Eggshell‑Derived Powder as Reinforcement for Structures Manufactured by Digital Light Processing

Vol.:(0123456789)
In e na ional Jou nal o P ecision Enginee ing and Manu ac u ing-G een Technology (2025) 12:1737–1748
h ps://doi.o g/10.1007/s40684-025-00724-1
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REGULAR PAPER
Online ISSN 2198-0810
P in ISSN 2288-6206
Eggshell‑De i ed Powde asRein o cemen o S uc u es
Manu ac u ed byDigi al Ligh P ocessing
Te esaCa anza1· I aiaOsquila1· Ped oGue e o1,2,3· Ko odelaCaba1,2 · Ai o Tejo‑O e o1,4
Recei ed: 22 Oc obe 2024 / Re ised: 14 Feb ua y 2025 / Accep ed: 17 Feb ua y 2025 / Published online: 14 Ma ch 2025
© The Au ho (s) 2025
Abs ac
The global wa ming is a cu en challenge ha demands inno a i e solu ions in was e managemen . Eggshells, a common
was e p oduc , p esen an oppo uni y wi hin he ci cula economy. This ma e ial, when combined wi h esins, can be ans-
o med in o a aluable esou ce as a ein o cemen . In his s udy, eggshells-de i ed calcium ace a e was combined wi h a
esin and used o c ea e a iscous p in able ma e ial, allowing o he manu ac u e o samples wi h small po es and enhancing
s uc u al in eg i y. Addi ionally, X- ay di ac ion (XRD) and ene gy-dispe si e X- ay spec oscopy (EDS) con i med he
success ul in eg a ion and uni o m dis ibu ion o calcium ace a e. Fu he mo e, inc easing ela i e densi y om 50 o 75%
led o an inc ease o ha dness om 2.33 o 8.58 N, highligh ing he ele ance o he s uc u e design o ailo he mechani-
cal pe o mance o he esul ing s uc u e, wi h cohesi eness alues o 1, indica ing o al shape eco e y a e de o ma ion.
This app oach no only demons a es he e sa ili y o eggshells bu also highligh s he e ec i eness o DLP echnology o
p oduce s uc u es wi h complex geome ies. This esea ch opens new a enues o eusing disca ded ma e ials, p omo ing
sus ainable p ac ices and educing he en i onmen al impac o ou consump ion habi s.
Keywo ds Bio-based· Eggshell· 3D p in ing· Digi al ligh p ocessing
1 In oduc ion
The inc easing global popula ion is gene a ing a ising ol-
ume o was e, much o which is disca ded wi hou being
epu posed. To ackle hese challenges and p omo e sus ain-
able de elopmen , i is c ucial o explo e inno a i e ecy-
cling and euse me hods. One p omising a ea o esea ch
is he u iliza ion o ag icul u al and ood indus y by-p od-
uc s, which a e bio-based p oduc s and ypically disca ded
as was e. In pa icula , a ound 8.6 million ons o eggshell
a e p oduced e e y day, anking i as he 15 h mos pollu -
ing was e p oduc [1]. Eggshells a e p ima ily composed o
calcium ca bona e (CaCO3), a ound a 96%, 1% MgCO3, 1%
Ca3(PO4)2, and o ganic ma e [2]. The eggshells possess
no able mechanical p ope ies and a e biodeg adable, mak-
ing hem an a ac i e ma e ial o a ious applica ions, such
as biomedical applica ions [3]. Howe e , eggshell canno
be used as i is because i mus unde go h ough a p ocess
ha includes he collec ion, cleaning, g inding and sie -
ing o eggshells in o de o p oduce a ine powde . A e
ha , combining eggshell powde wi h o he ma e ials o e s
ad an ages, such as he imp o emen o mechanical p ope -
ies [4]. Fo example, Ashok e al. [5] p oduced PLA ilms
con aining 1, 2, 3, 4, and 5 w % eggshell pa icles ha ing
a size o 25μm. The addi ion o ille imp o ed he ensile
s eng h by 5.4, 25.6, 51.8, 82.1, and 33.9%, espec i ely,
while he modulus inc eased by 1.7, 24.3, 53.4, 70.5, and
20.6%, espec i ely. Addi ionally, he alo iza ion o egg-
shell con ibu es o was e educ ion and p omo es a ci cula
economy [6]. In his ega d, Flo es e al. [7] in es iga ed
a no el me hod o ob ain bio-based hyd oxyapa i e om
a esidue o eggshells. Despi e he ad an ages shown, he
* Ko o dela Caba
k[email p o ec ed]
1 BIOMAT Resea ch G oup, Escuela de Ingenie ía de
Gipuzkoa, Uni e si y o  heBasque Coun y (UPV/EHU),
20018Donos ia-SanSebas ián, Spain
2 Basque Cen e o Ma e ials (BCMa e ials), Applica ions
andNanos uc u es, UPV/EHU Science Pa k, 48940Leioa,
Spain
3 P o einma Ma e ials SL, A enida de Tolosa 72,
20018Donos ia-SanSebas ián, Spain
4 Depa men o G aphic Design andEnginee ing P ojec s,
Facul y o Enginee ing inBilbao, Uni e si y o  heBasque
Coun y (UPV/EHU), 48013Bilbao, Spain
1738 In e na ional Jou nal o P ecision Enginee ing and Manu ac u ing-G een Technology (2025) 12:1737–1748
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esea ch ca ied ou in polyme s con aining eggshell pa icle
is limi ed. The ele ance o his his wo k lies no only in he
alo iza ion o eggshells, bu also in i s ans o ma ion in o
calcium ace a e, which is soluble, acili a ing i s inco po a-
ion in o he esin o enhance he unc ional p ope ies o
he inal p oduc .
