Antibody drop based handling with near-superhydrophobic mesh substrates overcomes condensation sticking

Superhydrophobic substrates facilitate low adhesion for biological liquid handling but are hampered by wetting state changes due to condensation. Here, meshed near-superhydrophobic substrates, that are easier to produce than two-tiered architecture substrates, are shown to provide good immunity to wetting state changes while imbuing high positional resistance to roll-off by tilting when tested with 5 and 10 μL volume drops (18° and 13° respectively) of human IgG antibodies in aqueous solution at both room temperature and 4 °C. Pneumatic actuation was applied to elicit horizontal drop movement over the near-SH surface without any fragmentation, wherein higher velocities can be achieved when smaller drops and higher air pressures are used (0.385 m/s at 33 mbar with the 5 μL drop). A non-contact mode of translating a protein drop towards a highly viscous oil-based adjuvant dispensed from a steel tip allowed for both drops to be combined and aspirated back up into the tip such that subsequent repeated cycles of pendant drop formation and upward aspiration allows for effective mixing to achieve a stable emulsion. The findings here advance the development of devices that enable improved antigen-adjuvant preparation by reducing the amount of reagents required and product losses from surface adsorption.