US 6,583,533 · Granted 2003-06-24

The Pre-Stretched Polymer That Turns Electricity Into Motion

Imagine a rubber sheet that moves when you send electricity through it — but only if you stretch it first. This patent covers that trick: pre-stretching a special polymer makes it respond way better to electrical signals, turning them into actual mechanical movement you can harness to do work.

Curated and verified by the IsItPatented Editorial team

The plain-English version

What it protects

The claim covers electroactive polymers that are deliberately pre-strained (stretched) before electrical contacts are applied to them, along with the methods for making such devices. What's protected here is the combination of pre-strain plus electrodes plus the resulting mechanical deflection behavior — specifically, the improvement in converting electrical energy into mechanical motion that comes from that initial stretching step. The patent also covers compliant electrodes that conform to the polymer's shape and actuator designs that convert that deflection into useful work.

Why it matters

This patent addresses a fundamental engineering problem: converting electrical signals into mechanical movement efficiently. Pre-straining the polymer dramatically improves that conversion, which opens doors for actuators, robotic systems, and responsive devices. Sri International's work established a foundation for electroactive polymer technology that has influenced soft robotics and smart materials research. The patent's focus on practical fabrication methods also made the technology more accessible to engineers trying to build real devices rather than just lab demonstrations.

Real-world use

You'd encounter this in soft robotic grippers, artificial muscles in prosthetics, or any device that needs to flex or move without motors or gears — all triggered by applying voltage.

Original USPTO abstract

The present invention relates to electroactive polymers that are pre-strained to improve conversion from electrical to mechanical energy. When a voltage is applied to electrodes contacting a pre-strained polymer, the polymer deflects. This deflection may be used to do mechanical work. The pre-strain improves the mechanical response of an electroactive polymer. The present invention also relates to actuators including an electroactive polymer and mechanical coupling to convert deflection of the polymer into mechanical work. The present invention further relates to compliant electrodes that conform to the shape of a polymer. The present invention provides methods for fabricating electromechanical devices including one or more electroactive polymers.

Patent details

Publication number: US 6,583,533
Filing date: 2001-11-15
Grant date: 2003-06-24
Assignee: Sri International
Inventor(s): PELRINE RONALD E., KORNBLUH ROY D., PEI QIBING, JOSEPH JOSE P.
CPC class: F04B35/00

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