Skin‐Inspired Double‐Hydrophobic‐Coating Encapsulated Hydrogels with Enhanced Water Retention Capacity

Abstract

Traditional hydrogels always lose their flexibility and functions in dry environments because the internal water inevitably undergoes evaporation. In this study, a skin-inspired, facile, and versatile strategy for developing encapsulated hydrogels with excellent water retention capacity through a double-hydrophobic coating is proposed. The robust double-layer coating, which integrates a hydrophobic polymer coating with a hydrophobic oil layer simultaneously, can provide a barrier to prevent the evaporation of water. To overcome the weak interfacial strength between the hydrophilic hydrogel surface and the double-hydrophobic coating, (3-aminopropyl) triethoxysilane (APTES) is utilized as a chemical binding agent. Furthermore, the overall mechanical properties of the bulk hydrogel are not significantly affected, because the coating is only anchored to the surface and its thickness is much lower than that of the native hydrogel. Moreover, it is demonstrated that this proposed strategy particularly holds the capability of encapsulating various types and different shapes of hydrogels, leading to enhanced stability and a prolonged lifetime in air. Therefore, the proposed technology provides new insights for multifarious surface functionalization of hydrogel and broadens the range of hydrogel applications.

A Structural Gel Composite Enabled Robust Underwater Mechanosensing Strategy with High Sensitivity

“…Inspired by the mammalian skin constituted by the hydrophilic dermis and hydrophobic epidermis, [ 26,27 ] researcher generated the concept to generate a hydrophobic isolation layer on the hydrogel to achieve anti‐dehydration and anti‐swelling capabilities, by blocking the mass transfer pathway between the hydrogel and surrounding. [ 28–30 ] Nevertheless, considerable technical gaps need to be bridged to construct the hydrophobic layer on the surface without altering the bulk hydrogel structure. [ 31 ] Due to the incompatible mechanical properties and weak bond on the hydrophobic coating/hydrogel interface, [ 28 ] the obtained gel composite usually presents limited stretchability and low mechanical strength, as well as other drawbacks such as low/unstable conductivity and insufficient adhesion at underwater condition.…”

Reversing Hydrogel Adhesion Property via Firmly Anchoring Thin Adhesive Coatings

“…For traditional hydrogels, their flexibility and functions in dry environment are easily lost because of inevitable evaporation of network water molecules. [ 16 ] The low water loss rate in the harsh high‐temperature environment can more effectively prove their outstanding water retention capacity than a conventional, mild, room temperature environment. The water retention capacity of the PVA adhesive hydrogels was evaluated by placing them at 50 °C (humidity: 9%) for 24 h. For nontreated bare PVA hydrogel, it lost almost all water (≈99 wt%) and the residue became very stiff ( Figure a).…”

A Polyaniline Nanoparticles Crosslinked Hydrogel with Excellent Photothermal Antibacterial and Mechanical Properties for Wound Dressing

“…Evaluation of the Water Retention Capacity of the NPs@PAM Hydrogel: Water retention capacities of the hydrogel in air and in a simulated wound environment were evaluated as previously described. [30,31] Briefly, cylindrical hydrogel samples with a diameter of 10 mm and a thickness of 4 mm were placed in an air environment (25 °C, 30% relative humidity) and in simulated wound environments (37 °C and covered with tapes), respectively. At different intervals, optical sizes and weights of the hydrogel samples in the air and simulated wound environments were respectively recorded within one week.…”