Patent Publication Number: US-2023139968-A1

Title: Robot end effector

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application 63/274,136, filed Nov. 1, 2021, which is incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The embodiments described herein generally relate to robot end effectors and, more particularly, robot end effectors that include deformable grippers that are movable such that an angle greater than or equal to these grippers define an angle between the deformable grippers that is equal to or greater than 130 degrees. 
     BACKGROUND 
     Conventional robots include object grasping and manipulating members that are utilized to interact with and grasp different types of objects in a domestic environment. For example, these robots may help elderly and physically disabled people perform various tasks in their homes such as, e.g., pick up, move, and place objects in various locations within their homes. These robots suffer, however, from numerous deficiencies. In particular, these robots lack object grasping and manipulating members that are capable of grasping and moving objects of varying sizes and dimensions, namely objects having dimensions that are larger than the dimensions of the robots. Additionally, the grasping and manipulating members may not possess the ability to rotate objects around a pivot that is located as part of or on the manipulating members. The manipulating members of conventional robots may also lack friction based contact surfaces operating in conjunction with certain mechanical components that serve as environmental constraints for ensuring that objects that are picked up do not slip from the grasp of the manipulating members. It is further noted that conventional robots may lacking pressure sensing capabilities and depth cameras such as, e.g., a time-of-flight camera. 
     Accordingly, a need exists for robots having grasping members that enable these robots to firmly grasp and move objects of varying dimensions, including objects that are disproportionately larger than the robots, from one location to another while ensuring that these objects do not slip and fall. 
     SUMMARY 
     In one embodiment, a robot end effector is provided. The robot end effector comprises a first deformable gripper, a second deformable gripper coupled to the first deformable gripper by a linkage, and an actuator coupled to the linkage and operable to move at least one of the first deformable gripper and the second deformable gripper to a position defining an angle between the first deformable gripper and the second deformable gripper that is greater than or equal to 130 degrees. 
     In another embodiment, another robot end effector is provided. The robot end effector comprises a first deformable gripper, a second deformable gripper coupled to the first deformable gripper by a linkage, and an actuator coupled to the linkage and operable to move at least one of the first deformable gripper and the second deformable gripper to: a fully open defining an angle between the first deformable gripper and the second deformable gripper that is greater than or equal to 130 degrees, and a half open position defining an additional angle between the first deformable gripper and the second deformable gripper that is approximately 90 degrees. 
     These and additional features provided by the embodiments described herein will be more fully understood in view of the following detailed description, in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiments set forth in the drawings are illustrative and exemplary in nature and not intended to limit the subject matter defined by the claims. The following detailed description of the illustrative embodiments can be understood when read in conjunction with the following drawings, where like structure is indicated with like reference numerals and in which: 
         FIG.  1    depicts an example implementation of a robot end effector according to one or more embodiments described and illustrated herein; 
         FIG.  2    depicts a detailed illustration of various parts of the linkage of the robot end effector, according to one or more embodiments described and illustrated herein; 
         FIG.  3 A  depicts an example implementation of the robot end effector in which the first deformable gripper and the second deformable gripper of the effector are positioned at various acute angles, according to one or more embodiments described and illustrated herein; 
         FIG.  3 B  depicts an example implementation of the robot end effector in which the first deformable gripper and the second deformable gripper are positioned at a ninety degree angle and an obtuse angle, according to one or more embodiments described and illustrated herein; 
         FIG.  4    depicts a plurality of example orientations of the robot end effector in which the first deformable gripper and the second deformable gripper interact with, grasp, and are configured to manipulate various objects having dimensions that significantly larger than the dimensions of the deformable grippers, according to one or more embodiments described and illustrated herein. 
         FIG.  5    depicts the robot end effector grasping and partially rotating an example external object, according to one or more embodiments described and illustrated herein; and 
         FIG.  6    depicts a non-limiting example of a controller that is configured to perform one or more of the features and functionalities described in the present disclosure, according to one or more embodiments described and illustrated herein. 
     
    
    
     DETAILED DESCRIPTION 
     As stated above, conventional robots may include object grasping and object manipulating members that are utilized to move objects within an environment, e.g., an apartment, a home, etc. However, these members may suffer from numerous deficiencies, namely the inability to grasp and move objects having dimensions that are larger than the dimensions of the robots themselves. Conventional robots may also lack contact surfaces having a significant amount of friction, in particular, friction that enables these surfaces to maintain a grasp on objects that is strong enough to prevent these objects from slipping and falling. Additionally, as stated, the grasping and manipulating members of these robots may not have the ability to rotate objects around a pivot, e.g., a rotational movement that is similar to the movement of a wrist. 
