Advances in soft robotics, materials science, and stretchable electronics have enabled rapid progress in soft grippers. Here, a critical overview of soft robotic grippers is presented, covering different material sets, physical principles, and device architectures. Soft gripping can be categorized into three technologies, enabling grasping by: a) actuation, b) controlled stiffness, and c) controlled adhesion. A comprehensive review of each type is presented. Compared to rigid grippers, end-effectors fabricated from flexible and soft components can often grasp or manipulate a larger variety of objects. Such grippers are an example of morphological computation, where control complexity is greatly reduced by material softness and mechanical compliance. Advanced materials and soft components, in particular silicone elastomers, shape memory materials, and active polymers and gels, are increasingly investigated for the design of lighter, simpler, and more universal grippers, using the inherent functionality of the materials. Embedding stretchable distributed sensors in or on soft grippers greatly enhances the ways in which the grippers interact with objects. Challenges for soft grippers include miniaturization, robustness, speed, integration of sensing, and control. Improved materials, processing methods, and sensing play an important role in future research.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/adma.201707035

Soft Robotic Grippers.

This article gives an overview of research performed in the field of haptic information feedback during minimally invasive surgery (MIS). Literature has been consulted from 1985 to present. The studies show that currently, haptic information feedback is rare, but promising, in MIS. Surgeons benefit from additional feedback about force information. When it comes to grasping forces and perceiving slip, little is known about the advantages additional haptic information can give to prevent tissue trauma during manipulation. Improvement of haptic perception through augmented haptic information feedback in MIS might be promising.

Haptics in minimally invasive surgery – a review

Shape and topology optimization of compliant mechanisms using a parameterization level set method

A parameterization level set method is presented for structural shape and topology optimization of compliant mechanisms involving large displacements. A level set model is established mathematically as the Hamilton-Jacobi equation to capture the motion of the free boundary of a continuum structure. The structural design boundary is thus described implicitly as the zero level set of a level set scalar function of higher dimension. The radial basis function with compact support is then applied to interpolate the level set function, leading to a relaxation and separation of the temporal and spatial discretizations related to the original partial differential equation. In doing so, the more difficult shape and topology optimization problem is now fully parameterized into a relatively easier size optimization of generalized expansion coefficients. As a result, the optimization is changed into a numerical process of implementing a series of motions of the implicit level set function via an existing efficient convex programming method. With the concept of the shape derivative, the geometrical non-linearity is included in the rigorous design sensitivity analysis to appropriately capture the large displacements of compliant mechanisms. Several numerical benchmark examples illustrate the effectiveness of the present level set method, in particular, its capability of generating new holes inside the material domain. The proposed method not only retains the favorable features of the implicit free boundary representation but also overcomes several unfavorable numerical considerations relevant to the explicit scheme, the reinitialization procedure, and the velocity extension algorithm in the conventional level set method.

A level set method for shape and topology optimization of large‐displacement compliant mechanisms

The end-effectors in the state-of-the-art robotic tools for minimally invasive surgery (MIS) are actuated by actuator packs located outside the patient's body, with the power transmitted from the actuator pack to the end-effector by means of sliding link or tendon-driven mechanisms. This method of power transmission limits the number of degrees-of-freedom (DOFs) in these systems, as the design of a spherical wrist gets complicated. The design of the spherical wrists can be simplified, and the number of DOFs increased, if local actuation is used for the end-effector. However, there are no suitable actuation systems available in the literature. In this paper, a novel design idea for developing a millimeter-scale actuator is presented for locally actuating the end-effector (5-mm-diameter laparoscopic needle driver) for a robot performing MIS. This actuator is designed by combining a dc micromotor and a shape memory alloy actuator in series. The designed actuator is 5.14 mm in diameter (including casing) and 40 mm in length, and is used to actuate a 20-mm-long needle driver assembly, while generating a force of 24 N, resulting in a gripping force of 8 N. The total stroke length of the actuator is 1 mm, which results in a 45 opening of the needle driver jaw with a gap of 8 mm in between the jaws.

Design and Characterization of a Novel Hybrid Actuator Using Shape Memory Alloy and DC Micromotor for Minimally Invasive Surgery Applications

This paper introduces the benefits of exploiting elasticity in the engineering design of surgical tools, in general, and of minimally invasive procedures, in particular. Compliant mechanisms are jointless mechanisms that rely on elastic deformation to transmit forces and motion. The lack of traditional joints in these single-piece flexible structures offers many benefits, including the absence of wear debris, pinch points, crevices, and lubrication. Such systems are particularly amenable to embedded sensing for haptic feedback and embedded actuation with active-material actuators. The paper provides an overview of design synthesis methods developed at the Compliant Systems Design Laboratory and focuses specifically on surgical applications. Compliant systems have potential to integrate. well within the constraints of laparoscopic procedures and telerobotic surgery. A load-path representation is used within a genetic algorithm to solve two gripper example problems. In addition, the paper illustrates the design and construction of an organ (kidney) manipulator for use in minimally invasive procedures.

Z. Kreiner

Papers

Design and Application of Compliant Mechanisms for Surgical Tools