SORT THE CELLS
Fund the wave, sort by size
Two IDTs launch surface acoustic waves toward each other, forming a standing wave with a pressure node down the center. Dial in the drive voltage so the large cells get funneled to the node — without dragging the small ones in too.
Small cells
❌ at the edges
Large cells
❌ at the edges
CHALLENGE COMPLETE
🔊 Every batch sorted clean
+55 XP
Bigger particle → bigger acoustic force, same viscous drag
The standing-wave force scales with particle volume, but Stokes drag only scales with radius — so past a certain drive strength, larger cells cross the channel to the node well before smaller ones do. The real chip this is modeled on drives its IDTs at ~10V, launching a wave at a wavelength of about 240 µm — a resonance the design team confirmed by simulation at 16.473 MHz before ever cutting a wafer.