Biomimicking of Hierarchal Molluscan Shell Structure Via Layer by

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Bioengineering

Biomimicking of Hierarchal Molluscan Shell Structure Via Layer by Layer 3D Printing Ramdayal Yadav, Rajendra Goud, Abhishek Dutta, Xungai Wang, Minoo Naebe, and Balasubramanian Kandasubramanian Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.8b01738 • Publication Date (Web): 23 Jul 2018 Downloaded from http://pubs.acs.org on July 23, 2018

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Industrial & Engineering Chemistry Research

Biomimicking of Hierarchal Molluscan Shell Structure Via Layer by Layer 3D Printing Ramdayal Yadava, Rajendra Goudb, Abhishek Duttac, Xungai Wanga, Minoo Naebea, Balasubramanian Kandasubramanianb* a

Institute for Frontier Materials, Deakin University, Waurn Ponds VIC 3216, Australia b

Rapid Prototyping Lab, Department of Materials Engineering, Defence Institute of

Advanced Technology (DU), Ministry of Defence, Girinagar, Pune-411025, India c

Dow Chemical Co., Core Research and Development, Midland, MI 48674, United States

*Corresponding Authors Email: [email protected] and [email protected] Tel: 020-24304207 / Fax: 020-24388835

Abstract Nature armours possesses remarkable mechanical properties which renders ingenious combination of strength and toughness by the virtue of hierarchical layered microstructure composed of mineral tablets, interleaved with organic biomaterials. Here we have demonstrated the unified approach for elucidating the effect of architectural design and its parameter on the mechanical property of dimensionally controlled 3D prototyping of Poly (acrylonitrile-co-butadiene-co-styrene) tri block Copolymer.

The manipulation of tablet

orientation, tailoring the site-specific positions and interfacially fused interlocks possess the ability to augment the mechanical characteristics of the material. Therefore, it has been observed that the bulk property of printed ABS sample mainly depends on type of molluscan shell architecture. For instance, an enhancement in impact (20%) and wear properties (friction constant=0.50, wear rate 0.00012 mm3/Nm) was observed for crossed laminar

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aragonites compared to the other hierarchical structures. In this work, we have demonstrated the possibility of utilizing naturally available molluscan shell design to alter the mechanical property of 3D printed ABS. Key word: Molluscan Structure, fused deposition modeling, layer by layer deposition, Poly (acrylonitrile-co-butadiene-co-styrene) tri block Copolymer

1. Introduction The interdigitating architecture of natural materials like shells renders superior mechanical properties via exquisitely organized1-2, yet heterogeneous, reinforcing particles and building blocks3-5. The reinforcement of hierarchal natural materials invokes complex structure and cellular articulates that limits the possibility of manufacturing such structure in synthetic systems6. In contrast to conventional methods like freeze drying7, layer by layer deposition, electrophoric deposition, Dimas et al. utilized 3D printing technique for mimicking staggered composite by utilizing VeroWhite Plus and TangoBlack Plus and further demonstrated 20% augmentation in mechanical properties compared to its constituents8. 3D printing offers manipulation of personally tailored materials with high degree of reproducibility and sustainability. In this context, Barthelet et al. illustrated that the arrangement of interdigitating arrays in nacreous structure acquires Voronoi pattern where the shifted sites mimic staggered composite laminates9-10. Further, P. Trans et al. employed the Voronoi pattern for 3D printing of nacreous structure via layer-by-layer fusion of ABS as polygonal tablet with poly lactic acid and thermoplastic polyurethane as interfacial biomaterials and subsequently, demonstrating the failure mechanism for brick and mortar complex architecture of nacre11-12. Though, the rapid prototyping technique evolves as a proficient methodology for printing complex biological exoskeleton and elaborating their failure mechanism under the tensile, compressive and fatigue loading but exploration of other


