100 .  FIG. 11A  depicts a perspective view of the tapered actuator  1100 , while  FIGS. 11B, 11C, and 11D  depict side, front, and bottom views, respectively. As shown in these Figures, the actuator  1100  tapers both in thickness (t) and in breadth (b) from the proximal end  112  to the distal end  110 . 
     It is noted that the tapered actuator  1100  need not necessarily taper uniformly across or along the actuator  1100 . For example, different effects may be achieved by utilizing different relative degrees of taper along the width, length, or wall thickness of the actuator, or by tapering the amplitude of respective accordions, resulting in an alteration of lateral actuator stability, axial finger stability, gradient changes in expansion when actuated, or gradient changes in curvature response when actuated, respectively. 
     A tapered actuator  1100  is exceptionally stable in torsion, has a large surface area for friction-dominated grasp, maintains small and dexterous finger tips for manipulation of small items, and delivers relatively higher grasping force per the same pressure as compared to an actuator having a homogeneous cross-section. This allows tapered actuators  1100  to be deployed in tandem with each other, for example in a circular or rectangular pattern, for precision handling of a range of object sizes and weights. Moreover, tapered actuators  1100  are particularly well-suited to manipulating wet, slippery, oddly/irregularly shaped, and cluttered food items (e.g., food items in a heap or in form fitting packaging). 
     Moreover, a tapered actuator  1100  may be better able to navigate cluttered environments as compared to a non-tapered actuator (e.g., bushels of unstructured fruit or produce). 
     For example,  FIGS. 12A-12D  depict an exemplary spherically enveloping gripper employing skewed actuators  1200 . These leaf-shaped skewed actuators  1200  are well-suited to fully enclosing fragile objects.  FIG. 12A  depicts a perspective view of a gripper employing four skewed actuators  1200 , whereas  FIGS. 12B, 12C, and 12D  depict front, side, and bottom views of the a single actuator  1200 , respectively. 
     As can be seen in  FIG. 12D  (bottom view), the skewed actuator  1200  includes a plurality of skewed internal chambers  1202  for receiving inflation fluid. The skewed chambers  1202  have a teardrop or other skewed shape that expands from a relatively narrow region r 1  to a relatively wider region r 2 . The relatively narrow r 1  region may be disposed close to the center of the skewed actuator  1200  (e.g., the portion of the internal chamber  1202  that is closest to the centerline A-A, as shown in  FIG. 12B ), whereas the relatively wider region r 2  be disposed towards the external edge of the skewed actuator  1200 , away from the centerline A-A. 
     The skewed actuators  1200  have a number of characteristics. 
     First, each skewed actuator  1200  has multiple degrees of freedom when actuated. In other words, the skewed actuators  1200  bend about its major axis (e.g., around the central axis to curve in the circumferential direction as depicted in  FIGS. 1A and 1B ) as well as across its minor axis (in the axial direction of  FIGS. 1A and 1B ). 
     Second, the skewed actuator  1200  has a relatively broad leaf-like shape which tends to form a completely enclosing sphere when matched with other tapered actuators  1200  in a circularly- or rectangularly-patterned layout. 
     Third, the tapered design of the skewed actuator  1200  improves stability and increases grasping force. These properties make such an actuator well-suited to manipulating, for example, many types of roughly round fruits and vegetables. Because the skewed actuator  1200  encompasses an object (referred to herein as providing a “caging” grip), the skewed actuator  1200  may allow the skewed actuator  1200  to, for example, pick delicate fruit from a tree (e.g., apples) or vine (e.g., tomatoes or grapes). A task such as fruit picking may require a stronger grip than, for example, simply moving picked fruit from one location to another. Because a stronger grip is required, if the grip is focused in a few locations (e.g., at the fingertips of the actuators), then the fruit can be bruised or damaged. By applying a caging grip, this force may be distributed over a larger surface area, which improves the chances of picking the fruit without bruising it. 
     Objects may be fully encompassed or encapsulated by other methods as well. For example,  FIGS. 13A-13B  depict webbing  1302  applied between actuators  100  in order to allow the actuators  100  to fully encapsulate objects. The webbing  1302  may be formed of relatively extensible elastomeric material to allow the webbing to expand while the actuators  100  are in an open state ( FIG. 13A ), while maintaining a reasonable amount of tension when the actuators  100  are in a closed state ( FIG. 13B ), so as to maintain the grasped object within the webbing  1302 . The use of webbing  1302  allows for increased surface area contact between a gripper and an object. 
     In some cases, an object to be grasped may be located deep within a container, such as a bin, where the object may be difficult to reach.  FIGS. 14A-14B  depict exemplary extend-and-grasp actuators suitable for these and other applications. 
