Fig. 1: Microgeometry influences mechanically induced Ca²⁺ signaling.

a Schematic of a RBC passing through microenvironments with different geometrical features. When the cell passes through narrow spaces such as micro-vessel junction and endothelial clefts, pressure will induce membrane tension elevation. Mechanosensitive ion channels PIEZO1 (purple) on the cell membrane are then activated to allow Ca²⁺ influx. b Schematic illustration of the micropipette fabrication with different geometries which finely tuned the tip angle (θ) and diameter (d). c Representative snapshots of micropipettes with tip angle θ = 0°, 5°, and 10°. All three micropipettes had comparable tip diameter d = 1 μm. d Brightfield (top) and fluorescent (bottom) snapshots of the human red blood cell (RBC) being aspirated by the micropipette. When the tongue of the RBC is elongated during aspiration, a significant Ca²⁺ mobilization is observed by the increase in Ca²⁺ intensity in the fluorescent channel. e Representative traces of the RBC being aspirated by different micropipettes at ∆p = −20 mmHg. The fold change of Ca²⁺ intensity F/F₀ was utilized to examine the Ca²⁺ mobilization inside the aspirated RBC. To this end, the Ca²⁺ intensity increase was enhanced with both increasing tip diameter d and angle θ. a and b are created with BioRender.com released under a Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International license https://creativecommons.org/licenses/by-nc-nd/4.0/deed.en.