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shell structures like crossed laminar, complex crossed laminar, foliated calcite etc. are yet to be explored. Balasubramanian K et al. have demonstrated in their extensive literature review on mollusc architecture especially nacreous staggered design strategies that though various processing methods like conventional bulk material technique, freeze casting, layer by layer deposition and self-assembly etc. are some extensively exploited technique to mimic biological exoskeleton in artificial materials. But every methodology has advantages as well as some implication to render proficient emulation of biological architecture as elucidated in table 1 and the advent of 3D printing can enable on-demand, rapid prototyping of such intricacies in variety of range of materials11. Table1. Comparative analysis various methodology to fabricate Nacreous structure (Adapted as per the copyright permission guidelines from ACS Industrial and Engineering Chemistry Research: Ramdayal Yadav et al. Review on 3D Prototyping of Damage Tolerant Interdigitating Brick Arrays of Nacre, Eng. Chem. Res., 2017, 56 (38), 10516–1052511) Synthesis Technique

Advantages

Disadvantages

Conventional Bulk

Simple, large scale

Larger Layer thickness

materials

production

(~100µm)

Freeze Casting

Controlled interface

Energy consuming method

behaviour with variety of

Mineral volume fractions

materials, Bulk materials

are not equivalent to Nacre

production with high

composition

toughness, Controlled

Difficult control the

thickness

segmented overlap minerals

Layer by Layer Deposition

Controlled thickness with

Time consuming method

nano dimension,

Scaling is difficult,

Comparative loading of

Reduced mechanical

mineral phase, Ability to

properties at higher



fabricate homogeneous

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concentration

film Self-Assembly

Possibility of molecular

Difficult to scaled

level assembly, Bulk layer

fabrication

materials 3D printing

Rapid production, printing

Printing of limited number

of complex structure, On

of materials, inability to

demand printing,

combine nanoscale printing

Possibility of structural

with macroscale design,

customization,

Control over surface

Ability to print various

quality

biological inspired architecture with higher mineral concentration, Utilized as efficient predictive tool for improved synthetic materials

In this article, we have demonstrated the 3D printing of site specific, layer-by -layer fusion of in-situ Poly (acrylonitrile-co-butadiene-co-styrene) tri block Copolymer fibers. It is widely known that mechanical properties of nacre are far superior to its constituents13-15. Wegst et al. have demonstrated that bone and nacre comprise of meagre constituents, but the resulting composites render superior properties in terms of their mechanical attributes as elucidated in fig 116.


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Fig 1. Mechanical attributes of various bio-mimicked systems The current investigation attempts to explore the mechanical response and wear properties of various mollusc architecture. We have further elucidated that cross laminar structure rendered long range topological interlocking during the high-temperature fusing stimulus compared to the short-range interlocks in nacreous interdigitating architecture. The field emission scanning electron micrograph (FESEM) of fractured surface of the complex crossed laminar structure revealed that crack propagation was arrested via fused interfacial zone. 2. Experimental Technique and processing method 2.1 Materials Acrylonitrile Butadiene Styrene (ABS) (High flow, medium impact Absolac 920, MFI ˃27 at 220 °C/10 kg; Density 1040kg/m³; Linear Mold Shrinkage of 0.3 to 0.5%.; Vicat softening temperature-98⁰C). 2.2 Printing Process



ABS pellets were dried in a vacuum oven for 4 h at 115°C for removing moisture and other volatiles. The spools of ABS with 1.75mm diameter were fabricated by LabTech single screw extruder (Thailand) as illustrated in fig 2. To fabricate structural intricacies of shell attributes, we have utilized in-situ fiber extrusion of ABS fibers of controlled diameter followed by layer-by-layer fusion via fused deposition technique (Indicbot, India) as illustrated in fig 2. The printing parameters and characterization technique have been demonstrated in table 2.

