Motion of Polymer Gels by Spreading Organic Fluid on Water

Abstract

We have constructed a new class of polymer gel that undergoes translational and rotational motions in water. These polymer gels consist of cross-linked hydrophobic-hydrophilic copolymers, which swell in watermiscible organic fluid but collapse in water. When these gels swollen in organic solvent are placed on supporting water, they start to do motion. The mode of motion depends on the shape of the gel: a disk-or spherical shaped gel exhibits translational motion while a triangular or a cubic one exhibits rotation. The velocity and duration of gel motion are strongly associated with its size and chemical structure. The driving force of the motion is originated from the surface spreading of organic solvent, which is pumped out of the gel because of the high osmotic pressure and hydrostatic pressure in the gel.

Maze solving using temperature-induced Marangoni flow

“…It should be noted that the gradient of the surface tension to propel particles has been used in several cases. [33][34][35] Even the camphor boats represent similar system. 36,37 In these systems, the motion of particles is governed by a local gradient of the surface tension created by a chemical entity (e.g., polymer gel, camphor particles) emitting surface active substances, thus changing locally the surface tension near the chemical object at the liquid-air interface.…”

Effect of Asymmetry on Adhesion and Locomotion of Soft-Bodied Objects

“…(b) A series of images that represents the motion of polymer gel is induced by external electric field [9]. (c) Motion of PSA gels: translational motion of a disk-shaped gel is induced by spreading of organic solvent on water [18] (Reprinted from Refs. [9,15,18] with permission) Fig.…”

“…(c) Motion of PSA gels: translational motion of a disk-shaped gel is induced by spreading of organic solvent on water [18] (Reprinted from Refs. [9,15,18] with permission) Fig. 2 A series of images represents (a) motion of polyacrylamide hydrogel cylinder on a thin elastomeric film of polydimethysiloxane, which is subject to vibration.…”

“…Large difference in pressure between inside and outside of the gel ejects the organic solvent out of the gel which imparts reactive thrust on it making it to move forward ( Fig. 1c) [18].…”

“…Since then, many approaches to create chemomechanical motion are currently being investigated, several of them being specifically based on soft material. These materials are capable of deforming their shape by external stimuli such as electric field [9,12], temperature [13,14], photo [15,16], pH [17], and solvent [18].…”