BIKAS: Bio-Inspired Knowledge Acquisition and Simulacrum—A Knowledge Database to Support Multifunctional Design Concept Generation

ABSTRACT A detailed acquisition, analysis, and representation of biological systems exhibiting different functions is required to develop unique bio-inspired multifunctional conceptual designs and methods. This paper presents BIKAS: Bio-inspired Knowledge Acquisition and Simulacrum, a knowledge database of biological systems exhibiting various functionalities, developed based on case-based bio-inspired examples from literature. The knowledge database represents the biological features, their characteristics, and the function exhibited by the biological feature as a combination of its integrated structure and structural strategy. Furthermore, this knowledge database is utilized by the Expandable Domain Integrated Design (xDID) model that works on classifying, mapping, and representing biological features into their respective geometric designations called Domains. The combination of features from the Domains results in the generation of multifunctional conceptual designs. In addition, Meta-level design factors are proposed to aid designers in filtering the biological features and their respective functions having a similar structural strategy, thus aiding designers in rapidly selecting and emulating biological functions.


INTRODUCTION
Bioinspiration is a constant source of inspiration for many engineers, scientists, and designers to generate innovative and unique design solutions for complex engineering problems.Bio-inspired design (BID) is an

BIKAS: Bio-Inspired Knowledge Acquisition and Simulacrum-A Knowledge Database to Support Multifunctional Design Concept Generation
approach that uses analogies to biological systems to extract innovative solutions to solve difficult or complex engineering problems [1,2].Ever-increasing human demands and environmental problems require innovative solutions.For example, sustainable products are required to reduce the overall environmental impact, and innovative solutions are required to tackle emerging complex engineering problems such as water treatment, waste management, etc. Bioinspiration is a source to provide innovative solutions to such problems.However, the traditional product development processes depend on the incremental improvements of single products [3].Therefore, seeking a radical, innovative, and agile product development process is imperative to satisfy current human demands and needs.Bio-inspiration or Bio-inspired design is one of the emerging creativity and innovation methods [4] that aids in developing innovative and efficient products.Biological systems are multifunctional as they survive by simultaneously performing various tasks [5].Moreover, biological systems perform various functions by reducing the number of parts, thus reducing material and energy consumption [6][7][8].Biological systems offer highly efficient solutions for various emerging complex engineering problems, for example, effective energy absorption [9], effective antibiofouling and self-cleaning [10], heat isolation, heat exchangers, vibration control, etc [11].Nevertheless, repositories of biological features exhibiting various functions are required to develop methods and frameworks aimed at utilizing nature principles to achieve innovative conceptual designs for multifunctional bio-inspired designs.The following sub-section provides the details of the existing repositories of biological information.

Repositories for Biological Information
Biological information, representation, and analysis are essential for understanding the biological system or a feature for emulating its functionality.Repositories were developed to enhance the understanding of biological systems, biological features, and the functions exhibited by them.For example, Ideas Inspire is a software-based repository representing biological systems using the SAPPhIRE model of causality [12].DANE is another repository of biological systems represented using function-based approaches such as Structure-Behaviour-Function (S-B-F) [12].BioTRIZ is a unique approach developed to integrate biological knowledge and TRIZ problem-solving technique.The biological information is represented using a descriptive approach and interactively positioning the biological strategy in the BioTRIZ contradictory matrix [13].
AskNature is an interactive software-supported repository of biological information represented by using a functional, hierarchical taxonomy called Biomimicry Taxonomy [13,14].
Table 1 presents the existing repositories of biological information, the level of abstraction, and the approach used for the representation of the biological system.Ideas Inspire and DANE abstract the biological analogy as a whole system.Both repositories use functional modelling technique.Functional modelling is a system-level representation in the form of a block or tree diagram that describes the process flow between components, for example, matter, energy, or signal.This approach is often associated with the functional decomposition of the overall function into sub-functions [15].On the other hand, AskNature and BioTRIZ have their own unique modes of representation of biological analogies.AskNature uses Biomimicry Taxonomy and BioTRIZ uses descriptive representation integrated with parameters such as substance, structure, time, space, energy, field, and information adaptation [16].However, to reduce the complexity