Rega ding he p ocessing o bio-based ma e ials, 3D
p in ing is a ield ha has apidly g own du ing he las
yea s in di e en sec o s such as ae onau ics, au omo i e
o medical. This echnology is based on he de elopmen
o complex 3D p in ed objec s laye -upon-laye . Among
he di e en addi i e manu ac u ing (AM) echnologies,
he e a e se en ca ego ies acco ding o ISO/ASTM 52900
S anda d [8]: Va Pho opolyme iza ion, including Digi al
Ligh P ocessing (DLP), S e eoli hog aphy (SLA), Lase -
Induced Fo wa d T ans e (LIFT), Liquid–C ys al Display
(LCD), Two-Pho on Polyme iza ion (2PP), and Volume ic
3D P in ing (V3DP); Ma e ial Ex usion, which includes
Fused Filamen Fab ica ion (FFF) and Di ec Ink W i ing
(DIW); Ma e ial Je ing (MJ); Binde Je ing (BJ); Powde
Bed Fusion (PBF), which includes Selec i e Lase Sin e ing
(SLS) and Selec i e Lase Mel ing (SLM); Di ec ed Ene gy
Deposi ion (DED); and Shee Lamina ion.
The inco po a ion o ine powde o 3D p in able sam-
ples has been ca ied ou using mainly FFF and DIW ech-
niques. Fo example, Gang e al. [9] combined i e na u-
al biomine als, including eggshell, wi h L-polylac ic acid
(PLLA) ink. Samples we e 3D p in ed by means o FFF and
showed ha he pa icle size was mainly a ound 500–900nm
and, he e o e, no block would happen since he nozzle is
410µm. Sanka a el e al. [10] combined eggshell wi h PLA
o manu ac u e 3D p in ed samples, concluding ha an
inc ease o eggshell showed an imp o emen in he mechani-
cal p ope ies. On he o he hand, Gezek e al. [11] used
DIW o de elop 3D p in ed samples based on polycap olac-
one (PCL) wi h eggshell mic opa icles, concluding ha he
inc ease in he mic opa icle con en led o a less c ys alline
s uc u e. Hemb ick-Holloman e al. [12] also de eloped
3D p in ed samples wi h he combina ion o he p e ious
ma e ial wi h eggshell and concluded wi h simila esul s o
hose o Gezek e al. [11]. Using ano he AM echnology,
SLA, Ya uz e al. [13] de eloped samples wi h eggshell a
di e en concen a ions: 1%, 3% and 5%. The bes esul s
we e ob ained wi h 1% o eggshell due o an enhancemen
in he elas ic modulus, ensile s eng h, and ha dness o he
3D p in ed composi e specimens. Rega ding o he ypes
o pa icles, Lalegani Dezaki e al. [14] demons a ed ha
inco po a ing mussel and whea pa icles in o PLA enhances
he mechanical pe o mance o 3D p in ed samples. Addi-
ionally, he combina ion o whea wi h PLA e ealed a high
shape eco e y a io. In he same line, Rezaya e al. [15]
inco po a ed i on in o PLA, imp o ing he mechanical p op-
e ies o he 3D p in ed samples.
