Carbon Nanotube Yarn Muscle: Prosthetic Finger Actuator

Actuator Drive

Drive voltage 0.0 V

Grip load 0.0 N

Cooling airflow 1.0×

Live Readout

Yarn temperature

22.0 °C

Contraction strain

0.0 %

Tendon output force

0.00 N

Finger closure

0 %

How it works

A twisted-and-coiled carbon-nanotube (CNT) yarn muscle is a nanomaterial actuator explored for lightweight, silent prosthetic-finger drives. Running current through the conductive nanotube yarn heats it resistively; the heat untwists the coil slightly, and because the coil is homochiral this converts to an axial contraction — no motors or gears needed.

Joule heating:     P = V² / R
Thermal balance:   C·dT/dt = P − h·(T − T_amb)
Actuation strain:  s(T) = s_max·(1 − e^(−(T−T_amb)/Tc))
Load line:         s_eff = s·max(0, 1 − F_load / F_stall)
Finger curl:       θ = θ_max·(s_eff / s_max)

Drive voltage — sets Joule heating power P = V²/R in the yarn.
Grip load — an opposing force (an object being grasped) that reduces the achievable contraction via the actuator's force–stroke trade-off, exactly like a real linear-actuator load line.
Cooling airflow — scales the convective heat-loss coefficient h, controlling how fast the yarn (and the finger) relaxes back open once voltage drops.
Pulse mode — square-waves the voltage on/off every second instead of holding it, showing the actuator's thermal response time.

Real-world relevance: Haines et al. (2014, Science) demonstrated twisted-and-coiled nylon and CNT-yarn muscles generating over 100× the specific work of natural muscle — a candidate nanomaterial actuator for tendon-driven prosthetic fingers that need to be light, silent and compliant.

CNT yarn muscle (coiled) Prosthetic finger phalanges

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