Human hand-inspired all-hydrogel gripper with a high load capacity formed by the split-brushing adhesion of diverse hydrogels

Abstract

Human hands are highly versatile. Even though they are primarily made of materials with high water content, they exhibit a high load capacity. However, existing hydrogel grippers do not possess...

Mechanical Robust GO/PVA Hydrogel for Strong and Recyclable Adhesion in Air, Underwater, and Underoil Environments

“…1,2 Several strategies have been proposed to prepare self-adhesive hydrogels, such as the introduction of catechol-containing polydopamine (PDA), 3−6 polyphenolic tannin (TA), 2,6,7 and biomimetic surface structure. 8−10 For many applications, such as underwater soft robots, 11 human implantable devices, 9,12,13 wound dressings, 10,14,15 tissue engineering, 5,8,16 and drug delivery systems, 15−18 hydrogels require dry and wet environments and wet adhesive properties. However, for viscous hydrogels, it has been shown that it is much more difficult to achieve wet adhesion than dry adhesion 3,19−21 because the water layer blocks the effective contact between the viscous hydrogel and the solid surface, leading to adhesion failure in water.…”

“…Adhesion is a common interaction between two different surfaces and plays an important role in many everyday and industrial applications. Self-adhesive hydrogels are potential candidates for epidermal bioelectronic conductors. , Several strategies have been proposed to prepare self-adhesive hydrogels, such as the introduction of catechol-containing polydopamine (PDA), − polyphenolic tannin (TA), ,, and biomimetic surface structure. − For many applications, such as underwater soft robots, human implantable devices, ,, wound dressings, ,, tissue engineering, ,, and drug delivery systems, − hydrogels require dry and wet environments and wet adhesive properties. However, for viscous hydrogels, it has been shown that it is much more difficult to achieve wet adhesion than dry adhesion ,− because the water layer blocks the effective contact between the viscous hydrogel and the solid surface, leading to adhesion failure in water. ,, In recent years, attempts have been made to repel the water layer by introducing hydrophobic solvents or monomers, to use highly hygroscopic components to absorb the water layer, ,, and to choose pure organic solvents as the distribution medium to exchange with the water layer to achieve underwater wet adhesion. , Although the obtained hydrogels show good wet adhesion in water, their reusability is always weak, and when the adhesion fails, they can no longer be used. ,, Another problem with the obtained hydrogels is that, unfortunately, most of the underwater adhesives lose their efficiency under oil. ,, Due to its much lower surface tension, the oil easily wets the surface, and the interfacial oil layer is more difficult to completely remove from the surface, which greatly weakens the adhesive strength between the hydrogel and the matrix under the oil, limiting their practical application.…”