Taking all o his in o accoun , p e ious esea ch high-
ligh s gaps in he cu en s a e-o - he-a . Al hough eggshell-
de i ed pa icles ha e been inco po a ed in o ma e ials and
used o ab ica e samples by means o AM echnologies,
he ocus has been limi ed o FFF and DIW me hods, lea -
ing o he 3D p in ing echniques o a side. Fo example,
ligh -based 3D p in ing eme ged as a powe ul oolbox o
hie a chical and complex s uc u es as hey o e supe io
esolu ion and eedom o design compa ed o nozzle-
based me hods [16]. Addi ionally, o he bes o he au ho s’
knowledge, he e a e no published pape s on he use o cal-
cium ace a e, ma e ial o be used in he p esen pape , in
he de elopmen o 3D p in ed p o o ypes. In his ega d,
calcium ace a e can be ob ained om eggshells, which a e
p ima ily composed o calcium ca bona e. By eac ing egg-
shell-de i ed calcium ca bona e wi h ace ic acid, calcium
ace a e is ob ained. This p ocess le e ages was e eggshells
as a esou ce o de eloping chemical compounds.
The main no el y o his wo k is ha explo es he po en-
ial o ligh -based 3D p in ing o ab ica e complex s uc-
u es wi h enhanced mechanical p ope ies by syn hesizing
calcium ace a e om eggshells and i s inco po a ing in o
a bio-based esin. The in eg a ion o calcium ace a e in o
he esin imp o es p in abili y and mechanical pe o mance,
demons a ing i s iabili y as a ein o cemen ma e ial.
Addi ionally, his esea ch p o ides a comp ehensi e cha -
ac e iza ion o he ma e ial, including heological beha io ,
and mechanical pe o mance o he 3D p in ed s uc u es,
highligh ing he po en ial o eggshell-de i ed calcium ace-
a e as alo ized addi i e o 3D p in ing manu ac u e.
The e o e, he aim o his pape is o show ha eggshell-
de i ed powde can be used as ein o cemen o bio-based
ma e ials p epa ed ia digi al ligh p ocessing. Fo ha ,
i s ly, an ini ial analysis o he ma e ial p in abili y is ca -
ied ou . Addi ionally, a physicochemical analysis o he
ma e ial wi h and wi hou calcium ace a e is pe o med.
A e ha , he mac o- and mic os uc u e o he 3D p in ed
samples is assessed. Finally, he mechanical p ope ies o
he 3D p in ed samples a e measu ed using ex u e p o ile
analysis and comp ession es s assays.
2 Ma e ials andMe hods
2.1 Ma e ials
The esin used in his s udy, Bio lex A10 MF Monome F ee
(BFA10MF), was supplied by 3D esyns (Ba celona, Spain).
This monome ee esin is non- oxic and biocompa ible and,
hus, sui able o biomedical applica ions. Eggshells we e
used o p epa e he esin ein o cemen . Fo ha , eggshell
powde was dissol ed in ace ic acid 1M, s i ing a 200 pm
o 2h o con e i in o calcium ace a e. A e ha , he
1739In e na ional Jou nal o P ecision Enginee ing and Manu ac u ing-G een Technology (2025) 12:1737–1748
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solu ion was le o d y a oom empe a u e and calcium
ace a e (CaAc) powde was ob ained.
2.2 P epa a ion o Mix u es
A e p epa ing he calcium ace a e, he esin was mixed
wi h 1% o calcium ace a e. This amoun was selec ed based
on p elimina y assays ha show ha highe amoun s led o
agglome a ions. The mix u e was le s i ing o e nigh o
ensu e a good dispe sion o he calcium ace a e, p e en ing
any esidue om se ling a he bo om o he lask.
2.3 Rheological Analysis
The heological assessmen s we e conduc ed using a The mo
Scien i ic Haake Rheos ess1 Rheome e (IFI S.L., Spain).
A s ainless-s eel measu ing pla e P35 (ø 35mm) was used
o all es s, wi h a 1mm gap be ween he s a iona y and
o a ing pla es. The empe a u e was main ained a 21°C,
co esponding o he p in ing empe a u e. Shea a e sweeps
anging om 0.003 o 1000 s−1 we e pe o med o analyze
he appa en iscosi y o he esin, bo h wi h and wi hou
calcium ace a e.
