SupercapacitorA capacitor is a device used for storing electric charge [1]. A simple parallel plate capacitor (shown in Figure 7) consists of two parallel conductive plates separated by an insulating layer called a dielectric. The insulating layer prevents electric charges from flowing between the two plates.
If the ends of a capacitor are connected to a power source (such as a dynamo), the voltage from that power source will drive the electrons from one of the capacitor's conductive plates to the other, charging the capacitor. Disconnecting the power source at this point will trap (or store) the charges on the capacitor's plates. One plate will be negatively charged with electrons and the other plate will be positively charged with an equal number of ions. The amount of charge that can be stored on these plates depends on a property of the capacitor known as capacitance. A capacitance of a capacitor depends on the surface areas of its plates, the type of insulating material between its plates, and the distance between its plates [2]. In general, the larger the capacitor, the more charge it can store. Once a capacitor is charged, it too can be used as a power source. Any capacitor that is small enough to fit inside Bigshot would be too small to hold enough charge to take even a single photo. Fortunately, however, recent breakthroughs in materials science have given rise to a new type of capacitor called a supercapacitor [3], or "supercap" for short. Rather than having two plates separated by a thick insulation layer, supercaps use two thick layers of conducting material separated by a very thin (often a few nanometers wide) insulating layer, as shown in Figure 8. The two conducting layers are made of a porous material (similar to charcoal or sponge) to dramatically increase their surface area. Since the charges can be held inside the plates' pores in addition to outside on their surfaces, supercaps can store significantly greater amounts of charge than regular capacitors can. Bigshot's supercap can store enough charge to capture 6 to 10 photos before it needs to be recharged using the dynamo.
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