Paper Generators: Harvesting Energy from Touching, Rubbing and Sliding

Project Members

Ivan Poupyrev (Disney Research Pittsburgh)
M. Emre Karagozler (Disney Research Pittsburgh)
Eric Brockmeyer (Disney Research Pittsburgh)

 

We present a new energy harvesting technology that generates electrical energy from a user’s interactions with paper-like materials. The energy harvesters are flexible, light, and inexpensive, and they utilize a user’s gestures such as tapping, touching, rubbing and sliding to generate energy. The harvested energy is then used to actuate LEDs, e-paper displays and other devices to create interactive applications for books and other printed media.

 

[Press Release]

Technical Details

RE_diagram

Paper Generators are based on electrets: materials that hold quasi-permanent electric charge. Our implementation makes use of PTFE (Polytetrafluoroethylene) sheets, commonly known by the brand name Teflon®. When the PTFE sheet is rubbed with ordinary paper, opposite-polarity charges accumulate on the surfaces of the paper and the PTFE due to the triboelectric effect, forming the electret (Figure a). Because PTFE has a lower electron affinity than paper, charge on the PTFE is negative. When the PTFE sheet is stacked with conductive layers that serve as electrodes, such as silver coated polyester sheets or paper with printed conductive ink, the charge on the PTFE attracts free charges of opposite polarity, which then accumulate on the surface of the conductors, as shown in Figure b. This structure forms the basis of Paper Generators.

The operation of the Paper Generators relies on the movement of the two conductive sheets relative to each other and the electret, PTFE. Energy is created when a user moves electrodes. As the relative positions of the sheets change, the distribution of the induced charges, the electric field, and the total capacitance between the conductors change, resulting in an electric potential difference between the conductors (Figure c). Hence, the movements of the sheets and the field source are converted into electrical potential energy that can do work.

The same principle of operation applies to the horizontal movement of the top electrode (sliding). It is also possible to replace the top electrode with the user’s hand. In this scenario, the user holds and rubs the PTFE sheet on and off the bottom electrode, while touching the other end of the voltmeter with his free hand. The circuit is completed through the users body. These different Paper Generator configurations and structures allow for energy generation using different user gestures, such as tapping, rubbing, touching, rotating and sliding.

Paper Generators - Rocket and stars with LEDs

When a user taps a button made out of paper, harvested energy lights up LEDs placed at the rocket’s engine and the stars. Because the generator voltage is very high, many LEDs can be lit simultaneously.

Paper Generator Button

The moving part of the paper button is opened to reveal the PTFE sheet. The underside of the button is made out of silver coated polyester, and it is separated from the bottom sheets by black foam rubber.

E-paper actuated using Paper Generators

E-paper displays are an especially suitable application for Paper Generators since they require high voltages but very little power. Here, When the user creates energy by using a rubbing Paper Generator, a pattern on the e-paper display shows a cat’s face.

E-paper front and back

An image of a light bulb is patterned on the e-paper display.

Paper Generator Game

The harvested energy can be stored temporarily to enable more interactive applications. In this game, two users compete to harvest energy faster by tapping paper buttons; the first player to light up his respective LED wins the game.

Tapping and Rubbing Paper Generators

Different types of Paper Generator structures are designed to match different user gestures. Here, the printed Paper Generator structures that utilize the tapping and the rubbing gestures are shown.

 

Rotating Paper Generators

Energy can also be harvested using rotating Paper Generators. When the user turns the rotating top electrode, harvested energy lights up and LED. Similar structures, where the top electrode slides instead of rotating, can be easily implemented.

Button connected to an Oscilloscope

When a user presses the button, a voltage difference is created between the top and bottom sheets of the Paper Generator. This voltage difference can be easily measured using an an oscilloscope. Contact and release generate opposite polarity voltage spikes.

Patterns on e-paper can be displayed sequentially.

Patterns on e-paper displays can also be displayed sequentially. When the user rubs the Paper Generator, a passive circuit allows for the characters H-E-L-L-O to be displayed sequentially, creating an animation.

Paper Generators can power multiple LEDs

Because the generated voltage is very high, many LEDs can be lit simultaneously.

Rotating Paper Generators

Paper generators can be used to communicate with external devices such as laptops, tablets and phones. A signal is sent to the computer using an infrared (IR) emitter circuit, which triggers an animation on the computer.

Tapping and Rubbing Paper Generators

Here, the printed Paper Generator structures that utilize the rotating and the sliding gestures are shown.

Publications

Paper Generators: Harvesting Energy from Touching, Rubbing and Sliding
January 1, 2013
In Proc. of UIST’13, ACM
Paper File [pdf, 6.43 MB]

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