Microwedge Machining for the Manufacture of Directional Dry Adhesives

Abstract-Grasping objects that are too large to envelop is traditionally achieved using friction that is activated by squeezing. We present a family of shear-activated grippers that can grasp such objects without the need to squeeze. When a shear force is applied to the gecko-inspired material in our grippers, adhesion is turned on; this adhesion in turn results in adhesion-controlled friction, a friction force that depends on adhesion rather than a squeezing normal force. Removal of the shear force eliminates adhesion, allowing easy release of an object. A compliant shearactivated gripper without active sensing and control can use the same light touch to lift objects that are soft, brittle, fragile, light, or very heavy. We present three grippers, the first two designed for curved objects, and the third for nearly any shape. Simple models describe the grasping process, and empirical results verify the models. The grippers are demonstrated on objects with a variety of shapes, materials, sizes, and weights.

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“…Details of manufacturing are found in [18], [19]. B) The tips of the microwedge adhesive self-engage with a surface when brought in contact.…”

Section: Fig 2 A)mentioning

confidence: 99%

Grasping Without Squeezing: Design and Modeling of Shear-Activated Grippers

et al. 2018

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“…positioning stage and a six-axis force-torque transducer, using methods described in [9]. This limit curve is plotted in Fig.…”

Section: A Collapsing Truss Grasper: Limit Curvesmentioning

confidence: 99%

“…This produces a 300-400 µm thick film with an array of 80 µm tall angled micro-wedges. A thin, smooth PDMS film is then deposited on the tips of the features through a post-treatment process involving dipping them into uncured PDMS and then pressing them against a wafer [9], causing a change in shape and surface smoothness on the engaging surfaces. After post-treatment, the back side of the film is glued to a fiberglass sheet using RTV silicone adhesive (Smooth-On Sil-Poxy), and the fiberglass sheet is then cut into tiles using a laser cutter.…”

Section: B Collapsing Truss Grasper: Adhesive Loadingmentioning

confidence: 99%

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Dynamic surface grasping with directional adhesion

Hawkes

Christensen

Eason

et al. 2013

2013 IEEE/RSJ International Conference on Intelligent Robots and Systems

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Dynamic surface grasping is applicable to landing of micro air vehicles (MAVs) and to grappling objects in space. In both applications, the grasper must absorb the kinetic energy of a moving object and provide secure attachment to a surface using, for example, gecko-inspired directional adhesives. Functional principles of dynamic surface grasping are presented, and two prototype grasper designs are discussed. Computer simulation and physical testing confirms the expected relationships concerning (i) the alignment of the grasper at initial contact, (ii) the absorption of energy during collision and rebound, and (iii) the force limits of synthetic directional adhesives.

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“…Computerized numerical control (CNC) milling and micromachining has been widely used to fabricate lab-on-a-chip devices, [26,27] PDMS microstructures and adhesives, [28,29] and even pneumatic logic circuits. [30] In this work, a milling process to cast a conductive elastomer, carbon nanotube (CNT)/PDMS, was developed to achieve microscale features over a large area, Figure 3.…”

Section: Doi: 101002/admt201600188mentioning

confidence: 99%

Rapid Manufacturing of Mechanoreceptive Skins for Slip Detection in Robotic Grasping

Charalambides

Bergbreiter

2016

Adv Materials Technologies

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results in laborious and complicated multilayer assembly with sub-Newton force ranges. [12] MEMS manufacturing also limits the sensing area to that of a silicon wafer. [13] Other tactile sensors which have large sensing areas have been limited to normal force sensing only, [14,15] or have had limited flexibility. [16] Microfluidic eutectic indium gallium tactile sensors have achieved remarkable flexibility but are potentially hazardous if ruptured. [17] Therefore, there is a need for a flexible, large area tactile sensor array capable of shear force sensing in addition to normal force sensing.The transduction method also plays an important role in the design and performance of tactile sensors. Flexible tactile sensor arrays typically utilize parallel-plate style capacitors, [18] or resistive serpentines or strips to detect applied loads. [19] Elastomer-based piezoresistive sensors tend to suffer from electromechanical hysteresis, [20,21] while capacitive sensors require significant efforts in shielding. [11,22] Thus, an alternate sensing modality was needed to be more practical in the field.In this work, two transduction methods (contact resistance and capacitive) were explored, Figure 1. A contact resistance sensing technique is proposed to simplify electronics, avoid the need for capacitive shielding, and minimize electromechanical hysteresis at the expense of DR. Two conductive features, referred to as the "pillar" and "pad", come into physical contact as loads are applied. As a normal force is applied, the pillar and pads flatten and expand through the Poisson effect, and come into contact causing a uniform decrease in contact resistance on each side. Meanwhile, a shear force results in a differential contact resistance; contact resistance decreases in the direction of shear and increases on the opposite side.In the capacitive sensing approach, the sensor is encapsulated with a dielectric to form a capacitor between the pillar and pad. As a normal force is applied, the sensor flattens and expands through the Poisson effect, the capacitor gap increases, and the capacitance decreases on each side uniformly. Meanwhile, a shear force results in an increase in capacitance in the direction of loading, and a decrease in capacitance on the opposite side. Capacitive transduction was explored by the authors in previous work, but was revisited since taller features enabled by the manufacturing process presented in this paper can improve sensor sensitivity over prior work. [11] However, the capacitive shielding required to make these sensors useful in a wide range of applications was not a focus of this work.In order to achieve a flexible sensing skin, soft elastomers were the preferred material of choice. [2] Elastomers, such as polydimethylsiloxane (PDMS), are especially favorable for these architectures since they are incompressible (Poisson's ratio near 0.5), which maximizes lateral expansion under normal deformation. The contact resistance approach differs from previous contact resistance work in that the sensor cir...

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Microwedge Machining for the Manufacture of Directional Dry Adhesives

Cited by 93 publications

References 38 publications

Grasping Without Squeezing: Design and Modeling of Shear-Activated Grippers

Grasping Without Squeezing: Design and Modeling of Shear-Activated Grippers

Dynamic surface grasping with directional adhesion

Rapid Manufacturing of Mechanoreceptive Skins for Slip Detection in Robotic Grasping

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