HybGrip: a synergistic hybrid gripper for enhanced robotic surgical instrument grasping.

PURPOSE: A fundamental task of a robotic scrub nurse is handling surgical instruments. Thus, a gripper capable of consistently grasping a wide variety of tools is essential. We introduce a novel gripper that combines granular jamming and pinching technologies to achieve a synergistic improvement in surgical instrument grasping. METHODS: A reliable hybrid gripper is constructed by integrating a pinching mechanism and a standard granular jamming gripper, achieving enhanced granular interlocking. For our experiments, our prototype is affixed to the end-effector of a collaborative robot. A novel grasping strategy is proposed and utilized to evaluate the robustness and performance of our prototype on 18 different surgical tools with diverse geometries. RESULTS: It is demonstrated that the integration of the pinching mechanism significantly enhances grasping performance compared with standard granular jamming grippers, with a success rate above 98%. It is shown that with the combined use of our gripper with an underlying grid, i.e., a complementary device placed beneath the instruments, robustness and performance are further enhanced. CONCLUSION: Our prototype's performance in surgical instrument grasping stands on par with, if not surpasses, that of comparable contemporary studies, ensuring its competitiveness. Our gripper proves to be robust, cost-effective, and simple, requiring no instrument-specific grasping strategies. Future research will focus on addressing the sterilizability of our prototype and assessing the viability of the introduced grid for intra-operative use.

A bioinspired stiffness tunable sucker for passive adaptation and firm attachment to angular substrates.

The ability to adapt and conform to angular and uneven surfaces improves the suction cup's performance in grasping and manipulation. However, in most cases, the adaptation costs lack of required stiffness for manipulation after surface attachment; thus, the ideal scenario is to have compliance during adaptation and stiffness after attachment to the surface. Inspired by the capability of stiffness regulation in octopus suction cup, this article presents a suction cup that adapts to steep angular surfaces due to compliance and has high stiffness after attachment. In this design, the stiffness after attachment is provided by using granular jamming as vacuum driven stiffness modulation. Thus, the design is composed of a conventional active suction pad connected to a granular stalk, emulating a hinge behavior during adaptation and creating high stiffness by jamming granular particles driven by the same vacuum as the suction pad. During the experiment, the suction cup can adapt to angles up to 85° with a force lower than 0.5 N. We also investigated the effect of granular stalk's length on the adaptation and how this design performs compared to passive adaptation without stiffness modulation.

Cyclic Loading of Jammed Granular Systems.

This article describes the cyclic loading of jammed granular systems represented by vacuum-packed particles in compression and tension, focusing on the influence of the properties of the granular material on the mechanical response. A jammed granular system is represented by a cylindrical sample filled with polymer granules (vacuum-packed particles) and is examined in symmetric cyclic compression and tension for up to 2000 cycles and at selected values of underpressure, i.e., 0.01, 0.04 and 0.07 MPa. Force and displacement are analyzed during the test, as well as changes in granule morphology by means of microscopic observations. The conducted tests indicate that it is possible to acquire repetitive results of maximum forces in the analyzed loading rage with the condition that granules do not plasticize during loading, i.e., they are resistant to damage during loading.

Pump Up the Jam: Granular Media as a Quasi-Hydraulic Fluid for Independent Control Over Isometric and Isotonic Actuation.

Elastomer-granule composites have been used to switch between soft and stiff states by applying negative pressure differentials that cause the membrane to squeeze the internal grains, inducing dilation and jamming. Applications of this phenomenon have ranged from universal gripping to adaptive mobility. Previously, the combination of this jamming phenomenon with the ability to transport grains across multiple soft actuators for shape morphing has not yet been demonstrated. In this paper, the authors demonstrate the use of hollow glass spheres as granular media that functions as a jammable "quasi-hydraulic" fluid in a fluidic elastomeric actuator that better mimics a key featur of animal musculature: independent control over i) isotonic actuation for motion; and ii) isometric actuation for stiffening without shape change. To best implement the quasi-hydraulic fluid, the authors design and build a fluidic device. Leveraging this combination of physical properties creates a new option for fluidic actuation that allows higher specific stiffness actuators using lower volumetric flow rates in addition to independent control over shape and stiffness. These features are showcased in a robotic catcher's mitt by stiffening the fluid in the glove's open configuration for catching, unjamming the media, then pumping additional fluid to the mitt to inflate and grasp.