In addi ion, pho o heology es s we e ca ied ou wi h
A es G2 heome e (Ta Ins umen s, USA) o measu e he
apid changes in mechanical p ope ies du ing he pho opo-
lyme iza ion o pho o-c osslinkable ma e ials. The assays
we e pe o med a 21°C using 20mm diame e pla e and
0.3mm gap a 1Hz equency and 1% de o ma ion. The
moduli c osso e ime, whe e he s o age modulus (G′)
equals he loss modulus (G″), was also ob ained applying he
405nm ligh wi h 10 mW/cm2 in ensi y. S o age modulus
(G′) is a measu e o he elas ici y o a ma e ial [17] o s o ed
ene gy du ing de o ma ion, ep esen ing i s abili y o eco e
i s o iginal shape when he applied s ess is emo ed. I indi-
ca es he s i ness o he ma e ial in a iscoelas ic sys em,
wi h highe alues signi ying mo e solid-like beha iou . On
he o he hand, he loss modulus (G″) quan i ies he ene gy
dissipa ed in a iscoelas ic ma e ial du ing de o ma ion, ep-
esen ing i s iscous beha iou [17]. I indica es how much
he ma e ial lows unde s ess, wi h highe alues signi ying
g ea e ene gy loss and damping p ope ies.
The eading o he samples was s a ed wi hou ligh un il
bo h modules s abilised and 30s a e he s a o he ead-
ing he UV ligh was applied. This pa ame e is c ucial o
assessing he ansi ion o he ma e ial om a liquid o a
solid s a e du ing pho oc osslinking.
2.4 Op imiza ion o 3D P in ing P ocedu e
In his s udy, he 3D p in ed samples we e ab ica ed
using he Anycubic Pho on D2 p in e (Anycubic, China).
This p in e employs he digi al ligh p ocessing (DLP)
echnique (Fig.1A), which is a polyme iza ion p ocess
whe e a ligh sou ce (gene ally UV ligh ) cu es a pho-
opolyme esin. This me hod employs a digi al mic omi -
o de ice (DMD) con aining housands o iny, pi o ing
mi o s o accu a ely di ec UV ligh on o speci ic a eas
o he esin. Addi ionally, DLP is as e and mo e e icien
han an SLA 3D p in e , bu also allow using wide ange
o wa eleng hs.
Be o e 3D p in ing he samples, i is essen ial o pe -
o m a cu ing dep h assay. Cu e dep h is a c ucial pa am-
e e in ligh -based 3D p in ing echnologies, as i de e -
mines he exposu e ime equi ed o cu ing a speci ic laye
hickness. The p ocedu e in ol ed exposing he esin o
a ious exposu e imes o obse e he esul ing laye hick-
ness. Figu e1B illus a es he cu ing dep h assay esul s,
showing ha longe exposu e imes p oduce hicke laye s.
Addi ionally, as he cu e ime inc eases, less UV ligh can
pene a e he esin mix u e, educing he ene gy abso bed
by he uncu ed esin du ing pho opolyme iza ion.
The 3D models we e designed using MS La ice, an
open-sou ce so wa e capable o gene a ing uni o m and
g aded la ices based on iply pe iodic minimal su aces
(TPMS) [18]. Figu e1C shows he 3D models wi h 50%
(GYR50) and 75% (GYR75) densi ies, each ha ing a diam-
e e o 12mm and a heigh o 6mm. These ela i e densi-
ies we e selec ed o e alua e he in luence o po osi y on
he s uc u al and mechanical p ope ies o he 3D p in ed
samples. A 50% ela i e densi y p o ides a peanu mo -
phology o GYR50, while a 75% ela i e densi y o e s
a dense con igu a ion, wi h a smalle ci cula mo phol-
ogy o GYR75. The 3D model has he o m o a gy oid,
which is an in ini ely connec ed pe iodic minimal su ace
con aining no s aigh lines. This s uc u e is complex and,
he e o e, achie ing i s manu ac u e shows he e icacy o
no only he 3D p in able ma e ial and i s op imiza ion,
bu also he e icacy o he echnique. The digi al models
we e hen ans e ed o Anycubic Pho on Wo kshop o
apply he necessa y 3D p in ing se ings: a laye hickness
o 0.1mm (ensu ing high quali y and excellen esolu ion)
and an exposu e ime o 10s pe laye . Addi ionally, he
i s i e laye s we e o e cu ed wi h an exposu e ime o
80s o ensu e a s ong adhesion. Twel e 3D p in ed sam-
ples could be manu ac u ed a he same ime (Fig.1D) in
o de o show one o he ad an ages o his echnology:
3D p in ing op imiza ion by p in ing se e al samples a a
ime. A e p in ing, he samples we e washed wi h iso-
p opyl alcohol (IPA) and cu ed o 15min. In sum, 4 ypes
o samples we e analyzed: BFA10MF-GYR50 (wi hou
calcium ace a e and 50% ela i e densi y), BFA10MF-
GYR575 (wi hou calcium ace a e and 75% ela i e den-
si y), BFA10MF-CaAc-GYR50 (wi h calcium ace a e and
50% ela i e densi y), and BFA10MF-CaAc-GYR75 (wi h
calcium ace a e and 75% ela i e densi y).
