Origami Chomper‐Based Flexible Gripper with Superior Gripping Performances

Flexible grippers with superior gripping capabilities are essential for carrying objects. Herein, an origami chomper‐based flexible gripper is designed using a combination of the origami technique and a newly developed nonlinear topology optimization method. This novel origami chomper‐based flexible gripper exhibits superior gripping performance, as revealed by a series of experiments, including gripping range capability under an identical input load, maximum gripping ratio, gripping adaptability, and achieving richer gripping characteristics by size scaling. The origami chomper‐based flexible gripper can handle a wide range of object irregularities in textures and uneven shapes and can enable effective gripping of objects across scales from millimeters to centimeters to decimeters through size scaling. This study paves the way for innovative high‐performance designs of flexible grippers.


Introduction
[4][5] An essential aspect of these advantages is that their flexibility allows for geometrically large deformations.However, a purely flexible robot gripper normally suffers from two limitations: (1) it is susceptible to damage by sharp objects under large geometric deformations, and (2) its load-bearing capacity is weak.Therefore, the design of robotic grippers requires a balance between flexibility and rigidity.
[28][29] For example, an origami-inspired reconfigurable suction gripper was designed to handle objects with challenging geometries. [30][33][34][35][36][37][38] Although the aforementioned origami robot grippers enable the grasping of objects with different stiffnesses, shapes, sizes, and weights, they are all based on empirical designs.In addition, they tended to approximate the crease as a hinge.This inadvertently limits the performance of origami robot grippers. [39,40]One potential approach is to use a structural optimization method, driven by gripping performance, to orient the creases of the crease pattern of the origami grippers.There are two available alternatives for altering crease characteristics: changing the material at the crease and Flexible grippers with superior gripping capabilities are essential for carrying objects.Herein, an origami chomper-based flexible gripper is designed using a combination of the origami technique and a newly developed nonlinear topology optimization method.This novel origami chomper-based flexible gripper exhibits superior gripping performance, as revealed by a series of experiments, including gripping range capability under an identical input load, maximum gripping ratio, gripping adaptability, and achieving richer gripping characteristics by size scaling.The origami chomper-based flexible gripper can handle a wide range of object irregularities in textures and uneven shapes and can enable effective gripping of objects across scales from millimeters to centimeters to decimeters through size scaling.This study paves the way for innovative high-performance designs of flexible grippers.
modifying the geometric configuration of the crease.Changing the material properties at the crease may lead to manufacturing difficulties owing to multimaterial fabrication. [41]Therefore, altering the geometric configuration of the crease is preferable.53][54][55][56][57][58] Although these optimized robot grippers yield significant performance improvements, the optimization process assumes a linear relationship.Considering the considerable deformation characteristics of flexible robot grippers, linear assumptions may result in inaccurate or underperforming designs.Therefore, this study attempted to use nonlinear topology optimization (NTO) methods [59][60][61][62][63][64][65][66][67] to improve the performance of origami grippers more accurately.Considering the refinement design requirements of origami grippers and computationally costly NTO, we adopted a multiresolution strategy in the NTO.[70] In this context, we propose a novel NTO method for compliant mechanisms based on an additive hyperelasticity technique [64,65] and a multiresolution strategy. [68]Further, we use the novel NTO method to optimize an origami chomper-based flexible gripper to reassign materials at the creases.Unlike most previous studies that regarded creases as straight or curved lines, [71][72][73] this study considers the geometric characteristics of creases.We fabricate prototypes of the optimized origami chomper-based flexible gripper using a laser cutter, followed by testing various gripping performances, including gripping range capability under an identical input load, maximum gripping ratio, gripping adaptability, and richer gripping characteristics by size scaling.This demonstrates that the optimized origami chomper-based flexible gripper exhibits excellent gripping performance.Moreover, we show that removing inefficient material from the creases using NTO can lead to a more significant output displacement (better gripping range capability) relative to the initial origami chomper-based flexible gripper for an identical input load.
We would like to emphasize that the innovation of the work in this article is twofold.First, the origami chomper-based flexible gripper form chosen for this paper is much simpler, with only four mountain creases and one valley crease.The existing literature has more creases in the flexible origami grippers, which undoubtedly poses a challenge to the mechanical characterization of the flexible grippers and the optimal design.Therefore, it is readily apparent that most existing work stays in empirical design.Second, this study proposes a NTO method applied to the performance enhancement of flexible origami grippers, aiming to address the unreasonable linearity assumption of the existing literature on the optimal design of flexible grippers.Besides, the innovation of the NTO method is summarized as follows.The method is implemented under the density-based topology optimization framework and considers geometric and material nonlinearities.The algorithm utilizes a multiresolution design strategy and additive hyperelasticity technique to reduce the computational burden of NTO and address the algorithm convergence challenge caused by large deformations.The basic idea for enhancing computational efficiency, mathematical modeling, and sensitivity analysis is presented in S1, Supporting Information.
2. Design for the Origami Chomper-Based Flexible Gripper In the Plants versus Zombies game, a big mouth flower called "Chomper" can swallow zombies in one bite.It is similar to a flytrap, such that the mouth can be opened and closed to eat objects; however, it can also grip objects. [74]Figure 1a shows the two different opening and closing states of the mouth of the "Chomper" toy.A similar construction can be achieved using origami techniques, i.e., an origami chomper.We show two different states of the origami chomper similar to the "Chomper" toy in Figure 1b.The opening and closing of the origami chomper can be readily achieved by applying and releasing pressure on vertices 1 and 2 using fingers.However, the folding of this origami chomper was relatively complicated.Inspired by the "Chomper" toy and relatively complicated origami chomper, another simplified origami chomper can achieve a similar function by simply adding one valley crease and four mountain creases to a thin sheet, as shown in Figure 1c.The crease pattern is shown in Figure 1d.Note that Figure 1b is more like the chomper than Figure 1c.However, the chomper in Figure 1b has more creases, undoubtedly challenging the mechanical characteristics of flexible grippers and their optimal design.The empirical design of Figure 2b is not difficult, but the accurate mechanical characterization is challenging.For instance, the origami structure of Figure 2b has undergone contact between facets, and complex mechanical behaviors such as friction and slippage may occur during the gripping process.Without an accurate mechanical characterization, an optimal design cannot be performed.Thus, we further simplify the chomper in Figure 1b and use the one shown in Figure 1c in this study.This simplified structure in Figure 1c retains the functionality of the chomper while being easier to design and manufacture.
Analogous to the relatively complicated origami chomper, using the fingers to apply pushing force to the upper and lower boundary lines of the simplified origami chomper, its folding angle changed from θ 1 to θ 2 (θ 1 > θ 2 ), and the origami chomper closed, completing the process of gripping the object; conversely, the origami chomper opened, completing the process of releasing the object.However, when using such structures for gripping objects, there are drawbacks such as a low gripping range capability under identical input loads, as demonstrated in Subsection 4.2.1.Thus, an NTO design is required for the origami chomper to enhance gripping performance.In addition, crease stiffness dominated the deformation of the origami structure.In contrast, a crease in a conventional origami structure is often a straight or curved line with no geometric features.To maximize the performance, the crease of our origami chomper-based flexible gripper is a predefined area with geometric features, as illustrated in  .The black area represents the facet, and the white area represents the crease.In addition, two hollow areas are predefined to facilitate folding.Because engineering materials generally have a certain thickness, the thicknesses of the facets and creases in this study can be identical or different, as shown in the subsequent prototype preparation and experiments.We subsequently eliminated inefficient materials at the creases using NTO to achieve the desired gripping performance.

