fig2

Figure 2. Schematic of (A) SFA and (B) ITLFFA techniques. Adapted from ref.^[35] for (A), Copyright, 2021 Elsevier; and ref.^[45] for (B), Copyright 2016, The Royal Society of Chemistry. CCD: Charge-coupled device; FECO: fringes of equal chromatic order; SFA: surface forces apparatus.