Paper : Electricity Generated by Human Body



As we learned in intro physics, everything is made up of atoms, and atoms are made up of protons, neutrons and electrons. Protons have a positive charge, neutrons have a neutral charge, and electrons have a negative charge. When these charges are out of balance, an atom becomes either positively or negatively charged. The switch between one type of charge and the other allows electrons to flow from one atom to another. This flow of electrons, or a negative charge, is what we call electricity. Since our bodies are huge masses of atoms, we can generate electricity. A resting male can put out between 100 and 120 watts of energy, in theory enough to power many of the electronics you use, such as your Nintendo Wii (14 watts), your cellphone (about 1 watt) and your laptop (45 watts). Eighty percent of body power is given off as excess heat.


When we talk about the nervous system sending "signals" to the brain, or synapses "firing," or the brain telling our hands to contract around a door handle, what we're talking about is electricity carrying messages between point A and point B. It's sort of like the digital cable signal carrying 1s and 0s that deliver "Law & Order." Except in our bodies, electrons aren't flowing along a wire; instead, an electrical charge is jumping from one cell to the next until it reaches its destination.

Electricity is a key to survival. Electrical signals are fast. They allow for a nearly instantaneous response to control messages. If our bodies relied entirely on, say, the movement of chemicals to tell our hearts to speed up when something is chasing us, we probably would've died out a long time ago.

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The body generates an electrical current by changing chemical concentrations in and around the nerves.

Basically, when a nerve signal is sent, potassium ions flood out of nerve cells and sodium ions flood in. Both of these ions have slightly different charges and so the difference in concentrations inside and outside the nerve cell of the ions means that a charge is created inside the nerve cell.Static is not generated by the body, but simply by things passing over the skin. This knocks electrons from whatever brushes against the skin, or even from the skin. These electrons build up until there is a great enough charge for them to discharge across to something else... which we see as a spark.

Magnets do not affect the electrical currents within the body.
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A device that produces electricity from blood could be used to turn people into "human batteries". Researchers in Japan are developing a method of drawing power from blood glucose, mimicking the way the body generates energy from food. Theoretically, it could allow a person to pump out 100 watts - enough to illuminate a light bulb. But that would entail converting all the food eaten by the individual into electricity. In practice, less power would be generated since food is needed by the body. However the scientists say the "bio-nano" generator could be used to run devices embedded in the body, or sugar-fed robots.

The team at electronics giant Panasonic's Nanotechnology Research Laboratory near Kyoto has so far only managed to produce very low power levels. But the scientists ultimately expect to gain much greater performance from the device. The battery is based on an enzyme capable of stripping glucose of its electrons, "It is like the metabolism of food. Human bodies can process glucose and obtain energy. When glucose is oxidised, electrons can be obtained.
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Principle

A thermoelectric generator

A thermoelectric generator ((TEG)) draws electrical energy from differences in temperature. The generators previously required a difference of several tens of degrees to be effective. The number of devices that could be assisted by this development is huge. Not only will consumer electronics such as iPods and mobile phones experience a surge in battery life, but situations in which a person is subjected to an array of more extraordinary gizmos could be greatly simplified, and possibly even revolutionized. A soldier who needs to carry several vitally important electrical items would be not be restricted by an invisible leash tying him to the nearest electrical recharging point. A hospital would be able to move patients with greater ease, and cut electrical cost, by running a patient’s numerous health monitors off their own body.

Wrist watches using kinetic energy as a power source have been on the market for a while – but scientists envision a grander future for the method, as the generators are scaled up in efficiency and size. Kinetic energy is created from movement, and with so many modern products creating near constant vibrations, it’s another example of how ambient energy could be quite easily garnered from a modern working environment. A kinetic generator affixed parasitically to vibrating machines in a factory could create the energy required to power the lights. As with TEGs, scaling the generators down in size once they have reached optimum efficiency may also have benefits. Devices could be powered by the process of breathing, or even by the flow of blood.

Just because ambient energy is about harnessing relatively small forces does not mean that it need be restricted to powering small things. Piezoelectricity is the charge generated by certain materials when placed under stress, for example the energy generated by footsteps. Previously tried and dismissed by the US army, which attempted to apply it on an individual level, the concept is seeing real success in larger scenarios. Japanese train stations are collecting the piezoelectric energy of commuters walking through the gates, and MIT is working on a “crowd farm” which would use a special floor to harness the energy created by the circulation of a large amount of people.

Ambient energy is driven predominantly by researchers seeking more eco-friendly solutions, and by corporations who wish to cut costs. But, true to its nature, it is more than likely it will have the lucky side-effect of powering many exciting and unforeseen technological innovations in the process.