Fig 2. Schematic representation of processing of various shell structure Table 2. Printing condition and various characterization technique for evaluating mechanical and microstructural properties of printed sample Printing condition Temperature

Nozzle Temperature-280ºC Bed Temperature-90ºC

Print Speed

40 mm/s


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Travel Speed

150 mm/s

Infill Density

100%

Layer Height

0.1mm

Flow Rate

70%

Size of Object

ASTM D256 for Impact, ASTM D638 for Tensile

Filament diameter

1.75mm

2.3 Characterization Technique Microstructural analysis of the printed ABS samples were characterized via field emission scanning electron microscope (Carl Zeiss AG, Germany). Impact analysis of the samples were carried out by notched Izod impact technique (as per the ASTM standard D256; Tinius Olsen, USA; Model Impact 503 tester at a single – edge notch angle of 45⁰ ± 1⁰ with a notch radius of 0.25 mm and depth of 2.54 mm). The wear attributes of the developed samples were analyzed by pin on disc friction and wear rig (Magnum engineers, Bangalore). The sliding distance of 25.13m with constant sliding speed of 0.418m/s, load of 9.8N, track radius of 16 at 50rpm for about 5 minutes has been employed for the wear test for 27X10X6mm dimension specimen. The tensile strength of the printed ABS sample was carried out as per the ASTM standard D638 type IV by utilizing custom developed stressstrain setup at a strain rate of 12µm/sec. 2.4 Design Details and Printing of Mollusc Shells: Microstructure of highly oriented invertebrate shells elucidate either one axis, parallel gastropod nacre, columnar calcite of bivalves, fibrous layer of brachiopods or a sheet texture (bivalve nacre, foliated, cross laminar microstructure)17. The patterned feature and complexity of mollusc shell are basically categorized into various morphological structures including simple prismatic, nacreous foliated, composite prismatic and crossed lamellar



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structure as illustrated in fig 3. Kobayashi et. al. have coined only three different shell type: the nacreous, foliated and crossed lamellar based on the distribution survey of bivalves18. The structural details of the nacreous, foliated and crossed lamellar structure have been provided in table 35, 19-24.

Fig 3. Schematic illustration of various printed mollusc architecture (a) Nacreous Structure (b) Foliated Structure (c) Cross Lamellar (d) Complex Cross Lamellar Table 3. Structural details of mollusc architecture. Shell Type

Structural Architecture

Dimensional Details

Crystal Aragonite or Calcite

Nacreous

Tablet

shape

aragonite Thickness-0.4-3 µm

crystals arranged in brick Width- 5 to 10µm and wall configuration

Length- 2-10 µm


Aragonite

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Foliated

Long lathe like calcite Thickness-0.2-0.5 µm

Calcite

crystals arranged in side to Width- 2 to 4 µm side

contact

overlapping sheets

in Length- 20 µm Main face consists of 10-18 faces of coincide foliated sheets

Cross Lamellar

Lamellar arrangement like Width- 5 µm plywood

Complex

Aragonite

Length- 20 µm

Intergrowth of aragonite Similar configuration like cross Aragonite

Crossed lamellar needles

lamellar but having intergrowth blocks of crystallites arranged with four principal orientation

It is widely acknowledged that the mollusc shell encompasses mineral phases intercalated between hydrated organic biopolymer and an example of phenomenal growth mechanism which starts with formation of macro structure followed by micro and nano elemental growth in shell5. Mineral phase available alone in shell structure cannot render high strength and toughness due to its inherent brittle attributes. However, when it is combined with organic layer as well as micro and macro structure, results in outstanding mechanical properties. Shell microstructures are characteristics of calcite (i.e. prismatic, foliated) and aragonite (i.e. nacre, cross lamellar) where calcite possesses rhombohedral crystal structure and aragonite consists of orthorhombic crystal structure. As illustrated earlier, nacreous architecture contains tablet shaped arrangement in brick and wall configuration (Fig 4 a) while foliated microstructures are also layered architecture but they contain blade like lathes. These blades are developed by the virtue of advancement in front growth and sometime truncated in lateral direction. The design strategy for the complex cross lamellar structure



