Biodegradable Supercapacitors

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While different, Device tagging, The Internet of Things (IoT) and other tracking applications all have one thing they all need: A power source, even if for a short period or limited period.
The choices available for providing a power source include supercapacitors, electrochemical batteries or energy harvesting.


However,

they all share something in common: When they’re no longer viable -and many of these installations are shorter-term- they leave behind a power source that if not properly disposed of become waste and litter.

Designing A Supercapacitor


To fix this,
A research team at EMPA (Swiss Federal Laboratories for Materials Science and Technology) has designed a print 0n demand supercapacitors using a refitted, commercially available 3D printer along with their formula for the gelatinous inks that the printer can dispense into a substrate as a surface.


the mixture is made up of cellulose nanocrystallites and cellulose nanofibres, in addition to carbon in the form of carbon black, activated carbon and graphite.


the scientists used water, glycerin and two different alcohol types plus a pinch of table salt(for ionic conductivity) to accurately liquefy the solution and attain the required viscosity.


despite the fragile sound of the design, this non-capacitor is not a fragile, limited use component.
Able to withstand thousands of charge/discharge cycles and years of storage, even in extreme temperatures,

also resistant to shock and pressure.


Furthermore,

when it is no longer viable,

it can be left in a compost pile or simply left to nature, in just a few months, it will have degraded into harmless particles.
“was not a casual process.
it sounds easy but wasn’t at all,” says Xavier Aeby of EMPA’s Cellulose & Wood Materials lab.


“there was a long series of tests till all the parameters were correct until all the parts flowed reliably from the printer and the capacitor worked” he added,
“As Scientists, we don’t want to doddle around,
we want to understand what’s happening inside our materials.”
the supercapacitor

Multilayered Yet Not a PCB


The supercapacitor needs four layers,

which are produced by the 3D printer in sequence: a flexible substrate, a conductive layer,

the electrode, and finally the electrolyte).

The researchers used a substrate made from ink composed of cellulose nanofibrils (CNFs),

cellulose nanocrystals (CNCs), and glycerol as the base layer.

The ink for the current collector comprises graphite, carbon-black, and shellac.

The electrode ink incorporated CNFs, CNCs, glycerol, activated carbon, and graphite particles.

The ink for the electrolyte contained CNCs, glycerol,

and NaCl.
These materials were printed on top of each other onto the substrate.

They used direct-ink-writing (DIW), a printing technique in which gel ink is extruded line-by-line and layer-by-layer to form 3D objects.

The whole multilayer assembly is then folded up like a sandwich, with the electrolyte in the centre

The resulting devices supported a high capacitance of 25.6 farads/gram of active material with an operating voltage of up to 1.2 V. One was used to demonstrate a small clock.


The group also proved the capacitor’s performance over temperature and time.


To prove the bIodegradability of the construction,

they also performed decomposition tests and discovered that after only two months, the capacitor degraded, leaving only a few visible carbon particles.

Source: Advanced Materials

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