Writing with Fluid: Structuring Hydrogels with Micrometer Precision by AFM in Combination with Nanofluidics

Abstract

Hydrogels have many applications in biomedical surface modification and tissue engineering. However, the structuring of hydrogels after their formation represents still a major challenge, in particular due to their softness. Here, a novel approach is presented that is based on the combination of atomic force microscopy (AFM) and nanofluidics, also referred to as FluidFM technology. Its applicability is demonstrated for supramolecular hydrogel films that are prepared from low-molecular weight hydrogelators, such as derivates of 1,3,5-benzene tricarboxamides (BTAs). BTA films can be dissolved selectively by ejecting alkaline solution through the aperture of a hollow AFM-cantilever connected to a nanofluidic controller. The AFM-based force control is essential in preventing mechanical destruction of the hydrogels. The resulting "chemical writing" process is studied in detail and the influence of various parameters, such as applied pressure and time, is validated. It is demonstrated that the achievable structuring precision is primarily limited by diffusion and the aperture dimensions. Recently, various additive techniques have been presented to pattern hydrogels. The here-presented subtractive approach can not only be applied to structure hydrogels from the large class of reversibly formed gels with superior resolution but would also allow for the selective loading of the hydrogels with active substances or nanoparticles.

Development of a Mosquito Repellent Formulation Based on Nanostructured Lipid Carriers

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Mechanically Controlled and Consecutively Boosted Circularly Polarized Luminescence of Nanoassemblies from Achiral Molecules

“…In this work, we replaced the cinnamate with benzoic acid (BTABA), which has been widely reported in supramolecular gel systems. − As shown in Figure b, we found that the VAA method is still effective in the BTABA system, and the chiral bias is drastically boosted ( g lum = ±4.35 × 10 –2 ). More importantly, the resultant assemblies can be used as chiral seeds and further control the handedness of CPL in the following VAA treatment.…”

Steering Nanohelix and Upconverted Circularly Polarized Luminescence by Using Completely Achiral Components

“…Analogous to previous benzene-1,3,5-tricarboxamide (BTA) derivatives, − BTABA can form helical nanoribbons in a mixture of good solvent (DMF) and poor solvent (H 2 O) with the volume ratio of 6:4. However, the sample has no optical activity due to the equal number of left- and right-handed helixes.…”