(CCL) was emanated from fig 4 (b), which is exemplified as the most common architecture (~90% of gastropod and ~ 60% of bivalve) among all reported interdigitating arrays of mollusc family. In contrast to nacreous and foliated architecture, cross lamellar structures consist of three macrolayers i.e. inner layer, medium layer and outer layer, stacked in 0⁰/90⁰/0⁰ directions. Each macroscopic layer consists of first, second and third order lamellar and all these successive layers are arranged in tessellated pattern5. The first lamellar structures are oriented at 35⁰-40⁰ with respect to each other that encompasses thin long stacks of second order lamellar with single crystal of third lamellae. The complex crossed lamellar structure is analogous to previous architecture (cross lamella) in inner and middle layer but outer layer composed of fibrous/block and porous structure with nanoscale particulates (~100 nm)25.

Fig 4 Schematic illustration of (a) nacreous architecture (b) cross lamellar structure (Fig 4 (a) is (Adapted as per the copyright permission guidelines from ACS Industrial and Engineering Chemistry Research: Ramdayal Yadav et al. Review on 3D Prototyping of Damage Tolerant Interdigitating Brick Arrays of Nacre, Eng. Chem. Res., 2017, 56 (38), 10516–1052511))


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To imitate the complex staggered microstructure, we have utilized fused deposition modeling technique which possesses the ability to print application specific complex architecture with reduced processing cycle and time. It is widely acknowledged that the naturally available designs are complex architecture that involves macro, micro and nano level hierarchical intricacies and printing such design in artificial materials is still a great challenge in currently available 3D printing technology. But some scientific reports like B.G. Compton et al. elucidated the printing of balsa wood by fiber reinforced epoxy26. K. Sanderson advocated 3D printing technology and quoted that “capturing the intricacies of bone and nacre in one step is complicated but simultaneously he anticipated that the advent of three-dimensional printing would open a new avenue to address such challenges which in theory possess the ability to print any artefact”27. Although, sincere efforts have been employed to incorporate mineral dimensions and their intricacies involved in mollusc structures during CATIA design but we believe that dimensional changes occurred when designs were converted into standard tessellation language (.stl) for printing. Therefore, it is essential to illustrate that this work involves the imitation of mineral orientation in various shell structure without considering the utilization of organic biopolymers and micro and nano configuration beyond 25µm (optimum resolution of printing machine). It should be also noted that this work emulates the micro level dimensionality of mollusc architecture instead of exploiting its nano intricacies in the structure. 3. Results and Discussions Prior to the fabrication process, the samples for impact testing were created as per ASTM standard D256 via CATIA software (Supporting Information 1) followed by converting the structure in standard tessellated language for fused deposition 3D printing



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technique. The remarkable combination of mechanical properties of mollusc shells are attributed to the number of mechanisms including presence of voids, nanoasperitiescontrolled sliding, interlocking of nanoasperties, weak organic interface, interlamellar mineral bridges multiple crack and large crack bridging1,

4, 28-30

. F. Brathelate et al. have

elucidated that nature firmly controls size, shape and constituent block arrangement in nacre which is widely referred as architectural arrangements of building blocks31-33. The diversified properties of mollusc exoskeleton have been obtained by the virtue of such architectural arrangement of limited set of ‘universal’ motifs at distinct and multiple length scale31. In addition to that, the mechanical attributes (deformation and fracture) are governed by their interface which occupies small volume fraction in the material9, 15, 34-35. It has been observed that dehydrating the organic interface turns nacre into a brittle material in contrast to its quasi-ductile composite characteristics9.

The remarkable combination of mechanical

properties of mollusc shells are attributed to the number of mechanisms including presence of voids, nanoasperities-controlled sliding, interlocking of nanoasperties, weak organic interface, interlamellar mineral bridges multiple crack and large crack bridging28-30,

36

.

