scientists create a tiny battery for the smallest computers.

There was a time, not so long ago, when com­put­ers were so large that they took up entire rooms. Today, some pro­cess­ing units can be as small as a few grains of dust.

Even next to a grain of rice, those microm­e­ter-sized chip stacks seem infinitesimal.

Shrink­ing com­put­er bat­ter­ies to fit this size, how­ev­er, has proven more difficult.

With lit­tle room for stor­age, small­er com­put­ers must rely on ultra­son­ic or pho­to­volta­ic cells to con­tin­u­ous­ly recharge the micro­bat­ter­ies with ener­gy from vibra­tions or sun­light. This has its draw­backs, as the com­put­er will not work with­out a con­stant pow­er sup­ply or in dark places like the human body.

Some sci­en­tists in Europe there­fore pro­pose an alter­na­tive struc­ture: a micro­bat­tery based on fold­ing thin micro-lay­ers like origami.

The bat­tery is only a pro­to­type for now, but pre­lim­i­nary results are encouraging.

“There is a des­per­ate need to devel­op high-per­for­mance bat­ter­ies for the mil­lime­ter and sub­mil­lime­ter size regime, as such ener­gy stor­age sys­tems would facil­i­tate the devel­op­ment of tru­ly autonomous microsys­tems,” the authors write.

Full-size com­put­er bat­ter­ies are typ­i­cal­ly based on “wet chem­istry,” which means that elec­tri­cal­ly con­duc­tive met­al sheets are placed in con­tact with liq­uid elec­trolytes to cre­ate ener­gy flow.

Chip-based bat­ter­ies of a cer­tain size, how­ev­er, can­not han­dle liq­uid electrolytes.

So the inven­tors of this new micro­bat­tery pressed a sol­id elec­trolyte between two microchips that are paint­ed with a super-thin film of elec­trodes, one pos­i­tive, one negative.

This sol­id elec­trolyte, how­ev­er, is not as effec­tive as using a liq­uid elec­trolyte, where fold­ing comes into play.

By rolling a flat bat­tery stack into a “Swiss roll cylin­der,” sci­en­tists can squeeze much more sur­face area into a small space. That’s actu­al­ly how the cylin­dri­cal cells in Tes­la’s elec­tric cars work.

At the scale of a cubic mil­lime­ter, it is extreme­ly dif­fi­cult to roll thin, brit­tle mate­ri­als into this type of shape via exter­nal pressure.

For­tu­nate­ly, there is anoth­er way to bend the mate­r­i­al on its own, and it’s called “micro-origa­mi.”

The tech­nique works like a roller blind. As the thin mate­r­i­al is pulled down, you can let go of that mechan­i­cal ten­sion and it will soar and roll into a cylinder.

On a chip, the researchers were able to achieve this move­ment by attach­ing one side of the thin mate­r­i­al to cre­ate, essen­tial­ly, the bar of a blind.

Ulti­mate­ly, the team was able to roll a pro­to­type micro­bat­tery into an area of just 0.04 square mil­lime­ters, offer­ing eight times the capac­i­ty of what a sim­i­lar-sized flat bat­tery could achieve.

The authors say the cylin­der resem­bles the stan­dard Swiss roll struc­ture used in larg­er bat­ter­ies, includ­ing at least two col­lec­tor lay­ers, a cath­ode film, an anode film and an elec­trolyte film all wound together.

Not only is the design recharge­able, but the researchers say the bat­tery as it is could pow­er the small­est com­put­ers we have for about 10 hours. And there’s still work to be done.

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