A thermoelectric device placed on skin will generate power as long as the ambient air is at a lower temperature than the body. A patch of material one square centimeter in area can produce up to 30 microwatts. Place these generators side by side to multiply the amount of power being harvested.

A nanometre

A nanometre is one-billionth of a metre; -- a human hair is roughly 100,000 -- generator which produces electrical current with the bending and relaxing of nanometre wires. These movements mimic the movements of body muscles. These nanoscale components are called ‘nano-generators' or the thermoelectric generators, and made from semi-conductor elements which are less heavy than the conventional energy sources like batteries. The device is a prototype Zinc oxide nanowire, which extracts electrical energy simply from the change in temperature between a hot and a cold environment.

Since zinc oxide is non-toxic, the nano-generators can safely be implanted onto a human body. Inside the body, our cells produce mechanical energy by burning chemical energy that is generated through burning complex molecules of glucose into simpler ones. The nano-generators will utilise the mechanical energy and convert it into electrical energy for empowering devices inside the body.

The difference in temperature of the surrounding environment and the human body is very important in generating electricity through heat energy of the body. Since this variation in internal and external temperature is of few degrees, it would normally produce only around 200 millivolts and would not be sufficient enough to power electronic devices that normally require about 1-2 volts.

However, scientists have tried to combine a number of components in a completely new way for formulating circuits, which can function on 200 millivolts and will help in extracting heat energy from the body heat alone. Scientists also predict that in near future, temperature differences of just about 0.5 degrees will be sufficient enough to generate electricity. Some of the most capable mechanisms for inactively converting human body functions into electricity is piezoelectric effect.

The ‘Piezoelectric' substances are like ceramics which generate electricity from mechanical pull or press, and do not need any voltage to be applied on. This technique is used in ‘Heel strike' devices which generate electricity from walking. Likewise, the urine-based fuel cells are also used where one can use human excretory fluid into power.

Also, inertial energy scavenging technique is a unique type of energy gathering system. This is already being used in many Seiko watches powered by a weight system that swings with the movements of the wearer. Due to the small fraction of electrical production with these effects, there is not much hype about the electricity production of these device systems.


Project

In a nutshell, a battery uses a chemical reaction to produce an electrical current. In this experiment, we will create an electric current using nothing more than our own bodies.

1. Mount the copper and aluminum metal plates to two separate pieces of wood.
2. Connect one plate to one of the DC microammeter's terminals using an alligator clip and the hookup wire. Connect the other plate to the second terminal. A DC microammeter, which is an instrument that measures the electric current in a circuit, can be purchased from your local Radio Shack store.
3. Now place one hand on each plate.

You should see an electric current generated on the meter. If you don't see a reading then simply reverse the connections. If you still don't see a reading then you may need to clean the metal plates.

When you place your hands on the metal plates, a thin film of sweat on your hands acts just like the acid in a battery, producing a chemical reaction with the copper plate and a chemical reaction with the aluminum plate. Your hand actually takes negatively charged electrons away from the copper plate (leaving positive charges behind) and gives electrons to the aluminum plate (causing it to become negatively charged). This difference in charges produces an electrical current which flows through the meter.

1. Wet both hands.
2. Once again, place one hand on each plate.

Metals are very efficient at this electrical current we have created. Your body resists the flow of current (through the skin). When you wet your hands you greatly decrease the resistance and thus increase the current giving you a higher reading on the meter.

Parent's Note. Batterys have actually been around a lot longer than you'd think. The first practical battery was probably developed by Count Alessandro Volta, an Italian scientist, in the late 1790's. Volta's invention became known as a voltaic pile. It consisted of a stack of pairs of silver and zinc disks. The pairs were separated from one another by disks of cardboard moistened with a salt solution.

Through the years, scientists have designed smaller but increasingly powerful batteries for the growing number of portable electric devices. For example, a lithium cell is so tiny that it is often called a button battery. But it produces voltages higher than any other single cell. It uses lithium metal as the negative electrode and any one of several oxidizing agents as the positive electrode. Lithium cells are used mainly in calculators, cameras, pacemakers, and watches.