1740 In e na ional Jou nal o P ecision Enginee ing and Manu ac u ing-G een Technology (2025) 12:1737–1748
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2.5 X‑Ray Di ac ion (XRD)
X- ay di ac ion (XRD) analysis, a powe ul analy ical ech-
nique used o de e mine he c ys allog aphic s uc u e, was
ca ied ou using a di ac ion uni (PANaly icXpe PRO).
The adia ion was gene a ed om a Cu-Kα (λ = 1.5418Å)
sou ce a 40kV and 40mA. Da a we e collec ed om 2θ
alues om 2° o 50°, whe e θ is he incidence angle o he
X- ay beam on he 3D-p in ed p oduc s.
2.6 Di e en ial Scanning Calo ime y (DSC)
Di e en ial scanning calo ime y (DSC) was pe -
o med using a DSC 822 (Me le Toledo S.A.E.). Abou
3.0 ± 0.2mg o sample we e weighed and sealed in alu-
minium pans, which we e hea ed om -50°C o 300°C
a 10°C/min unde ni ogen a mosphe e (10mL N2/min).
Fig. 1 A P epa a ion o calcium ace a e om eggshell. B Digi al ligh p ocessing 3D p in ing p ocess scheme. C Exposu e ime s hickness
plo . D Twel e 3D p in ed samples manu ac u e a he same ime. E Visual compa ison o he 3D p in ed samples wi h he digi al model
1741In e na ional Jou nal o P ecision Enginee ing and Manu ac u ing-G een Technology (2025) 12:1737–1748
1 3
2.7 Elemen al Analysis (EA) andEne gy Dispe si e
Spec oscopy (EDS)
Elemen al analysis (EA) was pe o med using a Eu o EA
Elemen al Analyse . Ca bon (C), oxygen (O) and calcium
con en was de e mined by doing a a io be ween all he
elemen s o he mix u e. Then, using he EDS is possible o
do an elemen al mapping o check he dis ibu ion o he pa -
icles h oughou he ma e ial. This was ca ied ou wi h he
esin as con ol and he esin wi h he calcium ace a e. The
main elemen s ha we e analyzed we e ca bon (C), oxygen
(O) and calcium (Ca), wi h hei co esponding pe cen age
in he esins.
2.8 Op ical Mic oscopy
Op imal images we e aken using a Nikon Eclipse E600
op ical mic oscope wi h digi al came a (Izasa Scien i ic,)
equipped wi h 10 × objec i e and 10 × eyepieces. These
images we e analyzed wi h Image J so wa e in o de o
check he po es pa e n and size.
2.9 Scanning Elec on Mic oscopy (SEM)
The su ace mo phology and he c oss-sec ion o he 3D
p in ed samples we e e alua ed by scanning elec on mic os-
copy (SEM) using a Hi achi S-4800 (Mad id, Spain) wi h an
accele a ion ol age o 5.0kV. P io o obse a ion, samples
we e moun ed on a me al s ub wi h double-sided adhesi e
ape and coa ed unde acuum wi h gold (JFC-1100) in an
a gon a mosphe e.
2.10 Mechanical P ope ies
A TA.XT.Plus C Tex u e Analyze (Aname, Mad id, Spain)
wi h a 5kg load cell was used o ob ain ex u e p o ile analy-
sis (TPA). Da a we e collec ed using comp ession es s a
1mm/s speed, 20% s ain, 5s be ween comp ession assays
( o he ex u e p o ile analysis) and 5g igge o ce wi h
a 50mm aluminum cylinde (P/50). Da a we e collec ed
and assessed using Exponen Connec 8.0.16.0 Li e so -
wa e (S able Mic o Sys ems, Godalming, UK). Ha dness
and cohesi eness we e de e mined o he ex u e p o ile
analysis.
