Stain­less-steel com­pon­ent boosts power out­put for bac­teria-based biobattery

Engin­eer­ing innov­a­tions gen­er­ally require long hours in the lab, with a lot of tri­al and error through exper­i­ment­a­tion before zero­ing in on the best solution.

But some­times, if you’re lucky, the answer can be right under your nose — or in this case, beneath your feet.

Bing­hamton Uni­ver­sity Pro­fess­or Seokheun ​“Sean” Choi has developed a series of bac­teria-fueled biobat­ter­ies over the past dec­ade, build­ing on what he learns to improve the next iter­a­tion. The biggest lim­it­a­tion isn’t his ima­gin­a­tion — he’s always jug­gling sev­er­al pro­jects at once — but the mater­i­als he has to work with.

When Choi — a fac­ulty mem­ber in the Thomas J. Wat­son Col­lege of Engin­eer­ing and Applied Science’s Depart­ment of Elec­tric­al and Com­puter Engin­eer­ing — needed a col­lab­or­at­or who could cre­ate a spe­cial­ized stain­less-steel com­pon­ent, he found someone just down­stairs from his office at Binghamton’s Engin­eer­ing and Sci­ence Building.

It turns out that Assist­ant Pro­fess­or Dehao Liu from Watson’s Depart­ment of Mech­an­ic­al Engin­eer­ing is an expert in laser powder bed fusion (LPBF) tech­no­logy, a new meth­od for the print­ing of stain­less-steel microarchitectures.

“LPBF is ideal for biobat­ter­ies because it enables high-pre­ci­sion, cus­tom­iz­able 3D struc­tures with com­plex geo­met­ries, essen­tial for max­im­iz­ing sur­face area and energy dens­ity,” Liu said.

They recently pub­lished a paper in the journ­al Advanced Energy & Sus­tain­ab­il­ity Research out­lining their find­ings, which could help to power small, autonom­ous devices such as sensors for the Inter­net of Things that increas­ingly con­nects everything in our lives.

Oth­er research­ers on the pro­ject are ECE Assist­ant Pro­fess­or Anwar Elhadad, PhD ​’24 (Choi’s former stu­dent); Yang ​“Lexi” Gao (his cur­rent PhD stu­dent); as well as Liu’s PhD stu­dents, Guangfa Li and Jiaqi Yang. Fund­ing the research is Choi’s 2024 grant from the Nation­al Sci­ence Foundation.

“I’m so happy about this col­lab­or­a­tion,” Choi said. ​“It makes this iter­a­tion of the biobat­tery very mean­ing­ful to me.”

How it works

Endospores provide the fuel for an elec­tro­chem­ic­al reac­tion that gen­er­ates elec­tric cur­rent. These dormant forms of bac­teria show excep­tion­al resi­li­ence from envir­on­ment­al stresses and activ­ate when con­di­tions are favorable.

The biobat­tery needs three com­pon­ents to func­tion: a pos­it­ive elec­trode (the cath­ode), a neg­at­ive elec­trode (the anode) and a mem­brane where ions exchanged between the two gen­er­ate an elec­tric cur­rent. For the best power out­put, the anode — where the bac­teria are — needs to be three-dimen­sion­al, so that the organ­isms can col­on­ize and thrive in the least amount of space.

“A two-dimen­sion­al anode is not effi­cient,” Choi said. ​“Nutri­ents will not be delivered effect­ively to the bac­teria, and their waste can­not go out effectively.”

Com­plic­at­ing the pro­duc­tion of 3D anodes is that car­bon-based or poly­mer-based mater­i­als have low elec­tric­al con­duct­iv­ity and are often too fra­gile for every­day use. Their micro­fab­ric­a­tion pro­cesses also require high tem­per­at­ures, which can be deadly to bacteria.

“Two years ago, we star­ted to use stain­less steel mesh as an anode, because its con­duct­iv­ity is really good and it’s struc­tur­ally very strong,” Choi said. ​“We were suc­cess­ful integ­rat­ing the micro­bi­al fuel cell into elec­tron­ics like this. The prob­lem with com­mer­cially avail­able mesh is that we can­not con­trol the poros­ity and rough­ness of it. We’d just buy it and then drop in bac­teri­al cells.”

The LPBF pro­cess depos­its a lay­er of met­al powder, melts and then solid­i­fies it using a laser to cre­ate a sol­id lay­er of met­al, and those two-dimen­sion­al lay­ers join up to build 3D com­pon­ents. Details for the prin­ted piece can be planned down to the nano­scop­ic level.

“We saw the poten­tial here,” Choi said. ​“Then we pre­pared oth­er com­pon­ents using 3D print­ing as well, like a seal­ing cov­er and the cath­ode part, and we simply assembled them like Lego bricks.”

The biobat­ter­ies can be stacked in series or par­al­lel to increase out­put, with six bat­ter­ies achiev­ing nearly 1 mil­li­watt — enough to power a 3.2‑inch thin-film tran­sist­or liquid crys­tal dis­play. It’s one of the highest elec­tric­al out­puts that Choi has achieved among his biobat­tery designs.

Choi noted that the stain­less-steel com­pon­ents have anoth­er advant­age: ​“You can detach the bac­teri­al cells and then reuse them, and we showed after a num­ber of uses that power levels are maintained.”

’Inspir­ing’ innovation

For Elhadad, this latest paper dir­ectly fol­lows from doc­tor­al research he did as Choi’s student.

“My PhD focused on devel­op­ing bio­elec­tron­ic sys­tems that integ­rate sus­tain­able energy-har­vest­ing tech­no­lo­gies, par­tic­u­larly micro­bi­al fuel cells,” he said. ​“This research builds on that found­a­tion by address­ing some of the key chal­lenges I encountered dur­ing my dis­ser­ta­tion — par­tic­u­larly the need for scal­able, high-per­form­ance and struc­tur­ally robust elec­trode materials.”

Elhadad added that work­ing with Choi is ​“inspir­ing and intel­lec­tu­ally stimulating.”

“He encour­ages cre­ativ­ity and pushes the bound­ar­ies of what’s pos­sible, espe­cially when it comes to integ­rat­ing bio­logy with elec­tron­ics,” he said. ​“Our col­lab­or­a­tion is very hands-on — from design­ing exper­i­ments to troubleshoot­ing mater­i­als and fab­ric­a­tion tech­niques. He has a clear vis­ion but is always open to new ideas, which made our work feel both struc­tured and innovative.”

Look­ing ahead, the Bing­hamton team would like to devise a uni­fied print­ing meth­od for the biobat­tery com­pon­ents, rather than cre­at­ing each of them sep­ar­ately. Anoth­er goal is to improve energy har­vest­ing through a power man­age­ment sys­tem to con­trol the char­ging and dis­char­ging of the bat­tery, sim­il­ar to a sol­ar cell.

The ori­gin­al pub­lic­a­tion can be found here.