Therefore, in this study we have demonstrated the effect of varying microstructural architecture and their interfacial interlocks on mechanical characteristics of ABS. In order to deduce the mechanical properties of ABS, it is essential to glean the printing mechanism of fused deposition modelling since the attributes of printed parts are largely governed by the number of parameters elucidated in table 2. It has been observed that fused deposition modelling primarily mechanize the printing process by interlayer coalescence (between layers) and intralayer coalescence (between track) and even the coalescence of the track themselves37. Faes et al. have reported that coalescence of the layer occurs through the process of contact, wetting and neck growth with subsequent diffusion of thermal driven molten viscous polymeric materials37. The property of the printing parts is


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primarily a function of printing condition, thermal condition, heat capacity and the thermal history of the materials but N. Aliheidari et al. have exemplified that 3D printing lead to the reduced overall density by the virtue of printed offset layer, therefore, relative density (ratio of bulk density with respect to filament bulk density) may provide significant attributes regarding the mechanical properties of printed sample38. In this context, we have demonstrated the relative density of printed sample for ABS as delineated in table 4. It has been observed that in our study the relative density is independent to the design strategies for ABS sample but the marginal alteration in bulk relative density can be associated to the lower thermal expansion ratio and shrinkage ratio. Table 4. Relative Density of Printed Design Strategies Mollusc Design

ABS

Pristine

0.96

Nacre

0.95

Foliated

0.95

Cross Lamellar

0.94

Complex cross lamellar

0.96

The fracture characteristics of printed sample, the cross section of printed fractured microstructure of biological exoskeleton of ABS samples have been shown in fig 5 (a)-(d). It has been extensively reported that the failure process in glassy polymers largely depends on microscopic (Crazing or shear banding) or macroscopic (necking) flow and it dissipates the localized stress via bond rupture, cavitation, crazing, viscoelastic deformation and crack growth prior to catastrophic failure of the material. The micrographical analysis of fractured ABS samples have demonstrated their characteristic failure mechanism fracture mechanics



i.e. shear deformation mechanism and multiple crazing39 in addition to the interlayer raster delamination. R Lach et al. have exemplified that the shear deformation mechanism of ABS involves the cavitation of rubber particles and exhibits its dominance close to the crack where higher temperature and lower stresses are observed40. While, multiple crazing is far from the crack where the stress level in equatorial region in rubber particles must be high enough to initiate the plastic deformation. It is envisioned that though the crack propagation phenomenon differs in all mollusc structures but the appearance of the fractured surface possesses the effect of shear deformation and multiple crazing mechanisms.

Fig 5. 3D printed microstructure of (a) Nacre (b) Foliated (c) Cross Lamellar (d) Complex cross lamellar 3D printed nacreous architecture demonstrated the formation of non-regular cocontiguity between the layers of ABS samples but such local imperfection in the structure do


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not relinquish any compromise in the impact property compared to the pristine printed ABS sample. As stated earlier the energy dissipation during the crack advancement in mollusc structure follows various methodologies but F. Barthelat9 illustrated that the nacreous structure exhibits “stress whitening” phenomenon which is also referred as “process zone” in the fracture mechanics and such appearance of the fracture surface is analogous to the crazing in the polymeric systems41. The fractured surface of nacre structure illustrated the formation of tearing type of surface as delineated in fig 6 (a) which has been coined as ductile failure phenomenon by K.R. Hart et al.42. Whereas, foliated articulated architecture exhibited the characteristic failure mechanism of bulk ABS polymeric system which involves the presence of cavitation and crazing phenomenon, but the fracture surface of foliated structure elucidated the prevalence of crazing phenomenon of plastic deformation. The fracture surface of complex crossed lamellar architecture elucidated the formation of micro patches which evolve through the regular jumping of cracks at the fracture surface and hence rendered optimum impact property compared to other articulated structure as delineated in fig 6. It is evident from the fracture topology that under the external loading stimulus the interfacial debonding was not observed and the crack propagation and dissipation of energy presumably occurred due to the intra-layer fracture and crack delocalization43-48. We apparently affirm that though we have explained the possibility of fracture phenomenon in printed biological exoskeleton structure, but it requires further detailed architectural analysis for comprehensive delineation of its surface manifestation after fracture.