Novel Design Method for the Origami Chomper-Based Flexible Gripper
The origami chomper-based flexible gripper can be considered as a compliant mechanism; thus, we first introduce a novel design method (NTO method) for optimizing compliant mechanisms, including the basic idea for enhancing computational efficiency, mathematical modeling, and sensitivity analysis.We then developed a novel design method to design an origami chomper-based flexible gripper to identify the optimum arrangement of the material at the crease to satisfy the desired gripping properties (the detailed design parameters are shown in Figure 2a and S2, Supporting Information).Before optimizing the origami chomper-based flexible gripper, we used two benchmark examples of compliance mechanisms to demonstrate the validity of the proposed NTO approach: displacement inverter and gripper mechanisms (S3, Supporting Information).
Figure 2b shows the optimized origami chomper-based flexible gripper after redistributing the materials in the crease regions.The upper and lower panels show the 3D and vertical views, respectively.It can be observed that some material was removed from the crease to achieve the maximum output end displacement.The removal of material from the crease reduces the stiffness of the origami chomper-based flexible gripper, which, in turn, increases the output displacement at the end.In addition, it can be observed from the optimized topological boundary that we used very fine material elements, which strongly facilitated subsequent postprocessing and fabrication.This is also the superiority of our proposed method, i.e., it can achieve both high-efficiency and high-resolution in dealing with nonlinear problems.To monitor the convergence characteristics of the algorithm throughout the NTO process, the historical iteration plots of the optimization objective (output displacement) and constraint function (volume fraction) are shown in Figure 2c.The output displacement gradually converges to À3.4 mm with increasing iteration steps, while the material volume constraint finally stabilizes at approximately 60%, confirming the excellent convergence characteristics of the proposed algorithm.Because we focused on evaluating the grasping capacity of the origami chomper-based flexible gripper with an identical input force, we increased the input force to 25 N for comparison purposes and compared the displacement at the end of the origami chomper-based flexible gripper before and after performing NTO. Figure 2d  We considered two types of origami chomper-based flexible grippers, type I and type II.Type I was made of thin and thick PVC sheets glued together, where only the thin PVC sheet was used at the creases, and a thick PTV sheet was employed to thicken the facets.In contrast, type II was fabricated using only thin PVC sheets.We mimicked the dimensions of a human hand to approximate the size of the origami chomper-based flexible gripper.The origami chomper-based flexible gripper can be considered a 2D structure in an unfolded state.The geometric dimensions of the initial configuration in the xOy plane are shown in Figure 3a. Figure 3b shows the prototype of the initial configuration of the type I origami chomper-based flexible gripper.We performed NTO on a type I origami chomper-based flexible gripper to remove unnecessary materials at the creases and obtain an optimized type I origami chomper-based flexible gripper.We used a laser cutter to eliminate inefficient material in the crease region to obtain a prototype of the optimized type I origami cutting-based flexible gripper, as shown in Figure 3c.We obtained the prototype of the optimized type II origami chomper-based flexible gripper using an identical NTO method and fabrication process, as depicted in Figure 3d.It should be noted that the connection structures at the creases are more prone to fatigue damage, which are beyond the scope of this paper and will be explored in the future.

