PDES • 3D experiment

Overall apparatusInitializing 3D scene…

Drag to rotate · scroll or pinch to zoom · use Sample close-up to inspect the fiber

Component legend

1. OscilloscopeRecords gate and drain voltage signals.

2. DC power supplySupplies electrical energy for heating.

3. USB waveform generatorProvides the MOSFET gate-control signal.

4. Breadboard and MOSFETConnects the circuit and switches heating current.

5. PDES specimenContracts in response to Joule heating.

6. Upper clamp and gripMaintains the fixed specimen attachment.

7. Lower grip and loading hardwareApplies the suspended mechanical load.

8. Ruler and indicator LEDProvide spatial calibration and command timing.

Active length L(t)30.00 mm

Shortening ΔL0.00 mm

Modeled temperature23.0 °C

Contraction strain indicator

Contraction strain0.0%

0–25% display range · ε = [L₀ − L(t)] / L₀ × 100% · L₀ = 30 mm

Oscilloscope · gate and drain voltages

CH1 · VGSCH2 · VDS (dashed)

Both probe ground clips connect to common return. Drain voltage is not current.

Contraction strain versus time

Positive contraction; this curve comes from the model, not measured video.

Active specimen length versus time

Specimen temperature versus time

Circuit connections and test points

Heating path: supply + → coated specimen → thin wire → drain → source → supply −.

Connection	Destination
Generator output	MOSFET gate · G
Generator return	Common return · S
CH1 tip · blue	Gate · G
CH2 tip · purple	Drain · D
Both scope ground clips	Common return · S
LED + 6 kΩ series branch	Gate to common return

Red: supply positive. Black: return. Yellow: generator command. Green: specimen return to drain. Thin blue and purple leads represent the probe tips; the black scope return represents both common-ground connections. The support frame is not an electrical conductor in this model.

How length and strain are measured

Track the upper and lower grip boundaries, calibrating video pixels against the ruler. Their separation gives L(t). Use the initial loaded separation as L₀. Shortening from 30 to 27 mm gives 10% contraction. The orange markers and vertical bracket show the tracked boundaries. Cycle peak-to-peak strain is the difference between a cycle’s maximum and minimum strain, in percentage points.

Model assumptions and limits

Photo-informed geometry, not measured CAD dimensions. Loaded active length 30 mm; total suspended load 10 g. Coating and wire are each 1 Ω. On-state current = min(V/2 Ω, 1 A). Coating power = I² × 1 Ω. Ambient 23 °C; thermal resistance 70 K/W; thermal time constant 3 s. Equilibrium contraction = 0.25% per kelvin, limited to 25%; mechanical response time 0.25 s. The load remains fixed. No resonance, creep, contact degradation, changing resistance, or predictive material constitutive model. LED follows the command. Efficiency is not calculated. Replace assumptions with measurements before using the model quantitatively.