     The robot end effectors as described in the present disclosure address and overcome these deficiencies. In particular, the robot end effectors of the present disclosure includes deformable grippers that may be moved relative to each other such that an angle that is equal to or greater than one hundred and thirty degrees may be formed between the deformable grippers. Additionally, each of the deformable grippers include a base member and a deformable member having a contact surface formed of latex, which provides friction that enables the deformable grippers to firmly grasp various objects and maintain the grasp on these objects such that these objects do not slip. Configuring the robot end effector at an angle that is greater than ninety degrees when combined with a latex surface of the gripper, enables the robot end effector to firmly grasp objects, including those having dimensions that are larger than the dimensions of the robot end effector. It is further noted that robot end effector may include pressure sensors that calculate pressure data exerted at the point of contact with various external objects, which may be utilized to ensure that the pressure exerted by the deformable grippers does not bend, break, or otherwise damage the external objects contacting the deformable grippers. 
     It is also noted that that deformable member that is comprised of latex (or another comparable material) may have a degree of compressibility or softness that makes the robot end effector conducive for interaction directly with humans or with various objects in or near the presence of humans. In embodiments, the robot end effector of the present disclosure may also include an active pressure control feature that enables the robot end effector to traverse areas within a domestic environment that are particularly cluttered and pick up and manipulate items with a higher degree of precision as compared to conventional robots. 
     These deformable grippers may also be configured to perform a rotation action while grasping external objects such that the rotation action is similar to a wrist action performed by a human being. Such a rotational action may enable the deformable grippers to access gaps between walls in a domestic environment, areas around corners, and other such locations where a robot may not be able to travel and access. 
       FIG.  1    depicts an example implementation of a robot end effector as described in the present disclosure. In particular,  FIG.  1    depicts the robot end effector  102 , which may include a controller  114  (e.g., a computing device) and an actuator  109 . The actuator  109  may be a motor such as, e.g., a Dynamixel XM540-W270-R motor. The controller  114  may provide instructions to the actuator  109 , based on which the actuator  109  may operate to move the first deformable gripper  104  relative to a second deformable gripper  106  to various positions such that an angle defined between the first deformable gripper  104  and the second deformable gripper  106  may range from approximately 133 degrees to 1 degree. It is noted that the second deformable gripper  106  may be coupled to the first deformable gripper  104  by a linkage, which is illustrated in  FIG.  2    and described in greater detail later on in this disclosure. 
     It is noted that deformability of the first deformable gripper  104  and the second deformable gripper  106  may refer, for example, to ease of deformation of deformable portions of the robotic system, e.g., ease of deformation of deformable sensors. Deformability may also refer to how easily a portion of the robot end effector contracts when contacting an object. A deformable sensor may be positioned within each of the deformable grippers and may be a camera or comparable sensor that is capable of high spatial resolution. The deformable sensor positioned within each of the deformable grippers may be a dense tensile sensing sensor that provides the robot with a fine sense of touch, e.g., comparable to the touch associated with a human&#39;s fingers. The deformable sensor may also have a depth resolution for measuring movement towards and away from the sensor. 
     In embodiments, each of the first deformable gripper  104  and the second deformable gripper  106  may comprise two distinct components—a base member and a deformable member. In embodiments, both of the first deformable gripper  104  and the second deformable gripper  106  may be connected to pneumatic tubes that are disposed within various parts of the robot end effector  102 . These tubes may be configured to detect changes in pressure values of the first deformable gripper  104  and the second deformable gripper  106  based on various objects contacting the deformable members of these deformable grippers. A plurality of pressure sensors may be disposed within the first deformable gripper  104  and the second deformable gripper  106 . As a non-limiting example, these sensors may be configured to measure pressure values ranging from, e.g., 0 to 172.37 kPa. Additionally, each of the deformable members of the first deformable gripper  104  and the second deformable gripper  106  can also geometry or pose of an object that contacts the sensor. 