2.11 S a is ical Analysis
The signi icance o di e ences among he samples was
de e mined by analysis o a iance (ANOVA). The analysis
was done wi h an SPSS compu e p og am (SPSS S a is ic
28.0) and Tukey’s es was used o mul iple compa isons.
Di e ences we e s a is ically signi ican a he p < 0.05 le el.
3 Resul s andDiscussion
3.1 Rheological P ope ies o  heInks
One o he mos c i ical pa ame e s o de e mining he
p in abili y o a ma e ial is i s heological pe o mance
because a low iscosi y could lead o polyme sh inkage
and oo high iscosi y could lead o agglome a ion [19]. In
his s udy, he addi ion o calcium ace a e is examined o
i s impac on he iscosi y beha io o he esin. As no ed
by Lei e de Cama go [20], highly loaded esin suspensions
exhibi non-linea beha io due o pa icula e sca e ing.
Ano he s udy ca ied ou by Cai e al. [21] in es iga ed he
e ec o he silica con en in he iscosi y o he esin and
showed ha he highe is he silica con en in he esin, he
highe is he iscosi y. This means ha he 3D p in ing p o-
cess becomes mo e di icul . The e o e, i is necessa y o
assess whe he he addi ion o 1 w % calcium ace a e a ec s
he esin’s iscosi y.
As shown in Fig.3A, he esin, wi h and wi hou cal-
cium ace a e, exhibi shea - hinning beha io , since iscosi y
dec eases wi h inc easing shea a e. Acco ding o Luo e al.
[22] and Kuhn e al. [23], he esin iscosi y o polyme ic
esins should be below 10Pa·s. In he p esen s udy, bo h
ma e ials demons a e excellen heological p ope ies sui -
able o ligh -based 3D p in ing: a a shea a e o 1 s−1, he
iscosi y is a ound 0.5Pa·s, d opping o 0.3Pa·s a a shea
a e o 100 s−1. The iscosi y o he esin used in he p esen
wo k align wi h Komissa enko e al. [24], which syn hesized
a mono-/ i-ac yla e-based slu y wi h 75 w % o zi conia,
which has a iscosi y o 1.6Pa·s a 30 s−1.
Rega ding pho o heology, wi h he addi ion o calcium
ace a e, he c osso e modulus inc eases om 32 o 120Pa
and he c osso e ime om 60 o 62s. The inco po a ion o
calcium ace a e a ec s he c osslinking p ocess, delaying he
ansi ion om liquid o solid. This obse a ion is consis en
wi h he indings o Ya ed e al. [25], who demons a ed ha
a highe solid con en in he composi ion esul s in slowe
pho ocu ing.
In e ms o G′ and G″ alues up o he c osso e poin ,
Fig.2B and C show ha bo h samples display simila pho-
o heological beha io , wi h G″ highe han G′. This signi-
ies ha bo h o mula ions exhibi a mo e luid-like beha io
un il he c osso e . Beyond his poin , he esins exhibi a
mo e solid-like beha io , as G′ is o e G″.
3.2 E alua ion o  heC ys allini y on3D P in ed
Samples
Figu e3A shows he c ys allini y o he esin wi h and
wi hou calcium ace a e. A highe peak in ensi y indica es a
highe deg ee o c ys allini y demons a ing ha he calcium

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ace a e is in eg a ed in he esin ma ix. The XRD pa e n
consis ed on a peak o bo h 3D p in ed s uc u es a 2θ = 20°.
Rega ding he mal p ope ies, Fig.3B depic s ha bo h sam-
ples show simila he mal beha io up o 200°C, whe e he
sample wi hou ace a e shows a sha p dec ease a 250°C,
while he sample wi h ace a e shows a less p onounced
dec ease ha s abilized a 250°C. Simila indings we e
epo ed in a ious s udies [26, 27]. Fo example, Ba e o
e al. [26] ca ied ou di e en DSC cu es showing ha a
highe concen a ion o calcium a ibu es a he mal s abili y.
Figu e3C shows he ene gy-dispe si e X- ay spec os-
copy (EDS) mapping, illus a ing he dis ibu ion pa e ns
Fig. 2 Rheological p ope ies. A Viscosi y–shea a e cu es. B S o age (G′) and loss (G″) modulus o BFA10MF. C S o age (G′) and loss (G″)
modulus o BFA10MF-CaAc
Fig. 3 A XRD pa e ns, B DSC cu es, And C EDS mapping o BFA10MF and BFA10MF-CaAc
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o ca bon (C), ni ogen (N), and calcium (Ca). This con i ms
he p esence o calcium ace a e in he 3D p in ed samples.