One-Shot 3D-Printed Multimaterial Soft Robotic Jamming Grippers.

Soft gripping provides the potential for high performance in challenging tasks through morphological computing; however, design explorations are limited by a combination of a difficulty in generating useful models and use of laborious fabrication techniques. We focus on a class of grippers based on granular jamming that are particularly difficult to model and introduce a "one shot" technique that exploits multimaterial three-dimensional (3D) printing to create entire grippers, including membrane and grains, in a single print run. This technique fully supports the de facto physical generate-and-test methodology used for this class of grippers, as entire design iterations can be fitted onto a single print bed and fabricated from Computer-Aided Design (CAD) files in a matter of hours. Initial results demonstrate the approach by rapidly prototyping in materio solutions for two challenging problems in unconventional design spaces; a twisting gripper that uses programmed deformations to reliably pick a coin, and a multifunctional legged robot paw that offers the ability for compliant locomotion over rough terrains, as well as being able to pick objects in cluttered natural environments. The technique also allows us to easily characterize the design space of multimaterial printed jamming grippers and provide some useful design rules. The simplicity of our technique encourages and facilitates creativity and innovation. As such, we see our approach as an enabling tool to make informed principled forays into unconventional design spaces and support the creation of a new breed of novel soft actuators.

Perception by Palpation: Development and Testing of a Haptic Ferrogranular Jamming Surface.

Tactile hands-only training is particularly important for medical palpation. Generally, equipment for palpation training is expensive, static, or provides too few study cases to practice on. We have therefore developed a novel haptic surface concept for palpation training, using ferrogranular jamming. The concept's design consists of a tactile field spanning 260 x 160 mm, and uses ferromagnetic granules to alter shape, position, and hardness of palpable irregularities. Granules are enclosed in a compliant vacuum-sealed chamber connected to a pneumatic system. A variety of geometric shapes (output) can be obtained by manipulating and arranging granules with permanent magnets. The tactile hardness of the palpable output can be controlled by adjusting the chamber's vacuum level. A psychophysical experiment (N = 28) investigated how people interact with the palpable surface and evaluated the proposed concept. Untrained participants characterized irregularities with different position, form, and hardness through palpation, and their performance was evaluated. A baseline (no irregularity) was compared to three irregularity conditions: two circular shapes with different hardness (Hard Lump and Soft Lump), and an Annulus shape. 100% of participants correctly identified an irregularity in the three irregularity conditions, whereas 78.6% correctly identified baseline. Overall agreement between participants was high (κ= 0.723). The Intersection over Union (IoU) for participants sketched outline over the actual shape was IoU Mdn = 79.3% for Soft Lump, IoU Mdn = 68.8% for Annulus, and IoU Mdn = 76.7% for Hard Lump. The distance from actual to drawn center was Mdn = 6.4 mm (Soft Lump), Mdn = 5.3 mm (Annulus), and Mdn = 7.4 mm (Hard Lump), which are small distances compared to the size of the field. The participants subjectively evaluated Soft Lump to be significantly softer than Hard Lump and Annulus. Moreover, 71% of participants thought they improved their palpation skills throughout the experiment. Together, these results show that the concept can render irregularities with different position, form, and hardness, and that users are able to locate and characterize these through palpation. Participants experienced an improvement in palpation skills throughout the experiment, which indicates the concepts feasibility as a palpation training device.

Feasibility Study and Experimental Evaluation of the Design of Nodule Prototype Developed for Palpation Display Apparatus: A Novel Device for Contactless Primary Tactile Diagnosis.

BACKGROUND: Lack of feasible palpation display for primary diagnosis of a tumor without any need of physician to patient physical contact has been reported as one of the major concerns. To further explore this area, we developed a novel palpation device consisting of a uniquely designed nodule mechanism (based on optimizing nodule top and bottom hemisphere wall thickness and manipulating granular jamming method) that can vary stiffness while maintaining the shape of the same nodule display, for which current devices are not capable of in terms of aping a tumor. METHODS: This paper evaluates the manufacturing approach of the nodule, exploring several iterations of the nodule prototype. Experiments were performed on nodule prototypes of varying wall thicknesses in order to evaluate its effect on stiffness and deformation. RESULTS AND CONCLUSIONS: Experimental results showed that nodule top and bottom wall thickness had a significant effect on the stiffness and deformation of the nodule. The higher the thickness of the top hemisphere and the lower the thickness of the bottom hemisphere, the greater the stiffness the nodule can achieve. Similarly, the display shape of the nodule can be maintained with minimal or no deformation if the nodule top hemisphere thickness is optimally higher than bottom hemisphere thickness.