     In embodiments, as a non-limiting example, the base member of the first deformable gripper  104  and the second deformable gripper  106  may be formed of acrylic and the deformable member of the grippers may be comprised of latex. In embodiments, the surface of the deformable members in each of the first deformable gripper  104  and the second deformable gripper  106  may be embedded with a pattern. Additionally, in embodiments, the deformable member may be attached or adhered to the base member and a depth camera may be disposed or positioned on the surface of the base member such that the depth camera is positioned to capture images of one or more external objects that contact the outer surface of the deformable member. It is noted that each of the first deformable gripper  104  and the second deformable gripper  106  may include a depth camera. In embodiments, the depth cameras, upon receiving instructions from the controller  114 , may capture images, in real time, of one or more external objects that contact the outer surfaces of the these members. These images may also be utilized by the controller  114 , individually or in combination with one or more computing devices external to the robot end effector  102 , to determine the precise location on the outer surfaces of the deformable grippers on which the external objects contact, which may help reduce the instances of these objects slipping from the grasp of the deformable grippers. 
     In particular, in embodiments, upon external objects contacting the outer surfaces of the deformable surface members, the depth cameras of each of these grippers may capture images of the interior portions of the deformable surface members. In particular, the depth cameras may capture images of deformations of the deformable surface members based on contact from the external objects. These deformations correspond to changes in depth levels of the surface members, which may be detectable in the images captured by the depth cameras. Additionally, these images may also illustrate or indicate changes in depth levels associated with the patterns. Based on the changes in depth levels and the changes in the patterns, the controller  114 , operating independently or in combination with one or more external computing devices, may determine various characteristics specific to the external objects, e.g., a geometric shape of these external objects, a position or orientation of these external objects relative to the first deformable gripper  104  and the second deformable gripper  106 , and so forth. 
     In embodiments, as stated above, the first deformable gripper  104  and the second deformable gripper  106  may be oriented in a plurality of positions—a fully-open position  108 , a half-open position  110 , a closed position  112 . In embodiments, the fully-open position  108  defines an angle between the first deformable gripper  104  and the second deformable gripper  106  that is approximately 133 degrees, while the half-open position  110  defines an angle between the first deformable gripper  104  and the second deformable gripper  106  that is approximately 90 degrees. It is noted, however, that the angle defining the fully open position may vary in that the angle may higher or lower than 133 degrees. A variety or other angle values are also contemplated. 
     The closed position  112  corresponds to an angle between the first deformable gripper  104  and the second deformable gripper  106  that is approximately 2-10 degrees. In embodiments, the actuator  109  may be provided with instructions from the controller  114  such that the actuator  109  may operate to move the first deformable gripper  104  relative to the second deformable gripper  106 , e.g., at any angle between approximately 0 degrees to 130 degrees. In embodiments, it is noted that actuator  109  may be a high torque motor that enables the first deformable gripper  104  and the second deformable gripper  106  to achieve strong grasps around various objects. Additionally, in embodiments, idler horns may be installed in association with motors to ensure that loads are adequately supported. 
       FIG.  2    depicts a detailed illustration of various parts of the linkage  200  of the robot end effector  102 , according to one or more embodiments described and illustrated herein. In embodiments, the linkage  200  of the robot end effector  102  may include four components, namely a fixed link component  202 , a plurality of movable link components  204 ,  206 ,  208 , and a plurality of revolving joints. In embodiments, it is noted that the four components of the linkage  200  may be composed of chopped carbon-filled nylon, a composite of Onxy material and embedded continuous fiberglass, or other comparable materials. Additionally, in embodiments, the linkage  200  may be 3D printed, and brass heat-set inserts may be utilized to fasten various components of the linkage  200 . In embodiments, for ensuring frictionless movement of the first deformable gripper  104  and the second deformable gripper  106 , plastic bushings may be positioned in association with the first deformable gripper  104 , the second deformable gripper  106 , and various locations of the robot end effector  102 . In embodiments, the plastic bushings may be paired with or used in association with aluminum shafts in order to design the linkage  200  to be both lightweight and strong. 
     In embodiments, a shaft between the movable link component  204  and the movable link component  206  is maintained in a particular position by retaining ring components and similar shafts are also maintained in place via plastic spacers that are utilized to occupy empty space along axle lengths included as part of the robot end effector  102 . In embodiments, the linkage  200  is less likely to bend or fracture as compared with conventional mechanical components that are similar to the linkage  200 , as the linkage  200  may be composed of aluminum alloys. These alloys also have the added advantage of being only marginally heavier than various plastic components that are more susceptible to fracture. 