Gripping Range Capability under an Identical Input Load
We tested the gripping range capacity of the optimized origami chopper-based flexible gripper under identical input loads.A digital pressure tester (Type: DS2-20N-X, ZHIQU Precision Instrument, China) equipped with a force sensor was employed to measure the contact force between the type I origami chomper-based flexible gripper and the fixed bracket, as shown in Figure 4a.The maximum load of the digital pressure tester was 20 N with an accuracy of 0.01 N, and the sampling frequency was 1000 times s À1 .A digital pressure tester can facilitate convenient and highly accurate control of the input load of an origami chomper-based flexible gripper.To ensure the mounting accuracy and accuracy of the measured force, the fixed bracket and origami chomper-based flexible gripper were connected by a thick PVC sheet in the middle and fixed using bolts and nuts, as shown in Figure 4b.A force sensor was mounted on one of the inputs to the origami chomper-based flexible gripper.During the test, we grasped the two inputs of the origami chomper-based flexible gripper with our fingers, and the force sensor measured the magnitude of the input force.Figure 4c,d illustrates the gripping states of the origami chopper-based flexible gripper before and after applying NTO with an input load of 4 N, respectively.We define the distance between the two gripping points of the origami chomper-based flexible gripper as the gripping length, and the value in the initial state is approximately 192 mm (this value is unreachable in principle), as shown in Figure 3a.In the input force range of 0-4 N, the gripping length of the optimized origami chomper-based flexible gripper varied from 16 to 192 mm, demonstrating the advantage of achieving a large gripping range with a small input force.In contrast, the gripping length of the initial origami chomper-based flexible gripper could only be altered within a very small range, i.e., from 165 to 192 mm.This can be attributed to the removal of inefficient material at the creases by the NTO, which leads to a more significant output displacement relative to the initial origami chomper-based flexible gripper for an identical input load.

Maximum Gripping Ratio
Because type II is much lighter than the type I origami chomperbased flexible gripper, we examined the maximum gripping ratio characteristics using the former.We defined the gripping ratio as  the weight of the gripped object divided by the weight of the optimized type II origami chomper-based flexible gripper.The object was a transparent plastic cup containing sand grains, as shown in Figure 5a.It was found that the optimized type I origami chomper-based flexible gripper could grip a transparent plastic cup with sand grains easily and firmly because of the cylindrical envelope formed by the flexible gripper during the gripping process, as shown in Figure 5b.To achieve the maximum gripping ratio, sand was gradually added to the transparent plastic cup until it could not be gripped.At this point, the transparent plastic cup with sand grains weighed 113.88 g, as shown in Figure 5c.The maximum gripping ratio can be calculated as 113.88 g/3.95 g = 28.83,where 3.95 g is the weight of the optimized type II origami chomper-based flexible gripper, as shown in Figure 5d.Therefore, an origami chomper-based flexible gripper can be designed using the proposed NTO method, with a maximum gripping ratio of 28.83.