Tendon-Driven Jamming Mechanism for Configurable Variable Stiffness.

Stiffness transition of a soft continuum body is an essential feature for dexterous interaction with an unstructured environment. Softness ensures safe interaction, whereas rigidness generates high force for movement or manipulation. Vacuum-based granular jamming is a widely used technique for on-line stiffness transition because of its high reconfigurability and intuitive driving method. However, vacuum driving method produces limited force levels, and the heavy weight and bulky size are unfavorable for portable applications. In this work, we propose a tendon-driven jamming mechanism for configurable variable stiffness. Compared with a vacuum system, an electric motor-tendon drive system has the benefits of force, bandwidth, size, and weight, but has different force characteristics for distribution, directionality, and transmissibility. In this study, a long snake-like shape is chosen instead of a lump shape for compatibility with tendon-drive characteristics. The snake-like shape is likely to cause buckling under the tendon force as the length increases, making the system extremely unstable. Implanting skeletal disk nodes in the structure is our solution to the buckling phenomenon by maintaining the tendon path in the desired position and for distributing the force evenly, thereby achieving stable stiffness transition capabilities for long free-curved shapes. As a proof of concept, a soft wearable device for wrist support is presented using the proposed variable stiffness mechanism. The weight of the device is 184 g, including the actuators, and it can support 2 kgf. Furthermore, the stiffness transition is completed within 2 s, thus achieving quick responses.

A multi-subject accuracy study on granular jamming for non-invasive attachment of fiducial markers to patients.

PURPOSE: This short communication describes experimental evaluation of a new granular jamming cap (GJC) recently introduced in Wellborn et al. (Int J Comput Assist Radiol Surg 12(6):1069-1077, 2017). The contributions beyond [8] are (1) to evaluate accuracy across multiple human subjects, and (2) to determine how much of the accuracy improvement is attributable to improved fiducial marker arrangement alone, and how much is due to granular jamming. The motivation for this GJC is to improve the accuracy of image-guidance interfaces in transnasal skull base surgery. Accuracy depends on a rigid connection between tracked fiducial markers and the patient. By molding itself to the unique contours of the individual patient's head and then solidifying, the GJC can firmly attach fiducial markers to a patient, increasing accuracy in the presence of disturbances. METHODS: A multi-subject study ([Formula: see text]) was performed to evaluate the accuracy of the GJC compared to a clinically used headband-based fixation device, in the presence of simulated accidental bumping (light force and impact events) that could occur in a real-world operating room. RESULTS: The GJC reduced the average target registration error at the pituitary gland by 66% in our force experiments and 78% in our impact experiments, which were statistically significant reductions ([Formula: see text]). Maximum target registration error was similarly reduced by 55% and 78% in the same two perturbation tests. CONCLUSION: The GJC increases the accuracy of transnasal image-guidance under force and impact perturbations by more firmly, yet non-invasively, attaching fiducial markers to the patient. We find that granular jamming provides accuracy improvement beyond that associated with improved fiducial marker arrangement.

Chain-Like Granular Jamming: A Novel Stiffness-Programmable Mechanism for Soft Robotics.

The ability to regulate the mechanical stiffness in a large range could be extremely important for soft robots to interact with the environment more effectively. In this article, we propose a novel chain-like granular jamming mechanism to achieve a large range of stiffness variation instantly, based on a method that is totally different from existing vacuum-based granular jamming systems. Theoretical modeling is introduced to find the best combination of granules to form the chain-like structure (CLS) and experiments are conducted to demonstrate it. The experimental results indicate that the novel jamming structure is able to achieve a stiffness variation range as large as 50.7 folds. To further validate the effectiveness of the CLS, a soft-rigid hybrid actuator based on the jamming structure is proposed and an integrated fabrication method is provided. Furthermore, an anthropomorphic hand based on the hybrid actuators is developed and the experimental results show that the hand is not only versatile enough to manipulate various objects with different weights, material properties, shapes, and surface characteristics at the soft state, like existing soft grippers, but also can lift heavy objects (1.5 kg in a cylindrical grasping gesture and 3.52 kg in a hook gesture) at the rigid state, which could be difficult for other soft grippers. Finally, the hand is integrated into our homemade service robot, significantly improving the practicability and safety of the robot when serving humans.

