Figure 3.

Closed-channel devices – A) Demountable stack-assembled flow cell (adapted from Nasse et al. [74]) to measure biological specimens with high spatial resolution. Cells are visualized through diamond films grown on silicon wafer and seals are maintained by mechanical pressure from assembled manifold. The flow cell can be disassembled after measurement to reuse parts or access cells. B) Demountable stack-assembled flow cell (adapted from Tobin et al. [73]) with machined features on separate layers. Based on a modified Bioptechs FCS3 cell, the channel and chamber layers are pressed between two CaF₂ crystals for transmission measurement on a Bruker Hyperion microscope. C) Microfabrication allows more complex structures to be integrated into the flow cell and very precise control of water film thickness to be maintained uniformly over the entire measurement area. Device shown from Grenci et al. [87] has channels defined in a photosensitive polymer that covers the CaF₂ window. The device is permanently sealed by thermomechanical bonding.