Gripping Adaptability
We studied the capacity of the optimized type II origami domain-based flexible gripper to grip objects with different stiffnesses, shapes, weights, and sizes, that is, gripping adaptability.We used this flexible gripper as the end actuator of a robotic arm to achieve a continuous wide range of motion in space to grasp fragile and irregular objects.Figure 6a shows an overall installation diagram of the optimized type-II origami chomperbased flexible gripper.The proposed flexible gripper was installed on the end actuator of a robotic arm (Robot Anno V6-PLUS, Shenzhen, China) via fixation and actuation parts.The fixation and actuation parts mainly include the bracket, linear actuator, push rod, slider, slider guide, push rod end connection, limit frame, and hinge, as shown in Figure 6b,c.A bracket connected to the end of the robot arm was used to fasten the linear actuator and the slide guide.The linear actuator pushes the push rod along with the slider to move linearly in the slide guide, and the movement position is limited by the limit frame.The push rod end connection and hinge realize the connection between the push rod and the optimized type II origami chomper-based flexible gripper, which can fulfill the angle change between the push and rod end connection and the facet of the flexible gripper during the loading process.Screw bolts and nuts were used to connect the parts.Thus, when driven by a linear actuator, a flexible gripper can be used to grip objects.The push rod end connection, slider, and slider guide guarantee that both ends of the push rod are at identical heights, thus preventing the flexible gripper from deflecting and failing to hold the object stably during the gripping process.7 illustrates that the optimized type II origami chomper-based flexible gripper can successfully grip various objects with different stiffnesses, shapes, weights, sizes, and orientations, especially brittle objects, irregularities in textures, and uneven shapes.The gripped objects were carefully selected.This include a balloon, table tennis ball, pendant, cherry tomato, egg, Bluetooth headset, orange (different orientations), plastic bottle (different orientations), and rubber duck, as shown in Figure 7a-l.The relevant parameters are summarized in Table S1, Supporting Information.Through careful observation of the gripping process, the proposed flexible gripper fits the object well, thus achieving stable gripping for a wide range of shapes.In addition, when the size of the gripped object was relatively small, the proposed flexible gripper wrapped its lower part, generating an upward support force and less pressure on the object during the gripping process, as shown in Figure 7b,d.This has two advantages.On the one hand, it effectively protects the gripped object.On the other hand, it increases the maximum gripping ratio.Moreover, when gripping less rigid, soft, or brittle objects, it was possible to achieve stable gripping and effectively avoid damaging the object, as shown in Figure 7a,b,d,e,l.This was attributed to the excellent flexibility of the proposed gripper.Finally, because of the large gripping range of the proposed flexible gripper and its applicability to different object shapes, the gripping of objects with irregular textures (Figure 7c) and different orientations (Figure 7g-i) can be achieved.Consequently, selecting a specific orientation when gripping an object is not necessary; thus, the gripping process can be easily and quickly realized.We show a few representative processes for gripping objects in Movie S1-S8, Supporting Information, for a balloon, table tennis ball, pendant, cherry tomato, egg, horizontally arranged orange, vertically arranged orange, and rubber duck.To further demonstrate the powerful gripping adaptability of the proposed flexible gripper, the tissue extraction process is shown in Figure 7m (Movie S9, Supporting Information).It can be observed that the extraction of the tissue fully mimics the human hand.

Achieving Richer Gripping Characteristics by Size Scaling
To further confirm that the origami chomper-based flexible gripper proposed in this study can achieve richer gripping characteristics through size scaling, that is, handling more challenging object geometries, two and one-half sizes of the original flexible gripper were prepared by linear scaling and tested for their gripping range.To facilitate later descriptions, these two new flexible grippers are referred to as large-and small-scale flexible grippers.The large-scale flexible gripper could grip a large plastic bottle (vs Figure 7j), a large rubber duck (vs Figure 7l), and a cardboard box smoothly and firmly, as shown in Figure 8a-c.The gripping lengths of the three objects were 85, 95, and 135 mm.The small-scale flexible gripper gripped the sand grain, M1 nut, pill, and soft rubber balls of sizes 0.8, 2.5, 10.5, and 12 mm, as shown in Figure 8d-g.Therefore, the proposed flexible gripper can effectively grip objects across scales ranging from millimeters to centimeters and decimeters through size scaling.This has rarely been observed in existing studies.

