Functional Stimuli-Responsive Gels: Hydrogels and Microgels

Abstract

One strategy that has gained much attention in the last decades is the understanding and further mimicking of structures and behaviours found in nature, as inspiration to develop materials with additional functionalities. This review presents recent advances in stimuli-responsive gels with emphasis on functional hydrogels and microgels. The first part of the review highlights the high impact of stimuli-responsive hydrogels in materials science. From macro to micro scale, the review also collects the most recent studies on the preparation of hybrid polymeric microgels composed of a nanoparticle (able to respond to external stimuli), encapsulated or grown into a stimuli-responsive matrix (microgel). This combination gave rise to interesting multi-responsive functional microgels and paved a new path for the preparation of multi-stimuli “smart” systems. Finally, special attention is focused on a new generation of functional stimuli-responsive polymer hydrogels able to self-shape (shape-memory) and/or self-repair. This last functionality could be considered as the closing loop for smart polymeric gels.

Reversibly and Irreversibly Humidity‐Responsive Motion of Liquid Crystalline Network Gated by SO2 Gas

“…Comparing with other stimulation, gas has prominent advantages that it can be released and removed conveniently in a large volume, providing great opportunities to trigger some industrial process . However, there are barely reports focusing on gas‐responsive LCN materials .…”

Construction of higher-order cellular microstructures by a self-wrapping co-culture strategy using a redox-responsive hydrogel

“…We postulate that this design and construction of a co-culture system by the wrapping cell sheet process should provide an alternative cell culture system. We used a stimuli-responsive cell culture substrate based on polymeric materials to achieve this goal [38][39][40] .…”

Progress in hydrogels for sensing applications: a review

“…Generally, a volume-phase transition of the network, a change in shape and size, change in its optical, mechanical, electric properties are the major typologies of responses. Hydrogels can be responsive to a wide variety of environmental stimuli [20]: temperature variation, pH solution change, light stimuli, the presence of certain biomolecules or free antigens are examples of external stimuli that can be sensed by hydrogels. More specifically, temperature is one of the most employed stimuli [21]: the temperature point at which a response is observed is called the critical temperature (T c ) and in that condition is possible to observe a phase change between the polymer and solvent within the system.…”