Transcript Document

ENERGY HARVESTING THROUGH
REVERSE
ELECTROWETTING
-VINUTHNA C.R
DEBOLINA SAHA
Indian Institute of Technology
Hyderabad
Electrowetting
Electrowetting is a microfluidic phenomenon that
changes the surface tension of the liquid on the solid
surface on application of voltage.
Electrowetting on dielectric(EWOD) –
 Liquid spreading on the dielectric surface is facilitated
by electrically induced increase in the dielectric
surface wettability.
 Motion of a conductive liquid on a dielectric-coated
conductive substrate.
 Wettability change arises from the extra electrostatic
energy that is associated with electrically charged
liquid-solid interface.
Surface Energy
Wiki definition: Surface energy may be defined as the
excess energy at the surface of the material compared
to the bulk.
 ρ(sl effective)= ρ(sl0) – 1/2CV^2
 cosϴ=cosϴ0 + 1/2CV^2
Contact angle
The contact angle is the angle measured through the liquid,
where a liquid/vapour interface meets a solid surface.
REVERSE ELECTROWETTING
Converting mechanical energy of liquid motion into
electrical current, thus achieving reverse electrowetting
(REWOD).
Constant bias voltage between droplet and electrode
External mechanical actuation - moves the droplet to
force the decrease of its overlap with the di-electric film
coated electrode
Tom Krupenkin and Ashley Taylor
Converts pressure energy into electrical energy
Liquid metal alloy- Galinstan
Instep Nano power- research
Basic concept - Change in contact angle and surface
energy
How this works ?
Capacitance(C) = € A/d
Cmax----->Cmin because of change in effective contact
area.
0
How to make it efficient?
More energy is generated when the conductivity of the fluid is
more
Electrode material of low conductivity is preferable
Using more droplets thereby increasing the effective contact
area
Making the channel length more
Challenges….
Energy produced is very less
Device manufacturing for practical purposes
“Footfalls for phone calls”
When we walk our body produces 40 watts of mechanical power
as heat when our feet strike the ground.
A special electricity-generating cushion placed inside the soles of
a regular pair of shoes can transform some of that footfall power
into several watts of electricity.
 Over the course of a single day, the generated energy, which gets
stored in a small battery in the sole, provides enough electricity for
a pedestrian to extend her smartphone’s battery life