Conclusion
We propose a novel origami chomper-based flexible gripper that combines the origami technique and a newly developed NTO method.The proposed NTO method for compliant mechanisms has many advantages, such as being computationally efficient, exhibiting excellent convergence, and enabling a refined design.This design method was applied to an origami chomper-based flexible gripper.We fabricated several optimized origami chomper-based flexible grippers and conducted a series of experiments to demonstrate their excellent gripping performances.We demonstrated that removing the inefficient material at the creases using the NTO method can result in a better gripping range capability under an identical input load relative to the initial origami chomper-based flexible grippe.In addition, the optimized origami chomper-based flexible gripper exhibited a maximum gripping ratio of 28.83.It can successfully grip a wide range of objects with different stiffnesses, shapes, weights, sizes, and orientations, particularly those with irregular textures and uneven shapes.Moreover, the proposed flexible gripper can effectively grip objects across scales ranging from millimeters to centimeters to decimeters through size scaling (more challenging object geometries).Finally, we demonstrated that the performance of flexible grippers can be substantially improved by incorporating simple origami structures (e.g., origami grippers) and the NTO method.Note that the clamping force is an important indicator for flexible grippers.However, the present work focuses mainly on studying the clamping range and the clamping capacity for different objects, which is realized by the proposed NOT method and origami technique.The clamping force is not considered an optimization objective.However, the excellent clamping force has been demonstrated from the side using the gripping ratio in the experimental test.

Figure 1 .
Figure 1.Inspiration of the origami chomper-based flexible gripper.a) The "Chomper" toy.Its mouth can be opened and closed to grip objects.b) A relatively complicated origami chomper.The opening and closing of the origami chomper can be readily achieved by applying pressure and releasing pressure on Vertex 1 and Vertex 2 using the fingers.c) A simplified origami chomper.Using the fingers to apply pushing force to the upper and lower boundary lines of the simplified origami chomper, its folding angle changes from θ 1 to θ 2 and the origami chomper closes, completing the process of gripping the object.d) The crease pattern of the simplified origami chomper, which includes one valley crease and four mountain creases.e) The crease pattern of the origami chomper-based flexible gripper.The black area represents the facet, while the white area represents the crease, which is a predefined area with geometric features.In addition, two hollow areas are predefined to facilitate folding (red area).

Figure 2 .
Figure 2. NTO of the origami chomper-based flexible gripper.a) Initial design domain, including the geometric dimensions, loading, and boundary conditions.b) Optimized origami chomper-based flexible gripper after redistributing the materials in the crease regions.Upper panel: 3D perspective and lower panel: vertical view.c) Historical iteration plots of the optimization objective and constraint function.d) Deformation of the origami chomperbased flexible gripper.Left panel: origami chomper-based flexible gripper before performing NTO, and right panel: origami chomper-based flexible gripper after performing NTO.

Figure 1e
Figure1e.The black area represents the facet, and the white area represents the crease.In addition, two hollow areas are predefined to facilitate folding.Because engineering materials generally have a certain thickness, the thicknesses of the facets and creases in this study can be identical or different, as shown in the subsequent prototype preparation and experiments.We subsequently eliminated inefficient materials at the creases using NTO to achieve the desired gripping performance.
displays the deformation nephogram of the flexible gripper (unit: meter), showing that that the displacements at the end of the origami chomper-based flexible gripper before and after performing NTO are À14.34 and À42.01 mm, respectively, improved by about 193%, evidently demonstrating NTO effectively increases the displacement of the endpoint of the origami chomper-based flexible gripper under a given load condition.This also reflects the fact that NTO can significantly strengthen the grasping capacity of origami chomper-based flexible grippers.3.Experimental Testing of the Origami Chomper-Based Flexible Gripper 3.1.Fabrication of the Origami Chomper-Based Flexible Gripper

Figure 3 .
Figure 3. Fabrication of optimized origami chomper-based flexible gripper.a) Geometric dimensions of the initial configuration in the xOy plane.Origami chomper-based flexible gripper can be considered a 2D structure before folding.b) Prototype of the initial configuration of type I origami chomper-based flexible gripper.It was made of a thin PVC sheet and a thick PVC sheet glued together, where only the thin PVC sheet was used at the creases.We used a thick PTV sheet to thicken the facets.Note that the facets are excluded from the NTO process.c) Prototype of the optimized type I origami chomper-based flexible gripper.We remove the material at the crease by laser cutting.d) Prototype of the optimized type II origami chomper-based flexible gripper.We only used thin PVC sheets and removed the material at the creases using laser cutting.

