A Shape Memory Polymer Adhesive Gripper For Pick-and-Place Applications

Abstract

Over the past few years, shape memory polymers (SMPs) have been extensively studied in term of their remarkable reversible dry adhesive properties and related smart adhesive applications. However, these exceptional properties of SMPs have not been exploited for pickand-place applications, which would otherwise advance the robotic manipulation. This work explores the use of SMPs to design an adhesive gripper which pick and place target solid objects relying on reversible dry adhesion of SMP. Compared with common finger or soft grippers, the SMP adhesive gripper interacts with a single surface of a target object for pick-and-place. Furthermore, it is easy and inexpensive to manufacture and applicable to various surfaces since it involves reversible dry adhesion. In this paper, associated physical mechanisms and temperature analyses are studied and conducted. Also, the study includes manufacturing of a dual SMP and a release tip which substantially enhances the adhesion strength and considerably minimizes the releasing force. Finally, the versatility and utility of the SMP adhesive gripper are demonstrated through pick-and-place experiments.

Dual Adaptation of a Flexible Shape Memory Polymer Adhesive

“…1 To achieve both large-area conformal contact and low compliance, consequently high dry adhesion, the rubbery-state SMP is specially cooled down to the glassy state with maintaining its original area of conformal contact. Until now, these properties of SMPs have enabled high-strength, reversible, and reusable dry adhesives 40,41 even working in underwater environments. 42 However, those SMP dry adhesives are not capable of maintaining the strong adhesion to flexible adherends since those adhesives are in the rigid glassy state when adhering.…”

“…This shape memory effect of many reported SMPs is thermally triggered but some of the athermal stimuli-triggered SMPs have also been reported, such as electro, − magnetic, − water, , or photoactive , SMP composites. These unique material properties allow SMPs to be utilized in a various range of applications encompassing biomedical devices, , mechanical components, , temperature sensors, MEMS applications, − transfer printing, ,, droplet manipulating, − and robotic grippers. − Many of these applications employ the strain energy of SMPs in the way of accumulating energy in the temporary shape and releasing it by applying external stimuli. Designing a high-strength dry adhesive is another example of exploiting SMPs.…”

“…However, once the SMP is heated over the glass-transition temperature ( T g ), the storage modulus drops drastically and the SMP becomes a “rubbery” state. In this rubbery state, the SMP can make a conformal contact with a smooth or a moderately rough surface and maximizes the effective area of contact that creates van der Waals forces. Nevertheless, at this rubbery state, the compliance of the SMP is high such that it adversely affects the overall adhesion force .…”

Tunable Adhesion of Shape Memory Polymer Dry Adhesive Soft Robotic Gripper via Stiffness Control

“…In this work, a more sophisticated SMP dry adhesive gripper based on pure Van der Waals force on an adhesive contact area is presented, and its strong, material-independent, and reversible adhesion is demonstrated for picking flat, smooth, or moderately rough objects. [48] Furthermore, because an SMP's dry adhesion is water-resistant, the SMP adhesive gripper can be used on wet or submerged objects [49]. A thermoresponsive SMP is used here, and it has the ability to stably fix to its deformed or 'temporary' shape when heated, deformed, and cooled.…”