Table 1.

Brief summary of hydrogels with various swelling features

Hydrogel types	Swelling ratios	Merits	Demerits	Fabrications	Biomedical applications	Refs.
High‐swelling hydrogels	>150%	High wound exudates absorption capacity, high cell recruitment and migration, high drug entrapment, diffusion and release	Macroscopic volume expansion, poor mechanical stability, weakened bioadhesion and conductivity, risk of tissue compression damage	Chemical modification, hydrophilic polymer self‐crosslinking, adding small molecule cross‐linkers	Tissue engineering, drug delivery	[12]
Non‐swelling hydrogels	0–150%	Excellent dimensional stability, long‐term wet‐adhesion performance, persistent mechanical strength and conductivity	Low drug loading and release efficiency, cannot exchange nutrients and bioactive molecules, low cell attachment, complex cross‐linked network design process	Functional polymer self‐crosslinking, synthesizing amphiphilic copolymer, polymer self‐assembling, adding small molecule cross‐linkers, solvent exchange, surface hydrophobic grafting	Tissue engineering, bioelectronics	[13]
Shrinkable hydrogels	<0%	Stimuli‐responsive, mechanically active, dynamic stiffening and contraction, promoted cell attachment and condensation, remotely controlled drug release	Risk of tissue tension damage, complicated molecular structure regulation process	Synthesizing stimuli‐responsive copolymer, introducing a second polymer, adding small molecule cross‐linkers	Tissue engineering, drug delivery	[14]