Figure 4 .
Figure 4. Gripping range capability under identical input load.a) A digital pressure tester includes a force sensor for measuring the contact force between the type I origami chomper-based flexible gripper and the fixed bracket.b) Experimental setup for testing the gripping range capability.The force sensor is mounted on a fixed bracket.To ensure mounting accuracy, the fixed bracket and the origami chomper-based flexible gripper are connected by a thick PVC sheet in the middle and fixed by bolts and nuts.c) Gripping range capability of the initial type I origami chomper-based flexible gripper with an applied load of 4 N.The gripping length was altered from 192 to 165 mm.d) Gripping range capability of the optimized Type I origami chomper-based flexible gripper with an applied load of 4 N.The gripping length is changed from the starting 192 to 16 mm.
Figure 6d shows the actual prototype installation diagram of the proposed flexible gripper.To observe the installation more clearly, Figure 6e-g presents the front view, left view, and a closer look at the mounting position of the flexible gripper.

Figure 5 .
Figure 5. Maximum gripping ratio testing of the optimized type II origami chomper-based flexible gripper.a) Using the optimized type II origami chomper-based flexible gripper to grip a transparent plastic cup with sand grains.b) The cylindrical envelope formed during the gripping process, which allows it to hold objects firmly.c) The weight of the transparent plastic cup with sand grains is 113.88 g.This is the maximum weight that can be gripped.d) The optimized Type II origami chomper-based flexible gripper weights 3.95 g.

Figure
Figure7illustrates that the optimized type II origami chomper-based flexible gripper can successfully grip various objects with different stiffnesses, shapes, weights, sizes, and orientations, especially brittle objects, irregularities in textures, and uneven shapes.The gripped objects were carefully selected.This include a balloon, table tennis ball, pendant, cherry tomato, egg, Bluetooth headset, orange (different orientations), plastic bottle (different orientations), and rubber duck, as shown in Figure7a-l.The relevant parameters are summarized in TableS1, Supporting Information.Through careful observation of the gripping process, the proposed flexible gripper fits the object well, thus achieving stable gripping for a wide range of shapes.In addition, when the size of the gripped object was relatively small, the proposed flexible gripper wrapped its lower part, generating an upward support force and less pressure on the object during the gripping process, as shown in Figure7b,d.This has two advantages.On the one hand, it effectively protects the gripped object.On the other hand, it increases the maximum gripping ratio.Moreover, when gripping less rigid, soft, or brittle objects, it was possible to achieve stable gripping and effectively avoid damaging the object, as shown in Figure7a,b,d,e,l.This was attributed to the excellent flexibility of the proposed gripper.Finally, because of the large gripping range of the proposed flexible gripper and its applicability to different object shapes, the gripping of objects with irregular

Figure 6 .
Figure 6.Gripping adaptability testing setup of the optimized type II origami chomper-based flexible gripper.a) Overall installation diagram of the flexible gripper.b) Schematic diagram of the fixation and actuation of the flexible gripper, and c) the view from the bottom up.The fixation and actuation part mainly consists of the bracket, liner actuator, push rod, slider, slider guide, push rod end connection, limit frame, and hinge.d) A real prototype installation diagram of the flexible gripper, with e) the front view, f ) left view, and g) a closer look at the mounting position of the flexible gripper.

Figure 7 .
Figure 7. Gripping adaptability tests by various objects: a) balloon; b) table tennis ball; c) pendant; d) cherry tomato; e) egg; f ) Bluetooth headset; g) horizontally arranged orange; h) vertically arranged orange; i) vertically arranged plastic bottle; j) a plastic bottle placed with the bottom facing outward; k) horizontally arranged plastic bottle; l) rubber ducks; and m) process of extracting tissue.

Figure 8 .
Figure 8. Achieving richer gripping characteristics by scale scaling.Large-scale flexible gripper for gripping a) large plastic bottle (vs Figure 7j); b) large rubber duck (vs Figure 7l); c) cardboard box.Small-scale flexible gripper for gripping d) sand grain; e) M1 nut; f ) pill; and g) soft rubber ball.