Fig 6 Fracture surface of (a) Nacre (b) Foliated (c) Cross Lamellar (d) Complex cross lamellar It has been observed that Nacreous structure demonstrate optimum compressive strength and tensile strength while crossed lamellar microstructure has been contemplated for highest fracture toughness47. Fig 7 (a) and (b) elucidates analogous characteristics of the developed composite where the strength of the nacre system was contemplated to be the highest in addition to the maximum toughness for complex crossed lamellar structure compare to pristine ABS sample (Table 5). It is well documented that the biologically available nacreous structure contains nano to macro hierarchy in addition to organic biopolymer which tremendously augments its mechanical strength. Since, the printed nacreous design does not contain either nano hierarchy or organic biopolymer therefore, the mechanical strength would be the function of tablet orientation and their configuration.


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Weiner et al. have demonstrated that the unique tessellated architecture of cross lamellar structure is responsible for delocalization of larger crack which leads to crack splitting when it reaches to inner macrolayer49. The 0⁰/90⁰/0⁰ configuration of cross lamellar structure arrest the easy-to-form crack and further improves its toughness under the application load. The multilayer architecture in such design strategies provides multiple energy dissipation point and delocalization occurs in the form of crack bridging, crack branching, multiple channel crack and delamination cracking. In this context, the improved toughness of complex cross lamellar could be related to two energy dissipation mechanism i.e. tunneling of multiple crack and crack bridging and the orientation of second order lamellae at ±45⁰ can be attributed to the bifurcation the crack at the interface. Kamat et al. demonstrated the cohesive law of the crack bridging model based on micromechanical model as elucidated in eq. 143-44

σ (∆u ) = β ∆u 2 …….1 Where σ = Traction on the crack surface; u = Crack opening displacement β =Effective parameters that incorporates all the possible energy dissipation mechanism. Based on the theoretical model Kamat et al. equated propagation phenomenon in cross lamellar architecture to non-catastrophic Aveston-Cooper-Kelly limit where all bridging ligaments are hypothesized along the crack wakes43-44. In this context, the proposed model describes that the combination of multiple cracking and their further bridging enhances the fracture characteristics of developed microstructure as illustrated in fig 6. It has been also noticed that the crack growing along 450 of first order lamella renders the additional augmented mechanical properties39-41.



Fig 7. The mechanical attributes of various architecture (a) Impact properties of various architecture printed for ABS (b) Tensile properties of printed architecture for ABS Table 5. Mechanical attributes of various designed Mollusc shell Elastic Modulus

Toughness (J/mm3)

Shell Structure

(MPa)