Wearable Devices

A human body constantly generates heat as a useful side effect of metabolism. However, only a part of this heat is dissipated into the ambient as a heat flow and infrared radiation, the rest of it is rejected in a form of water vapor. Furthermore, only a small fraction of the heat flow can be used in a wearer’s friendly and unobtrusive energy scavenger. (For example, nobody would accept a large device on his/her face. Therefore, the heat flow from it practically cannot be used.) At last, due to the laws of thermodynamics, the heat flow cannot be effectively converted it into electricity. However, a human being generates more than 100 W of heat; therefore, a quite useful electrical power still can be obtained using a person as a heat generator. The tool for converting heat flow into electricity is a thermoelectric generator (TEG), the heart of which is a thermopile. Typically, only a few watts of heat flow can be harvested unobtrusively on a person and thermoelectrically converted into several milliwatts in a form of electricity. If we recall that watches consume 1000 times less, it is fairly good power. Moreover, PV cells of the same area typically generate much less power because not much light is available indoors, where the authors and the reader of this paper are resting now.

The human body is not a perfect heat generator as a heat supply for a wearable TEG. The body has high thermal resistance; therefore, the heat flow is quite limited. This is explained by the fact that warm-blooded animals have received in the process of evolution a very effective thermal management. This includes a very high thermal resistance of the body at ambient temperatures below 20–25 °C if the skin temperature decreases below thermal comfort.1,2 As a result, not much heat is dissipated from the skin and only about 3–5  mW/cm2 is available indoors, on average.



1- TEG - a wireless pulse oximeter (SpO2 sensor) has been designed, fabricated, and tested on people in 2006 .The device noninvasively measures oxygen content in arterial blood. A watch-size TEG is used in this device as a power supply with a minimal power production of about 100 μW (at night) and typical variations during the day within the 100–600 μW range. A goldlike coating of the radiator provides nice appearance of the device. The coating has a high reflection coefficient in the visible region of the spectrum (to minimize heating by sunlight) and high emission coefficient in the long-wave infrared region.

2- electroencephalography (EEG) system fabricated in 2007.8,9 The main challenges in creation of such complex system powered by the wearer’s heat are lowering power consumption of biopotential readout while maintaining the signal quality and real-time data transmission. In the above example of pulse oximeter, the signal processing is performed onboard so that power consumed by the transceiver is minimal. In EEG, on the contrary, real-time brain waves should be transmitted, so the wireless link consumes large power.

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History :

1: In 2006 Vladimir Leonov and Ruud J.M. Vullers from Belgium built a working prototype of a blood oxygen sensor, or pulse oxymeter, powered with body heat. It was about the size of a watch and was successfully tested on patients. It generated about 100 microwatts while the patient was asleep and up to 600 microwatts when awake and active. The group had to design the device so it could work with a record low power of 62 microwatts vs. commercially available 10-milliwatt pulse oxymeters.

In 2007 the duo built a body-heat powered electroencephalograph device that monitored brain activity. Leonov and Vullers started by redesigning the EEG device so it consumed less power. The EEG had to wirelessly transmit real-time data to a computer, too, so it had to consume a lot more power than their first prototype.

2:Seiko's Thermic watch, which runs continuously off body heat on 1 microwatt (one-millionth of a watt). It debuted in 1998 to rave reviews, but Seiko produced only 500 units before discontinuing it.

3:In 1836, John F. Daniell, an English chemist, introduced a more efficient primary cell. The Daniell cell had two liquid electrolytes and produced a steadier current than Volta's device. In 1859, the French physicist Gaston Plante invented the first secondary battery, the lead-acid storage battery. During the 1860's, another French scientist, Georges Leclanche, invented a type of primary cell from which the modern dry cell was developed.

Use and Application

These nano-generators can be placed inside the shoe of the wearer where the heat is generated by the motion of feet, and then converted into electrical energy. The use of body energy in military is being aimed at for soldiers in battlefields using it as personal battery chargers, medical sensors, displays, gun sights, and range finders.

With the possibility of using body heat for generating electricity, scientists have found that this could be very useful in the field of medicine as well, particularly in hospitals where patients are observed round-the-clock. This includes checking pulse rate, heart rate, body temperature, blood pressure and breathing rate since it comes with a complex network of wires around the bedside, with each connection requiring its own electric supply.

Scientists can use hermo-generators for energising these complex wire systems for performing their work without creating a mess of electrical sources since they are capable of sensing the temperature variations in the body, and then collecting the heat into electrical energy.

In many fitness centres and dance clubs for example, the energy generated by the body movements of the customers was transformed into electricity and stored in a battery. This source of electricity is also being used to power the lights of the same gyms and night clubs. In fact, a Dutch environmental group is building a nightclub in Rotterdam that will have a dance floor converting vibrations from all the feet into electricity. One possible design for the floor involves piezoelectric crystals, which generate a small electric current when compressed.

Papers :

A HUMAN-BODY THERMOELECTRIC ENERGY SCAVENGING MICROSYSTEM



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