A Soft Retraction System for Surgery Based on Ferromagnetic Materials and Granular Jamming.

In recent years, minimally invasive surgery (MIS) has gained wider acceptance among surgeons. MIS requires high skills for the operators, mainly due to its intrinsic technical limitations. Tissue manipulation and retraction remain the most challenging tasks; more specifically liver, stomach, and intestine are the organs mostly involved in retraction tasks for abdominal procedures. The literature reports an increasing interest toward dedicated solutions for abdominal tissue retraction tasks. To overcome the limitations of commercial systems and research prototypes, the aim of this study is the design, the realization, and the validation of a retraction system that is simple, reliable, easy to use, safe, and broadly compatible with MIS. The proposed retractor has two main components: (1) a soft central part with variable stiffness obtained by exploiting the granular jamming phenomenon for assuring, at the same time, safe introduction into the abdominal cavity and stable retraction and (2) two iron cylinders located at the two extremities of the device for anchoring the retractor to the abdominal wall by using the magnetic attraction force between these components and two external permanent magnets. System design has been performed by deeply investigating granular jamming principle and ferromagnetic properties of iron elements. Ex vivo and in vivo assessment has been carried out with the final aim to identify the most appropriate design of each retractor component and to demonstrate the advantages of using a soft system with variable stiffness during a retraction task.

Toward a Flexible Variable Stiffness Endoport for Single-Site Partial Nephrectomy.

Laparoscopic partial nephrectomy for localized renal tumors is an upcoming standard minimally invasive surgical procedure. However, a single-site laparoscopic approach would be even more preferable in terms of invasiveness. While the manual approach offers rigid curved tools, robotic single-site systems provide high degrees of freedom manipulators. However, they either provide only a straight deployment port, lack of instrument integration, or cannot be reconfigured. Therefore, the current main shortcomings of single-site surgery approaches include limited tool dexterity, visualization, and intuitive use by the surgeons. For partial nephrectomy in particular, the accessibility of the tumors remains limited and requires invasive kidney mobilization (separation of the kidney from the surrounding tissue), resulting in patient stress and prolonged surgery. We address these limitations by introducing a flexible, robotic, variable stiffness port with several working channels, which consists of a two-segment tendon-driven continuum robot with integrated granular and layer jamming for stabilizing the pose and shape. We investigate biocompatible granules for granular jamming and demonstrate the stiffening capabilities in terms of pose and shape accuracy with experimental evaluations. Additionally, we conduct in vitro experiments on a phantom and prove that the visualization of tumors at various sites is increased up to 38% in comparison to straight endoscopes.

Coffee: the key to safer image-guided surgery-a granular jamming cap for non-invasive, rigid fixation of fiducial markers to the patient.

PURPOSE: Accurate image guidance requires a rigid connection between tracked fiducial markers and the patient, which cannot be guaranteed by current non-invasive attachment techniques. We propose a new granular jamming approach to firmly, yet non-invasively, connect fiducials to the patient. METHODS: Our granular jamming cap surrounds the head and conforms to the contours of the patient's skull. When a vacuum is drawn, the device solidifies in a manner conceptually like a vacuum-packed bag of ground coffee, providing a rigid structure that can firmly hold fiducial markers to the patient's skull. By using the new Polaris Krios optical tracker, we can also use more fiducials in advantageous configurations to reduce registration error. RESULTS: We tested our new approach against a clinically used headband-based fiducial fixation device under perturbations that could reasonably be expected to occur in a real-world operating room. In bump testing, we found that the granular jamming cap reduced average TRE at the skull base from 2.29 to 0.56 mm and maximum TRE at the same point from 7.65 to 1.30 mm. Clinically significant TRE reductions were also observed in head repositioning and static force testing experiments. CONCLUSION: The granular jamming cap concept increases the robustness and accuracy of image-guided sinus and skull base surgery by more firmly attaching fiducial markers to the patient's skull.