Paper Robotics: Self‐Folding, Gripping, and Locomotion

Abstract

a century, sensational engineering efforts have been performed to develop new synthetic materials, and intensive studies of forces needed to deform those soft materials have examined the use of pneumatic, thermal, electrical, and chemical energy. [11][12][13] The second research stream designs low-profile, sheet-like robots, named "robotic origamis" (or "robogamis") that offer softness and reconfigurability with multiple bending degrees of freedom. [8][9][10] In robogamis, the rigid sheets are connected through soft joints, where 2D patterns can be folded into 3D structures by low profile actuations such as electrostatic forces, shape memory alloys, and pneumatic pressures. [2] Such robogamis can autonomously transform themselves into programmed shapes and perform complex tasks in unpredictable environments. Substantial progress in soft material research has produced achievements that are critical in terms of robogami techniques [2] while soft robotics and origami folding concepts have opened new applications. [9] However, soft robotics and robogamis have historically developed separately, and studies on robogamis with soft matter were unavailable or quite limited even though their integration is expected to generate substantial achievements in terms of cost, fabrication, operation, and performance. Built-in folds made of soft materials have the considerable potential to yield continuum, compliant, and configurable properties for robots.In this work, we introduce a new approach to combine these two robotic techniques by using soft paper substrates and a waterresponsive origami technique. The capillary action of sprayed water molecules is constrained by hydrophilic channels on paper, whose number and size are carefully defined by double-sided printing and the asymmetrical penetration of wax. In particular, a bilayered single sheet of paper that uses wax and water can lead to programmed deformations from different swelling and shrinking properties of the layers. A wax-water pattern on paper develops a folding actuation with a specific degree and shape and unfolding with evaporation without being mechanically manipulated by external forces or moments. The 2D sheet of paper can be controllably self-folded into various 3D structures, demonstrating self-folding actuation, low-weight object manipulation, and biomimetic locomotion through bending and relaxation. Although a couple of paper-based robotic concepts were partly proposed before, [14,15] no technique has yet emerged as a simple print-and-fold actuator powered by environmental humidity or water for comprehensive robotic functions including self-folding, Soft robotics driven by origami can fundamentally advance robotic functionalities by significantly improving continuum, compliance, and configurability. Here, a new field is proposed, "paper robotics," which is based on moistureresponsive self-folding of paper substrates into functional 3D machines using origami-inspired techniques. By properly designing a hydrophobic wax layer and a hygro-expandable hydrophilic ...

Cellulose‐Based Soft Actuators

“…For instance, Ryu et al reported an omega-shaped aquatic insect robot by using soft paper substrates and a water-responsive origami technique. [126] The device can float on the surface of water and be triggered by the sprayingevaporating cycles of water, then a forward locomotion with a theoretical speed of 10.9 mm s −1 was achieved.…”

Current Development on Origami/Kirigami‐Inspired Structure of Creased Patterns toward Robotics

“…As shown in Figure 5E, the multiple-base-shape creased kirigami structures are frequently related to self-folding [122,[124][125][126][127][128][129][130][131][132][133] and the concepts of 4D printing, which usually consists of several basic geometries adjacent to each other and would be "clutched" to a designed 3D structure through preprocessing [134] and external stimulation or guiding. [4,5] These structures have attracted large amounts of attention because they are easily designable, low-cost, less time-consuming for fabrication, have a low rate of waste production, and are suitable for volume production.…”

Origami-inspired folding assembly of dielectric elastomers for programmable soft robots

“…Scientists have developed different types of origami-inspired soft robots with a variety of materials and actuation methods, each with specific mechanical manipulation functions and movement styles 20 . For instance, a battery-free miniature origami robotic arm based on origami actuation was developed with shape memory alloys and has been used for arm orientation control and object grasping 21 .…”