Biocatalytic Feedback‐Controlled Non‐Newtonian Fluids

Abstract

Non‐Newtonian fluids are ubiquitous in daily life and industrial applications. Herein, we report an intelligent fluidic system integrating two distinct non‐Newtonian rheological properties mediated by an autocatalytic enzyme reaction. Associative polyelectrolytes bearing a small amount of ionic and alkyl groups are engineered: by carefully balancing the charge density and the hydrophobic effect, the polymer solutions demonstrate a unique shear thickening property at low pH while shear thinning at high pH. The urea‐urease clock reaction is utilized to program a feedback‐induced pH change, leading to a strong upturn of the nonlinear viscoelastic properties. As long as the chemical fuel is supplied, two distinct non‐Newtonian states can be achieved with a tunable lifetime span. As a proof of concept, we demonstrate how the physical energy‐driven nonequilibrium properties can be manipulated by a chemical‐fueled process.

Programming properties of transient hydrogels by an enzymatic reaction

“…To induce a pH change, the autocatalytic reaction between urea and urease was developed by Taylor et al [55][56][57] and also used by Walther et al 58,59 and other research groups. 16,[60][61][62][63] Under aqueous conditions, urea reacts with urease to produce ammonia, which is responsible for the increase of the pH of the medium. [64][65][66][67][68] The reaction itself is highly dependent on the initial reaction conditions such as pH and the reagent concentrations, 57,64,65 which enables us to exercise precise control over the rate of pH change and subsequent transitions between the energy states.…”

Out‐of‐equilibrium supramolecular self‐assembling systems driven by chemical fuel

“…Reproduced with permission. [91] Copyright 2020, Wiley-VCH. (E) Transient crystallization of a cucurbit [8]uril-based supramolecular self-assembling system driven by TCA.…”

“…Additionally, a non-Newtonian polymeric fluid system with a switchable nonlinear rheological property was designed by Yang and co-workers based on the urea/urease reaction (Figure 6D). [91] This system was grounded on the polyelectrolytes consisting of N,Ndimethylacrylamide (DMA), N,N-dimethylaminoethyl methacrylate (DMAEMA), nacryloxysuccinimide (ASM), and octadecyl bromide (C 18 Br), followed by immobilization of urease. The polymers were pH-sensitive and exhibited a shear thinning when pH was equal or greater than 7.5, otherwise exhibited a shear thickening at lower pH.…”

Urea‐Urease Reaction in Controlling Properties of Supramolecular Hydrogels: Pros and Cons

“…[32] Recently, the Yang group utilized the biocatalytic feedback of the urea-urease reaction to temporarily program the properties of non-Newtonian polymer gels. [33] Several pH-responsive polyelectrolytes were synthesized by the polymerization of N,N-dimethylacrylamide (DMA) and N,N-dimethylaminoethylmethacrylate (DMAEMA), followed by hydrophobic modification and urease immobilization. At a pH of 7.5 or higher, the deprotonated associative polyelectrolytes formed compact coil structures in solution, exhibited a shear thinning state.…”

“… Chemical fuel‐controlled field‐responsive fluidic materials developed by Yang group. [33] a) Photographs representing the time‐dependent non‐Newtonian behavior of fluid: i no shake‐gel before fuel addition, ii) transient shake‐gel behavior after fuel addition, iii) recovery of initial shake behavior after the energy dissipation with time. Adapted with permission from Ref.…”