BIKAS: Bio-Inspired Knowledge Acquisition and Simulacrum-A Knowledge Database to Support Multifunctional Design Concept Generation
in abstraction of a functionality in a biological organism and enhance the rapidity in ideation, a unique biological knowledge database called BIKAS is introduced.This paper presents the knowledge database BIKAS: Bio-inspired Knowledge Acquisition and Simulacrum of biological systems exhibiting various functions represented according to their biological features, characteristics, and function as a combination of integrated structure and structural strategy.BIKAS is developed by analysing over 50 case-based bio-inspired examples from the literature.This paper is organized as follows: Section 2 provides a description of the biological features, their characteristics, the integrated structure, the structural strategy, and the BIKAS.Furthermore, it presents data visualisation of the knowledge database.Section 3 presents the construction of BIKAS and criteria for evaluating databases.Section 4 elaborates the utilization of the knowledge database in the xDID model.Section 5 presents conclusions.

BIKAS
BIKAS is built based on the case-based bio-inspired design examples in the literature.The biological systems are represented according to the biological feature, its characteristics, and the function exhibited by the feature as a combination of the integrated structure and the structural strategy.Table 2 presents the abstraction level, mode of representation, and methods and model associated with the BIKAS.The biological features that exhibit various functions are mapped to their structure, and structural strategy.The level of abstraction of a biological entity in the case of BIKAS is at the biological feature level or in other words at the component level.

BIKAS: Bio-Inspired Knowledge Acquisition and Simulacrum-A Knowledge Database to Support Multifunctional Design Concept Generation
The following points describe each component of the BIKAS.
• The Meta-Level Embodiment function represents the function exhibited by the biological feature at the embodiment function level (at the physical structure level) [15,17].• The Biological features refer to the morphological and anatomical features observed in plant and animal kingdoms.• The Capitalize feature characteristic represents the feature's appearance, apparent form, or physical trait.For example, body/skin texture, hard outer composite covers like outer composite plates, outer composite tiles, outer composite shells, cellular structures, etc. • The Capitalize structure represents the physical description of a multiscale structure (e.g., Micro/ Nanostructure, Macrostructure, and the presence of wax layers on the Structure, etc.) [15].• The structural strategy represents the integrated structural configuration (e.g., arrangement of the micro/nanostructure, packing of the micro/nanostructure, orientation of micro/nanostructure, symmetry, asymmetry, or patterns of tessellations, etc.) and changes in the structural configuration due to stimulus.Stimulus are by the other interacting elements connected to the structure (e.g., erection of scales, change in skin compliance, etc.) [15].
Figure 1 shows the schematic representation of the biological feature its characteristics and the function exhibited as a combination of its integrated structure and structural strategy.The repel water function exhibited by the Butterfly wings shown in Table 3 is an example of BIKAS.The meta-level embodiment function to repel water exhibited by the butterfly wings is a combination of the integrated structure: a directional hierarchical arrangement of the nano-tips on the micro projections [18] and the structural strategy: orientation of the structure (on the wing) in the downward direction [18].Nano-tips on microstructures [18] (Arrangement and Orientation)

