Wearables get more power

(a) Typical VING structure model considered in this work and the various device configurations of the designed VINGs, including (b) without any AlN interlayer (A0), (c) with a 30-nm-thick AlN interlayer on the bottom electrode (A1), (d) with a 150-nm-thick AlN interlayer on top of the ZnO layer (A2), and (e) with a 150-nm-thick AlN interlayer sandwiched between the two ZnO layers (A3); the effective thickness for all ZnO layers in each device is 300 nm. The key design parameters for insertion of each AlN layer are layer thickness and layer position in the device structure. In terms of the AlN layer thickness, the A1 (with a thinner AlN layer) is clearly distinguished from both A2 and A3 (with a thicker AlN layer). In terms of the AlN layer position, the A1, A2, and A3 have completely different position configurations, respectively.

Wearable devices, from simple sensors to processors, prosthetics, actuators, drug dispensers will have a significant penetration in the coming years and will become, that is my take, ubiquitous to the point that we will be wearing them without even noticing them.

The weak point, so far, has been in the need for recharging the batteries of these wearables. To solve this problem there are two concurrent approaches that are being taken. On one hand the continuos decrease in power demand will lead to a longer time between recharges, on the other the progress in energy scavenging will make possible to continuously recharge the batteries.

An example of these studies is the paper published by KAIST (Korea Advanced Institute of Science and Technology) researchers reporting on a new, and more efficient way, to generate electrical power from the piezoelectric effect.

The idea is that as we move we create mechanical deformation to our dresses and these mechanical energy can be transformed in electrical energy that can be used by wearable embedded in the dress.

So far the attention has been on Zinc-oxyde for its properties of transforming mechanical energy into electrical energy over a broad spectrum of frequencies, including very low ones, like those produced by walking, as well as vibration induced by sound waves (cars noise hitting your jacket as you walk the street). 
Now KAIST scientists are reporting a new packaging where zinc-oxide layers are stacked separating the with a layer of aluminum nitride. The experiment shown a 140-200 fold increase in performance increasing the output from 7mV to 1V.

The piezoelectric chip can be embedded into fabric and used to continuously recharge the batteries of wearable devices.

Author - Roberto Saracco

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