Fig. 1.

Direct foam writing. (A) Schematic view of direct foam writing of porous filamentary features. (B) Cross-sectional view of the PSF ink microstructure, in which entrained bubbles are surrounded by colloidal particles. (C) Bubble stabilization is enabled by controlling the contact angle of the colloidal particles such that they spontaneously adsorb onto the gas–liquid interface. Image of the wet foam microstructure (D) immediately after formulation and (E) after 1 wk of aging. (Scale bars: 500 μm.) (F) SEM micrographs of the sintered foam show a closed, highly macroporous morphology with cell wall thicknesses as thin as one grain (G). (Scale bars: F, 100 μm; G, 5 μm.)