Pristine ABS

15.64±0.35

0.268±0.021

Nacre

19.66±0.33

0.248±0.065

Foliated

17.76±0.30

0.23±0.028

Cross Lamellar

7.5±0.41

0.386±0.064

Complex Cross

19.42±0.39

0.196±0.022

Lamellar


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Wear is complex phenomenon and defined by organization for economic cooperation and development (OECD) as “the progressive loss of substance from the operating surface of a body, occurring as a result of relative motion at the surface”. Wear involves complicated combination of phenomenon of adhesion and transfer, abrasion or cutting, plastic deformation, fatigue, surface fracture, tearing and melting50. In this study, we have exploited the utilization of pin on disc arrangement which evaluate the adhesive wear developed by the frictional motion between the surface of large circular disc and end of the pin as elucidated in fig 850. The adhesive wear is the condition of shear frictional junction where frictional transfer is observed when surface of soft (polymer) and hard body (metal) comes in a contact51. The formation of micro particle film has been observed by the virtue of such frictional transfer which results in two conditions i.e. the condition when film is carried away by hard surface (increases wear rate) or when film maintains its contact with soft body (reduced wear rate). The observation of adhesive wear and frictional transfer has been further corroborated in the evaluation of wear characteristics of printed mollusc architectures. It has been observed that the energy absorption ability of the shell matrix (especially nacre) dramatically reduces under the condition nanoshock generated during the dry friction test due to the formation of nano-debris as a result of crack migration to the tablets52. Wear rate is further augmented by the thermal induced wear damage which results in organic layer degradation52. Since, the current study does not involve the incorporation of organic biopolymer therefore, the adhesive wear could be the function of surface roughness, origin of interfacial interaction of the layers, transfer of sliding heat and the formation transfer film. It is evident from the table 6 that the performance of (wear rate) various microstructural architecture is dramatically influenced by the orientation and manipulation of exoskeleton design. Therefore, the complex tablet orientation in crossed lamellar structure is envisioned to impart the preeminent effect on energy dissipation during the frictional conditions. The effect



of structural orientation on frictional attribute of a surface can be supported by the report of Harrison et al. They have demonstrated that self-assembled n alkane chains provided low coefficient of friction when sliding in the chain direction while sliding opposite to the chain direction contemplated higher coefficient of friction53. In addition, Jang et al have elucidated that if the direction of orientation is in sliding pathway the coefficient of friction will be low due to the low barrier to the interfacial slip while in opposite direction reorientation and scission are encountered54. The higher coefficient of friction for cross lamellar structure can be also attributed to the stacking of ABS tablets at 45⁰ which apprehend anisotropic effect on its surface when exposed to the wear condition during the friction test. Since, nacreous structure was built by pilling of parallel individual ABS tablet therefore, the interfacial slip dominates the frictional characteristics of the developed architecture.

Fig 8. Pin on Disc Arrangement for Friction Test Table 6. Illustration of Friction behavior of Mollusc architectures Design

Pristine

Coefficient of

Wear Rate

friction (ABS)

(x10-9 m3/Nm) (ABS)

0.460

0.00022


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Nacre Structure

0.47

0.00015

Foliated

0.43

0.0009

Cross Lamellar

0.50

0.00012

Complex

0.42

0.00019

Cross

Lamellar

Conclusions In this study, we have demonstrated the bionic prototyping of molluscan shells architecture including Nacre, foliated, Cross Lamellae and Complex cross lamellae via layer by layer 3D printing of engineering thermoplastic Poly (acrylonitrile-co-butadiene-costyrene) tri block Copolymer. The effect of microstructural manipulation on mechanical and frictional attributes of printed interdigitating exoskeleton molluscan structure was investigated. We envisioned that though nacre is extensively reported for its unprecedented combination of toughness and strength but under the application of sudden load in impact condition, crossed lamellar microstructure demonstrated enhanced efficacy compared to nacreous structure when biopolymers are excluded from the design strategies. In addition to the high impact characteristics, crossed lamellae have demonstrated improved wear rate compared to the other structure due to its tablet orientation against the direction of sliding condition. We believe that such microstructural dependent site-specific printing will render new avenues for the development of advanced mechanostabilized and sustainable polymer composite for engineering applications. Acknowledgements The authors acknowledge Dr. H Gokhale, Vice Chancellor, DIAT-DU and Prof Peter Hodgson, Deputy Vice-Chancellor (Research), Deakin University, Australia for their



continuous encouragement and support. Authors would also like to thank Mr. Dhanajay Gunjal for his support in FESEM. Authors would also like to thank Dr. TU Patro for his support in tensile testing of the samples. Authors are thankful to all group members and staff for their support and inputs. References 1.

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