Pinky-Powered Photons (DRAFT) Description Pinky-powered photons is a low-cost project where participants make and take home a colorful LED light powered entirely by their fingers. Younger visitors merely "package" the electrical element into their own animal creation or shake light while older visitors actually solder the electrical parts together and then create their own design. Visitors learn that piezoelectric materials are substances that respond to electricity or a force being applied. Here, pressing a finger on the piezoelectric material produces an electrical charge that causes the LEDs to flash. Visitors learn that piezoelectric materials transform mechanical energy into electrical energy that can cause LEDs to illuminate. Visitors also experience a direct relationship between mechanical force and light energy. Participants are encouraged to save their creations as the parts can be re-used for other more advanced projects. Audience Ages four and up work if using school glue and packing tape. Allow 10 to 14 minutes. Ages eight and up work with soldering iron, adhesive and packing tape. Allow 20 to 24 minutes time Fig. 1 Image of animal creations Science topics Piezoelectric materials, energy, electricity and LED’s (Light Emitting Diodes). Approximate material cost per is about 45 cents per person, assuming existing soldering iron and solder. Objectives Major concepts  That there are many different types of substances and some have amazing properties that can be useful.  Energy, whether from fingers or other sources, can be transformed into other forms of energy.  That piezoelectric materials can transform a force into electricity and, conversely, electrical energy into force or movement.

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Minor concepts  Movement contains kinetic energy and that energy can be changed into other forms of energy.  Soldering is a good skill for future experimenters and makers. Materials  Ordinary piezoelectric guitar pick-up*, 20 and 34 mm diameter disks with leads already attached. Ordered online.  One watt LED’s without heat sink, various colors. Two LEDs are required for each piezo disk. Basically any LED will work.  Foam or cardboard pieces  Tape, super glue  Soldering iron, solder and iron holder required for older participants  Plastic bottle, small food condiment container from recycling  Heavy duty scissors or wire cutters  Latex balloons or other membrane if making musical instrument  wire strippers The Activity Blinky Creatures Younger visitors use the pre-soldered piezo generator and LEDs components, as in Fig. 2, to make push-powered creations. Slowly pushing and releasing on the piezo disk causes one and then the other LED to flash. Rapid tapping causes both LEDs to be lit at the same time. For the googly-eyed creature shown in Fig 1, foam rings are die cut from 1/8 inch thick sheet foam purchased from Michael’s. The ring is glued to the backing sheet and piezo element is placed with the wires down so that the do not show. The LED “eyes’ are arranges as desired and the entire piece covered with packing tape. Be sure to completely cover and secure all the electrical parts.

Fig. 2 Piezoelectric electrical system shown with piezo pick-up and LEDs. The light colored center is the piezoelectric material *

Currently guitar and musical pick-ups contain an inert ceramic film that bears Lead. While the lead is chemically bound, we recommend covering piezo disk with packing tape or other material. Broken piezo disks should be discarded. Intact disks can be reused for more advanced projects.

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Fig. 3 Electrical diagram and actual components used by older participants.

Older participants are instructed on soldering to make electrical connections, and warned hot metal and burns, etc, followed by a demonstration. They select two LEDs of whatever color and are shown how to strip off ½ inch of insulation from the two wires on the piezo disk. Solder on one LED to the two wires and test operation by gently tapping on the disk. You should see a brief flash and note that flashing seems to stop working with lots of rapid taps. This is because a charge build-up happens if we use just one LED. To figure out the proper orientation of second LED hold the second LED onto the exposed wires and test by tapping again. Most, but not all LEDs have their polarity clearly marked. Properly connected, the LEDs will appear to alternatively flash. With both LEDs soldered onto the wires coming from the piezo you have a ready to use electrical system. Shake Lights Enclose the piezo element is a recycled fast food condiment container to make a shake light. To use the piezo element as a striker to fire the LEDs the wire connection on the piezo disk must be reinforced. Just apply a small blob of hot glue to the piezo disk and wire junction. Allow enough wire for the piezo disk to flop and force the lid on.

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Fig. 4 Shake flash light made using condiment cup

Fig. 5 Plastic bottles cut to make open recycled ended drum. Shown with balloons.

Shake Sounders Want sound? Light-up drums and other sounders can be made from soda and other plastic bottles. Begin by cutting one or both ends off a strong plastic bottle for the drum body. The wires on the piezo disk are reinforced with hot glue at their weak point. Then the entire electrical system is hot glued to the inside of the drum. Next a balloon or other suitable membrane is cut and stretched across opening to form the drum head. The piezo disk must be lose enough to flop and hit the membrane. Use tape or a rubber band to secure the membrane to the bottle. Castanets and other instruments are possible. More advanced students may use the piezo disk as sensor. The Science Piezoelectric materials are unique solid and plastic materials that produce electricity when squeezed and, “squeeze” or move themselves when electricity is applied. These materials are widely used today in musical instruments, push buttons, spark igniters and other sensors where they convert vibration and sound into electrical power. LEDs (Light Emitting Diode)s are electrical devices that are very efficient at converting electricity into light. Putting the two together, we have an inexpensive piezoelectric generator powering LED light. There are a number of materials that are piezoelectric. When you press on them they produce a positive voltage pulse that quickly turns to a negative voltage as the pressure is released. Think of a jagged stock market graph with positives 4

and negatives. The voltage produced closely follows the amount of force you apply, making these materials a “sensor” of force. Some piezo materials produce thousands of volts when struck, and an ordinary barbeque lighter may produce 30,000 volts. Here, ordinary guitar “pick-ups” and disk-type (piezoelectric) buzzers, essentially metal disks with a thin sheet of piezoelectric material glued to them., produce about 200 volts! The short but safe pulse is enough to light one watt LEDs. It is important to package or seal the piezo side of the disk to prevent the ceramic material, if broken, from escaping. While inert, it is a Leadcontaining ceramic. The good news is that pick-ups are re-useable and are participants encouraged to remake their project when they grow bored. LEDs only draw power and light up when they are correctly connected to the generator. If the polarity is not proper then they do not draw power. For older participants soldering an electrical system they first connect a LED of their preferred color to the piezo element and then test light production by tapping on the piezo element. The LED has a polarity, meaning that it will only illuminate when the correct polarity of voltage is applied. Since tapping produces a positive voltage on the “downside” and a negative voltage as the disk rebounds upward, the LED will only light on the downside or the rebound. Repeat tapping causes a charge builds-up on the unused side of the piezo and the LED to actually stop lighting. Adding a second LED that is inverted allows for both “phases” of the piezo generator to be used for power and nearly continuous light to be repeated tapping. More advanced student are encouraged to research other uses for the elements as a sensor, microphone, vibration sensor and many other projects. Acknowledgments This project was supported by SPIE – The International Society for Optics and Photonics, OSA – The Optical Society, Thorlabs – UFO, IPG-Photonics, and MiLight. Authors Elizabeth Dreyer and Timothy R. Jones†

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Corresponding author [email protected] 5