Despi e he p esence o some clus e s in ce ain a eas, EDS
elemen al mapping analysis demons a es a uni o m dis i-
bu ion o calcium h oughou he 3D p in ed sample. Table1
de ails he p opo ion o each elemen in he 3D p in ed
samples. Wu e al. [27] also ein o ced hei samples wi h
mine al compounds con aining calcium, which con ibu ed
o imp o e he ma e ial he mal p ope ies.
3.3 Cha ac e iza ion o  he3D P in ed Samples
3.3.1 Shape Fideli y
Figu e4 shows ha bo h he digi al models and he 3D
p in ed samples show simila pa e ns in e ms o he po es
size and dis ibu ion. On he one hand, bo h 3D p in ed
BFA10MF-GYR50 and BFA10MF-CaAc-GYR50 sam-
ples show he peanu mo phology. On he o he hand, bo h
BFA10MF-GYR75 and BFA10MF-CaAc-GYR75 samples
show smalle po es h oughou he su ace. As GYR50 sam-
ples ha e bigge po es, hei 3D p in ing quali y is be e
han ha o GYR75 samples since he e is less chance o
o e cu ing be ween laye s. Fu he mo e, i was obse ed
ha he addi ion o calcium ace a e did no a ec he mo -
phology and hus he shape ideli y o he samples, con i m-
ing he da a ob ained in he heological assessmen whe e
he iscosi y, cu ing ime and inal moduli (G′ and G″) we e
no signi ican ly di e en be ween he sys em wi h and wi h-
ou calcium ace a e.
The mo phology shown in Figs.4 and 5 indica es he su -
ace oughness, common o 3D p in ed samples ha do no
unde go o e a pos -p ocessing [28]. Acco ding o Sasany
e al. [29], he highe he laye heigh , he oughe he su -
ace; addi ionally 3D p in ing ime also a ec s oughness.
The e o e, bo h laye hickness and 3D p in ing ime can be
a ied o modi y he su ace mo phology.
3.3.2 Inne S uc u e
Figu e5 shows he c oss-sec ional SEM images o he
3D p in ed samples. The inne s uc u e shows he di e -
en ca i ies, bu also he di e ence be ween bo h densi ies
(GYR50 and GYR75 samples). The highe densi y led o
smalle po es and, he e o e, mo e clogging was ob ained.
On he o he hand, he po e shows hei en i e pa h h ough
GYR50 samples.
3.4 Tex u e Analysis o 3D P in ed Samples
3D p in ed samples wi h and wi hou calcium ace a e we e
analyzed using ex u al p o ile analysis, which consis ed
o wo epe i ions o uniaxial comp ession a a 20% s ain
alue wi h a eco e y ime be ween hem. Figu e6 shows he
ex u e analysis o he di e en 3D p in ed samples ega d-
ing po osi y and calcium ace a e addi ion. The i s and he
second peaks in he TPA cu e ep esen key mechanical
p ope ies o a ma e ial unde a ce ain de o ma ion. The
i s peak co esponds o he o ce equi ed o comp ess he
ma e ial du ing ini ial de o ma ion, which is a di ec meas-
u e o i s ha dness o esis ance o de o ma ion. The second
peak a ises du ing he ecomp ession phase and e lec s he
abili y o he ma e ial o eco e i s shape a e de o ma ion.
Table 1 Elemen al composi ion o BFA10MF and BFA10MF-CaAc
Sample C O Ca
BFA10MF 57.22 ± 0.91 42.78 ± 0.91 –
BFA10MF-CaAc 57.4 ± 0.91 42.38 ± 1.03 0.22 ± 0.16
Fig. 4 Su ace mo phology
images o compa ing he po e
size and dis ibu ion o he 3D
p in ed samples as a unc ion
o densi y (GYR50 and GYR75
samples). Scale ba is 250µm
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The a io o he a ea unde he second peak o he a ea unde
he i s peak, known as cohesi eness, indica es he capaci y
o he ma e ial o eco e i s o iginal o m. A cohesi eness
alue close o one sugges s ha he ma e ial nea ly ully
eco e s i s shape, demons a ing elas ic o esilien beha -
io , while lowe alues indica e pa ial eco e y o plas ic
de o ma ion.
Fi s ly, he addi ion o calcium ace a e causes an inc ease
in he ha dness. As expec ed, he highe he densi y, he
lowe he po osi y and, hence, he ha dness also inc eases.
