Ultraviolet light-responsive photorheological fluids: as a new class of smart fluids

Abstract

We present a comprehensive introduction to the photorheological (PR) fluids whose rheological behavior can be changed by ultraviolet (UV) light with a wavelength of 365 nm. When the PR fluid was exposed to UV light, the viscosity of the fluid decreased, while the viscosity recovered to its initial value when UV light was turned off, indicating that the viscosity of these types of fluids can be reversible and tunable by UV light. Contrary to conventional smart fluids, such as electrorheological and magnetorheological fluids, PR fluid does not suffer from a phase splitting problem because it exists in a single-phase solution. Additionally, the PR fluid does not require any contact component, such as electrodes, and electric wires that are essential components for conventional smart fluids. In this work, the PR fluids were synthesized by doping lecithin/sodium deoxycholate reverse micelles with a photo-chromic spiropyran compound. It is demonstrated that the viscosity changes of PR fluids can be induced by UV light, and their rheological properties are examined in detail. In addition, an example of tailoring rheological properties using photoluminescence was introduced for improved response time. One of the potential applications, such as microfluidic flow control using the PR fluids, is also briefly presented.

Cellulose-Based Smart Fluids under Applied Electric Fields

“…In contrast, ER fluids that have the opposite behavior (i.e., those that show decreased shear stress and viscosity under an applied electrical field) are called negative ER fluids [ 74 , 75 , 76 , 77 ]. However, the characteristics of both types of ER fluids can be improved through light lamination; these are called photo-electrorheological (photo ER) fluids [ 78 , 79 ]. Photogenerated carriers are considered to be responsible for changing the electric properties of the positive or negative materials and enhancing their ER phenomena.…”

Dual Response of Materials under Electric and Magnetic Fields

“…When the viscosity of UPPG is higher than viscosity of PDMS, ER effect of the suspension is positive. When the viscosity of UPPG is lower than viscosity of PDMS, the ER effect of the suspension is negative [42].…”

Photo-Rheological Fluid-Based Colorimetric Ultraviolet Light Intensity Sensor

“…These fluids have attracted increased attention since Lee et al reported that they can be easily synthesized in the laboratory using commercially available chemicals and ingredients, such as spiropyran, instead of using conventional ingredients, such as trans-ortho-methoxycinnamic acid, alpha-cyclodextrin, and hydroxyethyl cellulose [ 1 , 2 , 3 , 4 ]. PR fluids are characterized by changes in their properties such as color and viscosity when irradiated by the UV light [ 5 ]. A study by Cho et al demonstrated the possibility of implementing damper and flow valves based on the principle of viscosity changes of PR fluids [ 5 , 6 ].…”

“…PR fluids are characterized by changes in their properties such as color and viscosity when irradiated by the UV light [ 5 ]. A study by Cho et al demonstrated the possibility of implementing damper and flow valves based on the principle of viscosity changes of PR fluids [ 5 , 6 ]. Meanwhile, Jin et al experimented with PR fluids to verify the dual-response characteristic evoked by UV light and temperature [ 7 ].…”