Human‐Iris‐Like Aperture and Sphincter Muscle Comprising Hyperelastic Composite Hydrogels Containing Graphene Oxide

Abstract

Soft hydrogels are extensively studied for developing human‐body‐mimicking actuators because of their stimuli‐responsive volume change and elasticity. Mimicking a human eye with hydrogels is very challenging because both the large variation in the volume and the high modulus of the gels should be concurrently achieved. In the human eye, adjusting the iris for controlling the focal point and light transmittance is achieved by the contraction of the sphincter muscle. In this work, a hyperelastic poly(N‐isopropylacrylamide) containing graphene oxide (PNIPAm/GO) composite hydrogels, which exhibits a thermo‐responsive volume phase transition is developed. The fact that the inner hole size for center‐cut hydrogels can increase or decrease during heating depending on the geometry of the hydrogels is revealed. Based on these findings, human‐iris‐like actuators capable of controlling the shape of a polydimethylsiloxane (PDMS) lens for adjusting magnification of an object is developed. When heated, the hyperelastic hydrogels act like the sphincter muscle in the eye, inducing the curvature change of the attached PDMS lens. Thus, hyperelastic hydrogels of large variation can provide an efficient platform to fabricate various soft actuation systems.

Evolution of natural eyes and biomimetic imaging devices for effective image acquisition

“…5a). 108 The hydrogel exhibits significant volume variation, which enables the actuator to function similarly to the human iris. When the hemispherical hydrogel iris is exposed to light, the size of the internal hole decreases, reducing the amount of light heading to the photodiode; however, when the light is turned off, the photocurrent increases according to the increased amount of light due to the volume recovery of PNIPAm/GO.…”

A dual stimuli-responsive smart soft carrier using multi-material 4D printing

“…It is known that the area change of the slot is larger than that of the circular slot because the hoop stress can be minimized if the leg exists in the slot. 38 Therefore, a leg-shaped slot was selected, and the area change rate of the slot according to the number of legs was measured. The 2, 3, and 4 leg slots were designed to have an identical length (2.7 mm) and width (0.5 mm).…”

Smart Hydrogels Meet Carbon Nanomaterials for New Frontiers in Medicine

“…This actuator was designed to mimic the human iris’ action in response to light. Upon illumination, the photo-thermal conversion effect of GO led to a decrease in size of the inner hole, with a consequent decrease in transmitted light as the incident light intensity increased [ 118 ]. Methacrylate hydrogels have also been proposed as components to attain lenses, and polyvinylpyrrolidone and GO nanoparticles demonstrated high wettability as additives, allowing also for an ultraviolet shielding effect [ 119 ].…”