       FIG. 14A  depicts an inflated extensible actuator  1400 , while  FIG. 14B  depicts an uninflated extensible actuator  1400 . The extensible actuator  1400  includes a number of accordion extensions  104  divided into two sections. A full accordion section  1402  includes accordion extensions  104  that extend around a full diameter of the extensible actuator  1400 . A partial accordion section  1404  includes accordion extensions  104  that extend only part way around the diameter of the extensible actuator  1400 . The full accordion section  1402  may include accordion extensions  104  at a higher frequency or rate than the partial accordion section  1404 . 
     As a result, when the extensible actuator  1400  is inflated, at a relatively low inflation pressure the full accordion section  1402  begins to extend (under a relatively small amount of force). This causes the extensible actuator  1400  to extend linearly, with a relatively small degree of curvature at the distal end, which allows the extensible actuator  1400  to (for example) reach into a bin or container that might otherwise be blocked by the actuator&#39;s hub assembly  1406 . At relatively high inflation pressure, the partial accordion section  1404  exhibits increasing degrees of curvature, allowing the extended actuator to grasp an object. 
     In further embodiments, an actuator may employ a special geometry in order to better grasp particular targets. For example,  FIG. 15A-15D  depict an actuator incorporating a hook, according to an exemplary embodiment. 
     As shown in  FIG. 15A , the hooked actuator  1500  includes a curved protrusion  1502  at its distal end in the shape of a hook. Accordingly, when the hooked actuator  1500  is inflated in order to grasp an object ( FIGS. 15B, 15C, and 15D , showing varying degrees of inflation pressure), the curved protrusion  1502  of the hooked actuator  1500  extends underneath the object to be grasped ( FIG. 15C ), subsequently pulling the object inward ( FIG. 15D ). This allows for greater contact with the gripping surface of the hooked actuator  1500 , and improves the stability of the object while it is being moved or manipulated. 
     Regardless of the type of actuator used, it may be helpful in some scenarios to increase the opening between actuators prior to grasping a target. For example, when grasping a large object, a relatively large opening angle may be called for. When grasping a small object, a relatively small opening angle may be called for. 
     To achieve different degrees of opening, vacuum may be applied to the actuator (e.g., instead of filling the actuator with an inflation fluid, ambient fluid in the actuator may be removed from the actuator). For instance,  FIGS. 16A-16B  depict examples of different degrees of vacuum applied to actuators  100  to modify the actuators&#39; opening profile.  FIG. 16A  depicts a relatively large opening angle achieved by applying a relatively large amount of vacuum to the actuators  100 .  FIG. 16B  depicts a relatively small opening angle achieved by applying a relatively smaller (or no) amount of vacuum. 
     In some embodiments, a robotic system is configured to provide a precise, predetermined amount of vacuum to one or more actuators  100 . The predetermined amount may be selected in an amount that accommodates the environment in which the actuator  100  is intended to operate and the size or configuration of the object that the actuator  100  is intended to grasp. For example, if too little vacuum is applied, the actuator  100  will not open sufficiently to grasp the target. On the other hand, if too much vacuum is applied, the actuator  100  will open more widely than is necessary, which may cause the actuator  100  to collide with the container holding the target object and/or other objects near the target object. This is especially true in cluttered environments. By providing a predetermined amount of vacuum, the actuator  100  can be opened enough to allow the target object to be grasped while still providing sufficient space between the actuator and adjacent objects or containers. 
     Robotic System Covering 
     In a further embodiment, the system may be made easier to clean by applying a food-safe or medically-safe wrapping around some or all of a robotic system. For example,  FIGS. 17A-17C  depict an exemplary disposable wrapping for a robotic system  1700 . 
     As shown in  FIG. 17A , the robotic system  1700  includes a robotic arm  1702  to which a hub  1704  is mounted. Actuators  100  are connected to the hub  1704 . A disposable wrapping  1706 , which is sized and shaped to correspond to the robotic system  1700 , is provided around the robotic system  1700 . 
     The disposable wrapping  1706  is sized and shaped to be relatively loose when the actuators  100  are in an uninflated state ( FIG. 17B ) and relatively tighter (without risking breakage of the disposable wrapping  1706 ) when the actuators  100  are in an inflated state ( FIG. 17C ). For example, the size and shape of the bag may be selected so as to provide a predetermined amount of slack when the actuators  100  are uninflated. When the actuators  100  are inflated, the slack is reduced and the actuators  100  may grip a target object. Alternatively or in addition, the disposable wrapping  1706  may be formed of elastic materials in order to allow the disposable wrapping  1706  to compensate for inflation of the actuators  100 . 
     It is noted that the wrapping  1706  need not necessarily be disposable. In some embodiments, the wrapping  1706  may be capable of removal for cleaning, and may be re-used once cleaned. 
     Using the above-described embodiments, individually or in combination with each other, biological and chemical materials may be more readily handled by robotic systems. The described embodiments reduce biological/chemical/bacterial harborage points, allow for easy cleaning, and improve the grasping and reaching capabilities of grippers, among other advantages.