PH-sensitive hydrogel-based valves: A transient fully-coupled fluid-solid interaction study

Abstract

pH-sensitive hydrogels are promising materials to be employed in microfluidic devices, especially microvalves. In this paper, a theory of transient swelling of pH-sensitive micro-valve is presented. A transient constitutive model that captures electrical, chemical, and mechanical fields is considered to model the swelling phenomenon. The diffusion of ions into the hydrogel, the electromigration, and convection are described by implementing the Nernst-Planck equation. Assuming Gent model, hydrogel is considered as a compressible hyperelastic material and osmotic pressure is assumed as an external loading. Due to benefits of in-plane valves, a design of the micro-valve is studied. Design simplicity and great sealing are vital factors which can be considered as an advantage of this valve for fabrication. This design and modeling approach has not been used for pH-sensitive hydrogels in earlier works. Thus, we have studied the transient swelling of pH-sensitive hydrogel microvalve, when effects of fluid-structure-interaction are examined on valve performance. It is noted that in most previous studies, equilibrium conditions have been assumed. While considering transient fully-coupled fluid-structure-interaction is necessary to capture a more realistic modeling. The results illustrate that the microvalve blocks the channel much earlier than reaching the equilibrium-state, which implies importance of the transient behavior of hydrogels.

Effect of sodium chloride on the enhanced performance of chitosan-based ion actuator

“…In recent years, the researchers found that the actuate membrane materials including sodium alginate [8] , cellulose, chitosan [9][10][11][12] . Due to their unique three-dimensional network structure and ability to retain a large amount of water, ion actuator had a wide range of applications in hydrogel arti cial muscles [13] including biomedical applications, drug carriers [14][15] , biosensors [16] , medical devices [17] , tissue engineering [18] , separation systems [19][20] , micro uidic systems [21] , microvalves [22] and actuator [23][24] . Chitosan (CS) was a product of natural chitin.…”

Programmable self-folding of trilayer and bilayer-hinge structures by time-dependent swelling of tough hydrogels

“…Due to the swelling and de-swelling of hydrogels, these materials undergo considerable volume change under a change in external stimuli, including temperature, pH, light intensity, ion concentration, electric and magnetic fields (Kasinathan and Srinivasan, 2018;Shojaeifard and Baghani, 2019;Shojaeifard et al, 2019aShojaeifard et al, , 2019bShojaeifard et al, , 2021. Although conventional hydrogels have various merits to be utilized in diverse applications (Bin et al, 2021;Guenther et al, 2009;Niroumandi et al, 2021bNiroumandi et al, , 2022, the composition of inhomogeneous networks and low polymer content make the hydrogels mechanically weak. Moreover, regarding the enthusiasm for finding alternatives for living tissue, researchers seek a biocompatible material that can absorb water and possess high toughness and shock absorption.…”