Schematic of x-ray ablation for HA hydrogels. The depth and the width in a single channel are tunable by adjusting the x-ray dose and the mask width. As an example, a HA architecture of -width coherent microchannels fabricated using the x-ray ablation is demonstrated.
(a) Sequential in situ microradiographs showing a gel-to-sol transition of approximately 1 mg of HA hydrogel cross-linked with DVS during x-ray irradiation of approximately . Spherical silica balls initially remained in the top region of the ”gel” HA medium, and then fell down to the bottom of the capillary tube during irradiation, clearly indicating a gel-to-sol transition. (b) Sol-gel phase diagram for the x-ray dose rate and the irradiation time. The ablation kinetics is determined by the total x-ray dose.
UV spectra and FT-IR spectra (inset) of HA-DVS hydrogel sample after irradiation with x-rays of approximately . The arrow and the gray zone indicate the absorption band evolution at 260–270 nm in the UV spectra and at in the FT-IR spectra. The rapid band evolution within 1 min indicates a rapid x-ray-induced chain scission in HA.
UV spectra and FT-IR spectra (inset) of HA raw materials (powders or solutions, ) after irradiation with x rays of approximately . The same band evolutions of HA raw materials and HA-DVS hydrogel suggest that the x-ray irradiation cleaves the HA backbone.
GPC analysis of HA and HA-DVS hydrogel samples after x-ray irradiation up to 60 s. The GPC data show that the MWs of the HA hydrogels and the HA-DVS hydrogels significantly decreased with the x-ray irradiation (dose ), indicating the chain scission by the x-ray irradiation.
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