       FIG.  3 A  depicts an example implementation of the robot end effector  102  in which the first deformable gripper  104  is positioned at various acute angles relative to the the second deformable gripper  106 . In particular, as illustrated in  FIG.  3 A , orientation  302  corresponds to the first deformable gripper  104  and the second deformable gripper  106  defining an angle between the two grippers of fifteen degrees. Similarly, orientations  304 ,  306 , and  308  correspond to the first deformable gripper  104  and the second deformable gripper  106  defining angles between the two grippers of thirty degrees, forty five degrees, and seventy degrees. It is noted that the first deformable gripper  104  and the second deformable gripper  106  may be oriented in a plurality of acute angles that differ from the angles of the orientations illustrated in  FIG.  3 A . 
       FIG.  3 B  depicts an example implementation of the robot end effector  102  in which the first deformable gripper  104  is positioned at an angle of ninety degrees relative to the second deformable gripper  106  and at an obtuse angle relative to the second deformable gripper  106 . In particular, as illustrated in  FIG.  3 B , the orientations  310  and  312  correspond to the first deformable gripper  104  and the second deformable gripper  106  defining angles between the two grippers of ninety degrees and one hundred and twenty degrees, respectively. 
       FIG.  4    depicts a plurality of example orientations of the robot end effector  102  in which the first deformable gripper  104  and the second deformable gripper  106  interact with, grasp, and are configured to manipulate various objects having dimensions that a significantly larger than the dimensions of the first deformable gripper  104  and the second deformable gripper  106 , and the robot end effector  102 . Regarding example orientation  402 , the controller  114  may send instructions to the actuator  109 , as a result of which the actuator  109  may operate to move the first deformable gripper  104  and the second deformable gripper  106  to a position or orientation defining an angle of approximately ninety degrees. In particular, as illustrated, the first deformable gripper  104  and the second deformable gripper  106  may be oriented around two sides of a particular corner of a box  403  that is disproportionately larger than the dimensions of the robot end effector  102  and the first deformable gripper  104  and the second deformable gripper  106 . In operation, an example process for manipulating the box  403  may include an example orientation  404 , as illustrated in  FIG.  4   , in which the first deformable gripper  104  may bear the weight of the box  403  while the second deformable gripper  106 , positioned at an angle of ninety degrees relative to the first deformable gripper  104 , may serve as a stabilization force to ensure that the position of the box  403  is maintained. Although  FIG.  4    depicts two separate robot end effectors grasping the box  403  on opposite sides of the box  403 , a single robot end effector may be utilized to manipulate and carry the box  403 . In particular, the first deformable gripper  104  and the second deformable gripper  106  may be oriented at an angle such that both the grippers may serve as the base on which box  403  may be positioned. In other words, the box  403  may be tilted upwards at an angle of ninety degrees, with both of the grippers positioned at the base of the box  403 . In other embodiments, in orientation  406 , two robot end effectors are shown as being positioned around corners of a black container box  407  that is also disproportionately larger than each of the deformable grippers of the robot end effectors. 
       FIG.  5    depicts the robot end effector  102  grasping and rotating an example external object  504 , according to one or more embodiments described and illustrated herein. In particular, an example orientation  502  shows the first deformable gripper  104  and the second deformable gripper  106  being moved to define an acute angle that corresponds to approximately ten degrees. It is noted that the first deformable gripper  104  and the second deformable gripper  106  may be positioned such that these grippers firmly grasp the outer surface of the example external object  504 . In example orientation  506 , each of the first deformable gripper  104  and the second deformable gripper  106  are shown as being partially rotated at an angle  508  of approximately twenty degrees. Additionally, the rotating motion of the robot end effector  102  is comparable to a typical rotating movement that may be performed by a wrist of a human being. Such a rotating motion enables the first deformable gripper  104  and the second deformable gripper  106  to grasp items located in areas where a robot may not be able to travel, e.g., around corners of walls, cabinets, and in gaps between walls in a home. 
