Piezoelectric Nanowire Nanogenerator

Press Cycle

Compressive strain amplitude 0.20%

Press frequency 1.5 Hz

External load R_L 200 kΩ

Nanowire array density 10 × 10

Live Output

Instant. strain

0.00%

Stress σ

0 MPa

Open-circuit V_oc

0 mV

Load voltage V_L

0 mV

Output power P_L

0 nW

Peak power (session)

0 nW

How it works

This models a vertically integrated nanogenerator (VING): an array of upright, single-crystal ZnO nanowires (wurtzite structure — non-centrosymmetric, so it is intrinsically piezoelectric) sandwiched between a bottom electrode and a top electrode that presses down and releases. Each compression/release half-cycle strains every nanowire along its polar c-axis and generates a transient voltage.

Stress:            σ = E · ε            (E ≈ 140 GPa for ZnO along c-axis)
Piezoelectric:     D = d33 · σ           (d33 ≈ 12.4 pC/N for ZnO)
Voltage constant:  g33 = d33 / ε33       (ε33 ≈ 8.5 · ε0)
Open-circuit V:    Voc = g33 · σ · L     (L = nanowire length)
Loaded output:     VL = Voc · RL /(RL + Rs/N)
Power delivered:   PL = VL² / RL

Compressive strain amplitude — how far the top electrode compresses the array each cycle; sets the peak stress σ and hence Voc.
Press frequency — how fast the compress/release cycle repeats (the mechanical input, e.g. finger tapping or footstep-driven harvesting).
Load resistance RL — the external circuit the device drives. Power is only maximised when RL is matched to the array's internal source resistance Rs/N (impedance matching), exactly as for any real electrical source.
Array density — more nanowires in parallel lower the combined internal resistance Rs/N, raising the deliverable current and power without changing the single-wire Voc.

Each nanowire is colour-coded by its instantaneous piezopotential: green for the compressed, positively-charged state and violet as it relaxes back through zero. In a real device a Schottky (rectifying) contact at the electrode interface keeps this alternating charge flow from short-circuiting internally, which is why the array can drive an external load instead of just cancelling itself out. Real devices output far less than this idealised d33-relation predicts, because mobile free carriers inside the semiconducting ZnO screen part of the piezopotential — a well-studied effect that gave rise to the field of "piezotronics".

Compressed (+piezopotential) Relaxed / releasing

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