Rega ding he cohesi eness, all 3D p in ed samples show a
o al eco e y a e he second cycle. The alues o ha dness
and cohesi eness o he 3D p in ed samples can be ound
in Table2.
3.5 Mechanical P ope ies o 3D P in ed Samples
The mechanical beha io o he 3D p in ed samples was ana-
lyzed by ca ying ou comp ession es s un il a 20% s ain.
Figu e7 shows he mechanical p ope ies o he 3D p in ed
samples (BFA10MF and BFA10MF Ca-Ac) o GYR50 and
GYR 75. On he one hand, he highe he densi y, he highe
he s eng h, since he e a e less po es. This is in conco d-
ance wi h o he s udies [30–32]. Fo example, Roohani-
Es ahani e al. [30] 3D p in ed samples wi h di e en po e
size and p in ing design leading o app oxima e po osi ies
showing ha he highe he po osi y, he so e he ma e ial.
On he o he hand, Fig.7B and D show ha he addi ion o
he calcium ace a e leads o an imp o emen in he s eng h
o he 3D p in ed samples. Fo ins ance, Lyu e al. [33] s ud-
ied he impac o calcium ace a e and showed an imp o e-
men on he mechanical p ope ies in he ange o 0–2% o
calcium ace a e. This is in line wi h Wang e al. [34] ha
s udied he in luence o calcium ace a e a a ios be ween 0
and 20%. The mechanical p ope ies we e imp o ed un il a
5% o calcium ace a e; howe e , a dec ease in he comp es-
si e s eng h was achie ed wi h alues o e 5%.
4 Conclusions
This pape p esen s he success ul de elopmen o a com-
posi e ma e ial combining a esin co e wi h calcium ace a e
de i ed om eggshells, enabling he 3D p in ing o sam-
ples ia digi al ligh p ocessing (DLP). Rheological analy-
sis demons a ed ha he composi e iscosi y was sui able
o ligh -based 3D p in ing, wi h alues in he ange o
0.3–0.5Pa·s a shea a es om 1 o 100 s−1, wi h he addi-
ion o calcium ace a e ha ing no de imen al impac on i s
low p ope ies. X- ay di ac ion (XRD) and ene gy-dispe -
si e spec oscopy (EDS) mapping con i med he success ul
in eg a ion o calcium ace a e in o he esin ma ix. The 3D
p in ed samples, manu ac u ed wi h complex geome ies,
highligh ed he po en ial o his echnology o c ea ing in i-
ca e s uc u es ha would be di icul o achie e wi h con-
en ional me hods. Fu he analysis o he ou e and inne
s uc u es o he 3D p in ed samples e ealed he p esence o
po es. In e ms o mechanical p ope ies, he s udy showed a
Fig. 5 C oss-sec ional SEM
images o he 3D p in ed
samples as a unc ion o densi y
a es (GYR50 and GYR75 sam-
ples). Scale ba is 1mm
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clea co ela ion be ween inc eased ela i e densi ies, om
50 o 75%, and enhanced mechanical pe o mance, om
2.33 o 8.58 N o ha dness alues, wi h cohesi eness al-
ues o 1 and, hus, a o al shape eco e y a e de o ma ion.
The e o e, he no el y o his wo k lies in he alo iza ion
and modi ica ion o disca ded ma e ials o acili a e he p o-
cessing o bio-based ma e ials by sus ainable p ac ices, wi h
he aim o enhancing he ma e ial p ope ies as well as con-
ibu ing o educing he en i onmen al impac .
Fig. 6 Tex u e p o ile analysis o he 3D p in ed samples o A BFA10MF-GYR50, B BFA10MF Ca-Ac-GYR50, C BFA10MF-GYR75 and D
BFA10MF Ca-Ac-GYR75
Table 2 Ha dness and cohesi eness alues ob ained by ex u e p o ile
analysis
a
, bTwo means ollowed by he same le e in he same column a e no
signi ican ly (p > 0.05) di e en h ough he Tukey’s mul iple ange
es
Densi y Sample Ha dness [N] Cohesi eness
GYR50 BFA10MF 1.92 ± 0.44a0.99 ± 0.01a
BFA10MF Ca-Ac 2.33 ± 1.11a1.02 ± 0.02a
GYR75 BFA10MF 7.58 ± 1.10b1.00 ± 0.02a
BFA10MF Ca-Ac 8.58 ± 1.61b1.01 ± 0.01a