       FIG.  6    depicts a non-limiting example of the controller  114  that is configured to perform one or more of the features and functionalities described in the present disclosure, according to one or more embodiments described and illustrated herein. As illustrated, the controller  114  includes a processor  606 , input/output hardware  608 , a network interface hardware  610 , a data storage component  612 , and memory  602 . The memory  602  may be configured as volatile and/or nonvolatile memory and as such, may include random access memory (including SRAM, DRAM, and/or other types of RAM), flash memory, secure digital (SD) memory, registers, compact discs (CD), digital versatile discs (DVD) (whether local or cloud-based), and/or other types of non-transitory computer-readable medium. Depending on the particular embodiment, these non-transitory computer-readable media may reside within the computing device and/or a device that is external to the controller  114 . 
     The memory  602  may store operating instructions  603 , each of which may be embodied as a computer program, firmware, and so forth. The memory  602  may comprise RAM, ROM, flash memories, hard drives, or any device capable of storing the operating instructions  603  such that the operating instructions  603  can be accessed by the processor  606 . The operating instructions  603  may comprise logic or algorithm(s) written in any programming language of any generation (e.g., 1GL, 2GL, 3GL, 4GL, or 5GL) such as, for example, machine language that may be directly executed by the controller  114 , or assembly language, object-oriented programming (OOP), scripting languages, microcode, etc., that may be compiled or assembled into machine readable and executable instructions and stored on the memory  602 . Alternatively, the operating instructions  603  may be written in a hardware description language (HDL), such as logic implemented via either a field-programmable gate array (FPGA) configuration or an application-specific integrated circuit (ASIC), or their equivalents. Accordingly, the methods described herein may be implemented in any conventional computer programming language, as pre-programmed hardware elements, or as a combination of hardware and software components. The processor  606  along with the memory  602  may operate as a controller for the controller  114 . 
     A local interface  604  is also included in  FIG.  1    and may be implemented as a bus or other communication interface to facilitate communication among the components of the controller  114 . The processor  606  may include any processing component operable to receive and execute operating instructions  603  from the memory  602  (such as from a data storage component  612  and/or the memory  602 ). Accordingly, the processor  606  may be an integrated circuit, a microchip, a computer, or any other computing device. As described above, the input/output hardware  608  may include and/or be configured to interface with speakers, microphones, and/or other input/output components. 
     The operating instructions  603  may include an operating system and/or other software for managing components of the controller  114 . It should be understood that while the component in  FIG.  1    are illustrated as residing within the controller  118 , this is merely an example. In some embodiments, one or more of the components may reside external to the controller  114  or within other devices. It should be understood that, while the controller  114  is illustrated as a single device, this is also merely an example. As an example, one or more of the functionalities and/or components described herein may be provided by the controller  114 . Depending on the particular embodiments, any of these devices may have similar components as those depicted in  FIG.  1   . To this end, any of these devices may include instructions for performing the functionality described herein. 
     It should now be understood that the embodiments of the present disclosure are directed to robot end effectors. The robot end effectors comprise a first deformable gripper, a second deformable gripper coupled to the first deformable gripper by a linkage, and an actuator coupled to the linkage and operable to move at least one of the first deformable gripper and the second deformable gripper to a position defining an angle between the first deformable gripper and the second deformable gripper that is greater than or equal to 130 degrees. In other embodiments, the robot end effector comprises a first deformable gripper, a second deformable gripper coupled to the first deformable gripper by a linkage, and an actuator coupled to the linkage and operable to move at least one of the first deformable gripper and the second deformable gripper to: a fully open defining an angle between the first deformable gripper and the second deformable gripper that is greater than or equal to 130 degrees, and a half open position defining an additional angle between the first deformable gripper and the second deformable gripper that is approximately 90 degrees. 
     In a first aspect, a robot end effector comprises a first deformable gripper, a second deformable gripper coupled to the first deformable gripper by a linkage, and an actuator coupled to the linkage and operable to move at least one of the first deformable gripper and the second deformable gripper to a position defining an angle between the first deformable gripper and the second deformable gripper that is greater than or equal to 130 degrees. 
     In a second aspect, the robot end effector of the first aspect, wherein the linkage is a four-component linkage that includes a fixed link component, and a plurality movable link components. 
     In a third aspect, the robot end effector of the second aspect, wherein the linkage is composed of carbon filled nylon. 
     In a fourth aspect, the robot end effector of any of the first to the third aspects, wherein each of the first deformable gripper and the second deformable gripper include an acrylic base and a deformable surface disposed therein, the deformable surface is composed of latex. 
