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This paper reports studies to investigate the relationships between hydrophobicity of biochar surface and soil water retention. The studied biochars were produced from acacia wood, cashew wood and bamboo. The resulting materials were oxidized via liquid oxidation to generate hydrophilic biochars containing oxygenated functional groups on the surface. All biochars were characterized and their ability as soil additives to enhance water retention was assessed. Our results suggest that hydrophobicity/hydrophilicity of biochars is not the major factor governing water retention ability of this particular soil. However, hydrophilicity of biochar helps improve soil permeability by providing better wettability to the soil.

Lubricant-infused textured surfaces have gained much attention as liquid-repellent surfaces owing to high surface stability compared to their superhydrophobic counterparts. In this study, polydimethylsiloxane (PDMS) micro-structures (width: 20 μm, height: 80 μm), were fabricated using soft lithography. Effects of micro-structural geometry, including pillar-type (pillar, discrete ridge) and hole-type (hole, continuous ridge, circular rings with eight stripe supporters), on infiltration capability of the lubricants with different viscosity (Krytox-103; η: 0.131 Pa.s, Krytox-105; η: 0.737 Pa.s, paraffin oil; η: 0.112 Pa.s) were investigated. Partial infiltration was observed on the pillar-type micro-structures, while more completed infiltration was obtained on the hole-type micro-structures. More viscous Krytox-105 resulted in completed infiltration for all micro-structures, thus creating a slippery liquid-infused porous surface (SLIPS). The best SLIPS, signified by a low sliding angle and a fast speed of water droplet, prepared from the hole pattern infused with Krytox-105 exhibited good anti-fouling performance against chlorophyll and milk yogurt.