Autonomously Oscillating Hydrogel Microspheres with High-Frequency Swelling/Deswelling and Dispersing/Flocculating Oscillations

Abstract

Fast swelling/deswelling and dispersing/flocculating oscillations of autonomously oscillating hydrogel microspheres (microgels) at periods of single-order seconds were accomplished. The design of the oscillating microgels is based on the incorporation of neutral and hydrophilic acrylamide monomers into conventional microgels to suppress the irreversible aggregation of the microgels during oscillation at high substrate concentrations and high temperatures in the Belousov–Zhabotinsky (BZ) reaction. In contrast to conventional microgels, the aforementioned microgels can carry out the BZ reaction under optimized conditions without irreversible aggregation at higher temperature, resulting in short oscillation periods (∼7 s) that were obtained from optical transmittance measurements. Furthermore, a macrogel composed of organized microgels was prepared, which also showed a remarkably fast swelling/deswelling oscillation (oscillation period: ∼23 s). This new type of oscillating microgel could be applied to advanced materials, e.g. to autonomously oscillating micropumps that imitate the human heartbeat.

Nanostructures, Thermoresponsiveness, and Assembly Mechanism of Hydrogel Microspheres during Aqueous Free-Radical Precipitation Polymerization

“…Functional molecules including drugs and proteins can diffuse into the microgel interior for later release in response to the environment. Thus, microgels are attractive for use in the human body. , Because of their fascinating properties, which combine the features of hydrogels and colloids, microgels are expected to find use in numerous applications, including molecular separation, , catalysts, , biosensors, , emulsifiers, , actuators, − and model systems for cells, glasses, , and crystals. , …”

Stimuli responsive dynamic transformations in supramolecular gels

“…Based on same strategy, the Suzuki group further developed an oscillating microgel system which exhibited fast swelling/deswelling and dispersing/flocculating oscillation. 437 They suggested that this system could be explored in fabricating autonomously oscillating micropumps similar to human heartbeat. Ballav and co-workers undertook a similar strategy to convert a coordination polymer gel into a conducting polymer gel.…”

Nanostructure and thermoresponsiveness of poly(N-isopropyl methacrylamide)-based hydrogel microspheres prepared via aqueous free radical precipitation polymerization

“…Due to their desirable properties, microgels have found applications, not only in a dispersed state, for example as carriers for drug-delivery systems, [5][6][7] in molecular separations, [8][9][10][11] and in functional catalysts, [12][13][14] but also in assembled states, for example as cell scaffolds, 15,16 sensors, 17,18 emulsi-ers, 19,20 and actuators. [21][22][23] The rst reported microgels were thermoresponsive poly(Nisopropyl acrylamide) (pNIPAm)-based microgels cross-linked with N,N 0 -methylenebis(acrylamide) (BIS). 24 These microgels have a volume-phase-transition temperature (VPTT) of $32 C and their physicochemical properties change quickly when the temperature increases beyond this point.…”