Research: from inspiration to tangible innovation.

The inspiration

The vision behind Foam­Wood was inspired by bio­mimicry think­ing. In oth­er words, we start­ed by look­ing at nat­ur­al cel­lu­lar struc­tures to under­stand and repli­cate its ben­e­fi­cial properties.

We were par­tic­u­lar­ly inspired by wood and its cel­lu­lar, foam-like struc­tures. This inter­est was then fol­lowed by an exten­sive lab­o­ra­to­ry scale research on the flow and con­trol of foams made with bio-based par­ti­cles (NFC, fibers). Which result­ed in the Foam­Wood device: a machine that pro­duces con­tin­u­ous­ly and effi­cient­ly bio-based foams (Foam­Wood) with lit­tle cost and promis­ing appli­ca­tions.

When tak­ing a clos­er look at this very famil­iar mate­r­i­al two prop­er­ties stood out: wood’s load-bear­ing and insu­la­tion capac­i­ties. Both result from wood’s struc­tures of elon­gat­ed cells form­ing a unique large-scale struc­ture with dual prop­er­ties: in one direc­tion wood is very strong, allow­ing it to car­ry large loads, while in the oth­er, it is a good ther­mal insulator.

Also know­ing that foams pos­sess sim­i­lar cel­lu­lar struc­tures, we want­ed to explore how to cre­ate a bio-based foam with the same kind of elon­gat­ed (anisotrop­ic) struc­tures found in wood. To that end, the chal­lenge was to con­trol the aver­age foams’ bub­ble shape which tends to be spher­i­cal or hexag­o­nal as they always relax to a sym­met­ric shape once drying.

FoamWood website

The research path

The team of sci­en­tists behind the project used their exten­sive knowl­edge of the prepa­ra­tion of wet foams to start the explo­ration process. More specif­i­cal­ly, they start­ed inves­ti­gat­ing the inter­fa­cial ten­sion between the liq­uid and gas phas­es of foams.

Such explo­ration was based on the under­stand­ing of how low­er ten­sion lev­els allow the addi­tion­al sur­faces (formed by the thin films between the bub­bles) to be main­tained by the bub­ble struc­ture, which may be achieved by the addi­tion of sur­face-active mate­ri­als such as sur­fac­tants or particles.

The team also explored nov­el meth­ods to retain the shape of the bub­ble struc­ture once the liq­uid is removed from the foam; as the two most well-known meth­ods (quick oven bak­ing and freeze-dry­ing) have issues with the effi­cien­cy of the process itself and the scal­a­bil­i­ty of pro­duc­tion, respectively.

To find bet­ter solu­tions our approach focused on some pecu­liar­ly behav­ing mate­ri­als. The spe­cial rhe­o­log­i­cal prop­er­ties of these mate­ri­als allowed us to increase relax­ation time so the foam could dry while main­tain­ing the shape of the bub­bles. This nov­el process allows for scal­able and flex­i­ble pro­duc­tion of such foam mate­ri­als nev­er accom­plished before. Through Opti­cal Coher­ence Tomog­ra­phy (OCT), Scan­ning Elec­tron Microscopy (SEM), and mechan­i­cal test­ing we have con­firmed that our method can pro­duce anisotrop­ic foams. Not to men­tion, our process may also be tuned in such a way that the nec­es­sary shrink­age occur­ring dur­ing the dry­ing process favors a cer­tain direc­tion, fur­ther enhanc­ing the anisotropy.

To know more check the links below.

Novelty

Years of research then result­ed in the main inno­va­tion behind this project: the Foam­Wood man­u­fac­tur­ing con­tin­u­ous process. It can be adjust­ed to cus­tomer-defined para­me­ters to pro­duce bio-based anisotrop­ic foams made of read­i­ly avail­able mate­ri­als and min­i­mize the amount of raw mate­r­i­al. 

FoamWood website

The device

The Foam­Wood process was designed in mod­ules. Each of them can be cus­tomized sep­a­rate­ly to best fit cus­tomers pro­duc­tion vol­umes and needs. The more foam noz­zles a device has, the larg­er are the foam vol­umes it can pro­duce. Con­se­quent­ly, the sizes of the oth­er mod­ules must be adjust­ed to fit the pro­duc­tion vol­ume. The sim­plic­i­ty and mod­u­lar­i­ty of this method make it also suit­able for decen­tral­ized production.

FoamWood website
FoamWood website

The foam

A key aspect of the inno­va­tion is the use of a cel­lu­lose based car­ri­er flu­id which acts as a binder and a mould to cre­ate anisotrop­ic rod-like struc­tures. One of the most inter­est­ing effects of the car­ri­er flu­id is the reduc­tion of the ener­gy con­sump­tion dur­ing the dry­ing process. Inde­pen­dent of the addi­tives the ener­gy need­ed for water removal is sig­nif­i­cant­ly reduced, espe­cial­ly if com­pared to oth­er foam form­ing processes.

The Foam­Wood method can pro­duce a vari­ety of foams using dif­fer­ent raw mate­ri­als and set­tings, each result­ing in a dif­fer­ent set of prop­er­ties. At this point we con­clude that almost any fiber based raw mate­r­i­al that cre­ates a net­work struc­ture can be used with our method. Still, among the suit­able foam mix­es we believe the most inter­est­ing ones to be made ful­ly with bio-based (and biodegrad­able) non-tox­ic ingre­di­ents. Nonethe­less, we keep our eyes open for new mate­ri­als and appli­ca­tions such as con­duc­tive car­bon and suit­able bat­tery tech­nol­o­gy appli­ca­tions. 

Results

The Foam­Wood new con­tin­u­ous method pro­duces foams with elon­gat­ed and closed bub­bles struc­tures, which cre­ate an anisotrop­ic film struc­ture. Such char­ac­ter­is­tics give the final mate­r­i­al high direc­tion­al strength and insu­lat­ing and shock proof­ing prop­er­ties.  

As a result, Foam­Wood has a supe­ri­or direc­tion­al strength (per den­si­ty) in com­par­i­son to oth­er bio-based foams. Due to the material’s elon­gat­ed bub­bles our foams are hard­er and stronger even if com­pared to cardboard.

Like wood,
our research shows
that FoamWood presents
great load-bearing strength
in one direction and
great thermal insulation
on the other.

FoamWood website

Our team got to under­stand well how Foam­Wood behaves as a mate­r­i­al.  By exam­in­ing the foam struc­ture using Opti­cal Coher­ence Tomog­ra­phy (OCT) and Scan­ning Elec­tron Microscopy (SEM) we could con­firm an aver­age 1:2 aspect ratio between the length of the bub­bles on the stronger direc­tion and the insu­lat­ing direc­tion, con­firm­ing the anisotropy of Foam­Wood.  

And through com­pres­sion and acoustic emis­sion (AE) exper­i­ments, we con­firmed that along the elon­gat­ed bub­bles’ direc­tion the strength was up to 64 times high­er than the oth­er direc­tion. The strength dif­fer­ence between the ori­en­ta­tions is sig­nif­i­cant­ly larg­er by a fac­tor of 10 than oth­er anisotrop­ic cel­lu­lose foams. 

To learn more about our research results, please check the sci­en­tif­ic arti­cles below: 

From © The Roy­al Soci­ety of Chem­istry 2020:
Crossover from mean-field com­pres­sion to col­lec­tive phe­nom­e­na in low-den­si­ty foam-formed fiber material