Pine cone scale-inspired motile origami

Abstract

Stimuli-sensitive hydrogels have received attention because of their potential applications in various fields. Stimuli-directed motion offers many practical applications, such as in drug delivery systems and actuators. Directed motion of asymmetric hydrogels has long been designed; however, few studies have investigated the motion control of symmetric hydrogels. We designed a pine cone scale-inspired movable temperature-sensitive symmetric hydrogel that contains Fe 3 O 4 . Alignment of Fe 3 O 4 along the magnetic force is key in motion control in which Fe 3 O 4 acts like fibers in a pine cone scale. Although a homogeneous temperature-sensitive hydrogel cannot respond to a temperature gradient, the Fe 3 O 4 -containing hydrogel demonstrates considerable bending motion. Varying degrees and directions of motion are easily facilitated by controlling the amount and alignment angle of the Fe 3 O 4 . The shape of the hydrogel layer also influences the morphological structure. This study introduced facile and low-cost methods to control various bending motions. These results can be applied to many fields of engineering, including industrial engineering. NPG Asia Materials (2017) 9, e389; doi:10.1038/am.2017.79; published online 16 June 2017 INTRODUCTION Stimuli-responsive hydrogels have received considerable attention in recent decades because of their potential application in the development of multifunctional devices. Various types of stimuli-responsive hydrogels with applications in engineering have been introduced 1-7 . Stimuliresponsive hydrogels can change their shape, surface characteristics, solubility and form. These hydrogels have been used in various practical applications such as in drug delivery systems, cell culture, sensors, pumps and actuators 7-11 . They have been elaborately developed using various fabrication methods to broaden their applications 12,13 .One of the most important advancements in this field is the application of stimuli-responsive hydrogels in motion control in smart functional materials. Stimuli-responsive hydrogels have typically been utilized for motion control, especially in actuators [14][15][16][17][18][19][20] . Motion control is also important in many microscale engineering applications such as flow control in micro-fluidic devices and design of micro actuators 14,21,22 . The shape transformation of soft materials also has potential applications in tissue engineering 23 : differential swelling or shrinkage creates internal stresses in the composite hydrogel sheet and transforms its shape in a specific manner. Biocompatible bilayer structures are used to fabricate tunable micro-capsules applied as robust micro-carriers 24 . Controlled motion of functional materials has various technical applications. Most developed movable hydrogels have anisotropic structures. A typical method of inducing motion is the combination of two different materials into a bilayer structure [25][26][27][28][29] . Owing to the varying volume changes of the two materials, the bilayer exhibits bending/unben...

Functional Principles of Morphological and Anatomical Structures in Pinecones

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Possibility of realizing quantum spin Hall effect at room temperature instanene/Al2O3(0001)

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Fe3O4–Silicone Mixture as Flexible Actuator

“…Additionally, it can be utilized in industrial fields including robot manipulators and weighting machines. In addition, as iron oxide is mixed, it can be used for developing actuators stimulated by both electric and magnetic fields [ 32 ].…”