All forecasts indicate an amazing amount of sensors by the end of this decade. The range forecasted is quite wide, from a few tens of billions up to a thousand billion. Obviously, such a range tells us that it is not a forecast but an assumption of big growth. The actual number will depend on how much the cost of each sensor will decrease, how much (how little..) is the cost of embedding the sensor in the environment and in objects, how communications will be managed and how easy it will be to power them.
We are seeing progress made in each of these areas, at a pace that would indicate that higher forecast might be closer to the point.
One area where we are seeing great progress is the one of power budget: on the one hand electronics is requiring less and less power, down from mW to microW and now on to nW. At the same time we see increase in the capability to harvest energy from the environment. What is known as “scavenging”.
Researchers at the Center for Nanotechnology and Molecular Materials at Wake Forest University have developed a thermoelectric device, Power Felt, that exploit the difference of temperature on two surfaces to create an electrical current, thus transforming heat energy into electrical energy.
As shown in the figure on the left, the material is composed of three different layers, staked into a multiple fabric. Each layer consists of specific nano-polymer (red and green in the figure) separated by an insulating film. The difference in temperature on the two surfaces of the Power Felt creates a stretch in the nano polymer layers and this creates the conversion of heath into electrical energy (very similar to the conversion of mechanical energy into electrical power through the piezoelectric effect).
Now, just imagine ourselves. Our body keeps dissipating heat, hence the temperature of our skin is higher then the one of the surrounding air (or at the Equator it may be the other way around…). Now stick a square centimeter of Power Felt to your skin and you get enough power to feed a bio sensor.
Applications can be many and depending on the expected thermal difference you may create different sort of Power Felt (with a different number of layers) thus producing a variety of (micro) electrical power output.
I am pretty sure we will be seeing a growing variety of scavenging in the coming years and subtly we will see a transformation of our environment, more and more in the direction of becoming aware.