This is a genuine 2D model, not a flattened version of the 3D scene. The 3D simulator advances the capsule along its tube at a constant visual rate and only labels elapsed hours afterwards. Here the capsule's centimetre position x(t) is the thing being integrated directly, against each segment's own real average length and residence time, so the on-screen pill actually lingers in the stomach and crawls through the colon in the correct proportion — not just in the clock readout:
dx/dH = L_i / T_i (segment i: length L_i cm, residence time T_i h)
Esophagus L=25cm T≈0.003h → ≈8900 cm/h (fast)
Stomach L=15cm T≈2h → 7.5 cm/h (slow, acid mixing)
Duodenum L=25cm T≈0.1h → 250 cm/h
Jejunum/Ileum L=600cm T≈3.5h → 171 cm/h
Colon L=150cm T≈20h → 7.5 cm/h (slow, mass movements)
Enteric-coated release (same first-order dissolution physics as real ingestible capsules) triggers once local pH ≥ your threshold, then decays exponentially:
release triggers when pH(x) ≥ pH_c
M(t) = M0 · e^(−k(t − t_release)), k = 0.35 h⁻¹
RF telemetry is computed from the capsule's live 2D position, not a lookup: the schematic torso is a circle of radius 15 cm, the capsule's depth is its distance to that boundary along the ray from the torso centre, and the received signal follows a log-distance path-loss model plus tissue absorption that grows with both depth and carrier frequency:
depth = R_torso − |capsule position|
RSSI(dBm) = P_tx − 20·log10(d/d0) − α(f)·depth
α(f) = α0 · (f / f0) [higher frequency ⇒ faster tissue absorption]
- Peristalsis rate — scales every segment's velocity together, so the whole trip speeds up or slows down without breaking the relative dwell-time ratios above.
- RF carrier frequency — near 2.4 GHz (BLE-class) attenuates in tissue much faster than near 400 MHz (the MICS medical-implant band); watch the RSSI bar sag as you raise it.
- pH threshold — a low threshold releases in the stomach itself (defeating an enteric coating's purpose); a realistic 5.5–6.5 releases once the duodenum's bicarbonate neutralizes gastric acid.
- The bottom strip is a live time-series of pH, normalized signal strength and released fraction — a second, independent way to read the same physics that the schematic view can't show at a glance.
Real-world relevance: this distance-integrated transport model is the same reasoning pharmacokineticists use to predict when and where an oral dosage form will actually release its payload, and the RF link budget mirrors the design constraint every capsule-endoscopy and ingestible-sensor product has to solve.