     In a fifth aspect, the robot end effector of the fourth aspect, wherein the deformable surface of each of the first deformable gripper and the second deformable gripper includes a pattern embedded thereupon. 
     In a sixth aspect, the robot end effector of the fifth aspect, further comprising a camera that is configured to capture one or more images of an object contacting the pattern embedded on the deformable surface of each of the first deformable gripper and the second deformable gripper. 
     In a seventh aspect, the robot end effector of the sixth aspect, wherein the camera is positioned on the acrylic base included in each of the first deformable gripper and the second deformable gripper. 
     In an eighth aspect, the robot end effector of any of the first to the fifth aspects, further comprising plastic bushings positioned in association with each of the linkage, the first deformable gripper, and the second deformable gripper. 
     In a ninth aspect, the robot end effector of any of the first to the eighth aspects, wherein the actuator is operable to move the first deformable gripper and the second deformable gripper to a fully open position, a half-open position, and a fully closed position. 
     In a tenth aspect, the robot end effector of the ninth aspect, wherein the fully open position corresponds to the position defining the angle between the first deformable gripper and the second deformable gripper that is greater than or equal to 130 degrees. 
     In an eleventh aspect, the robot end effector of the ninth aspect, wherein the half-open position corresponds to an additional position defining an additional angle between the first deformable gripper and the second deformable gripper that is approximately 90 degrees. 
     In a twelfth aspect, a robot end effector comprises a first deformable gripper, a second deformable gripper coupled to the first deformable gripper by a linkage, and an actuator coupled to the linkage and operable to move at least one of the first deformable gripper and the second deformable gripper to: a fully open defining an angle between the first deformable gripper and the second deformable gripper that is greater than or equal to 130 degrees, and a half open position defining an additional angle between the first deformable gripper and the second deformable gripper that is approximately 90 degrees. 
     In a thirteenth aspect, the robot end effector of the twelfth aspect, wherein the linkage is a four-component linkage that includes a fixed link component, and a plurality movable link components. 
     In a fourteenth aspect, the robot end effector of the thirteenth aspect, wherein the linkage is composed of carbon filled nylon. 
     In a fifteenth aspect, the robot end effector of any of the twelfth to the fourteenth aspects, wherein each of the first deformable gripper and the second deformable gripper include an acrylic base and a deformable surface disposed therein, the deformable surface is composed of latex. 
     In a sixteenth aspect, the robot end effector of the fifteenth aspect, wherein the deformable surface of each of the first deformable gripper and the second deformable gripper includes a pattern embedded thereupon. 
     In a seventeenth aspect, the robot end effector of the sixteenth aspect, further comprising a camera that is configured to capture one or more images of an object contacting the pattern embedded on the deformable surface of each of the first deformable gripper and the second deformable gripper. 
     In an eighteenth aspect, the robot end effector of the seventeenth aspect, wherein the camera is positioned on the acrylic base included in each of the first deformable gripper and the second deformable gripper. 
     In a nineteenth aspect, the robot end effector of any of the twelfth to the eighteenth aspects, further comprising plastic bushings positioned in association with each of the linkage, the first deformable gripper, and the second deformable gripper. 
     In a twentieth aspect, the robot end effector of any of the twelfth to the nineteenth aspect, wherein the actuator is operable to move the first deformable gripper and the second deformable gripper to a fully open position, half-open position, and fully closed position. 
     The terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms, including “at least one,” unless the content clearly indicates otherwise. “Or” means “and/or.” As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. It will be further understood that the terms “comprises” and/or “comprising,” or “includes” and/or “including” when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof. The term “or a combination thereof” means a combination including at least one of the foregoing elements. 
     It is noted that the terms “substantially” and “about” may be utilized herein to represent the inherent degree of uncertainty that may be attributed to any quantitative comparison, value, measurement, or other representation. These terms are also utilized herein to represent the degree by which a quantitative representation may vary from a stated reference without resulting in a change in the basic function of the subject matter at issue. 
     While particular embodiments have been illustrated and described herein, it should be understood that various other changes and modifications may be made without departing from the spirit and scope of the claimed subject matter. Moreover, although various aspects of the claimed subject matter have been described herein, such aspects need not be utilized in combination. It is therefore intended that the appended claims cover all such changes and modifications that are within the scope of the claimed subject matter.