BIKAS: Bio-Inspired Knowledge Acquisition and Simulacrum-A Knowledge Database to Support Multifunctional Design Concept Generation
The directional hierarchical arrangement.Wings when tilted downwards.[18] Figure 2 shows the schematic sketch of the nano-tips and hierarchical microstructure of the butterfly wings.The following sub-section provides the BIKAS.In BIKAS, the key structural strategies are represented in bold italics and where are braces?BIKAS is utilized by Domain Integrated Design (DID), a newly developed bio-inspired design method for multifunctional conceptual designs.DID differs from other multifunctional bio-inspired design methods by following a unique approach of classification, mapping, and representation of biological features.The biological features responsible for exhibiting various functions are classified by their feature characteristics to their respective geometric designations called Domains.The Domains are Surfaces, Cellular Structures, Cross sections, and Shapes.Furthermore, the classified biological features are mapped to the tissues they originate from.In addition, the function exhibited by the biological features is represented as a combination of the integrated structure (often multiscale) of the biological feature and its structural strategy.A detailed comparison of the DID method and existing multifunctional bio-inspired design methods is reported in [16].Expandable Domain Integrated Design (xDID) model is an extension of the proposed DID method to facilitate the classification of complex biological features that exhibit various functions that cannot be described according to the current definitions of the DID method.Furthermore, the xDID model facilitates Data Intelligence Just Accepted MS. https://doi.org/10.1162/dint_a_00240

BIKAS: Bio-Inspired Knowledge Acquisition and Simulacrum-A Knowledge Database to Support Multifunctional Design Concept Generation
the creation of micro-Domains within the same Domain for accurate description and classification of the biological feature.The classification, mapping, and representation of the xDID model with case studies are detailed in [15].The next section presents the knowledge database that is BIKAS.The biological analogies and their information presented in BIKAS are manually curated.Currently, around 50 biological features are analysed and represented in BIKAS.The knowledge database is expected to expand as more biological entities are analysed and represented according to the mapping process in BIKAS.Furthermore, expansion of the BIKAS can be used for implementing natural language processing algorithms for an automated population of the database.

Knowledge Database (BIKAS)
Table 4 describes the meta-level embodiment functions exhibited by biological features, their characteristics, integrated structure and the structural strategy.

Data Visualisation
This section provides the visualization of BIKAS that comprises the biological features performing various functions.Figure 3 presents the biological features, their characteristics and the function exhibited by the features.This visualization provides an insight that the biological features of distant biological organisms performing a similar function.
In literature, this phenomenon is described as convergent evolution, where distant biological systems exhibit the same function in radically different ways.For example, the stem cross section of the bamboo tree exhibits the function of absorb energy [9].Likewise, the elytra of a beetle forewing exhibit similar function of absorb energy [35].Another observation from Figure 3, is that some feature exhibit more than one function for example, the reduce aerodynamic and fluidic drag function is exhibited by shark [46] and dolphin skin [47] and the resist bending and absorb energy function of the Toucan and Hornbill beaks [45].
The Figure 4 shows the measure of biological feature characteristics that were mimicked to achieve a particular function in various case-studies.As shown, the biological feature characteristics Body/Skin texture (Animals) was mimicked the most followed by the Body/Skin texture (Plants).As BIKAS expands, more features will be added and expected to provide a more comprehensive and more detailed and user interactive approach in utilizing the knowledge database.

CONSTRUCTION FLOWCHART OF BIKAS
BIKAS is a unique knowledge data that involved a manual search, acquisition, analysis, and curation.For structured knowledge bases and repositories that involve creation of representation modes for understanding biological phenomenon require human interaction, initiation and curation [13].A construction flowchart is necessary to describe the creation of BIKAS.Construction flowcharts enable to reproduce, populate, and enhance the understanding of biological feature of a biological entity.Figure 5 shows the The microstructures are often pointed in shape [10] (Arrangement)

BIKAS: Bio-Inspired Knowledge Acquisition and Simulacrum-A Knowledge Database to Support Multifunctional Design Concept Generation
The random arrangement of micro perturbances [19] Micro/Nano projections (Rose petal) Body/Skin texture (Plants) Micro bumps are often rounded or spherical in shape [20] (Packing) (Rosa CV.Showtime) is the species that showed low adhesion because of the densely packed micro bumps [20] Micro/Nano projections (Butterfly Wings) Body/Skin texture (Animals) Nano-tips on microstructures [18] (Arrangement & Orientation) The directional hierarchical arrangement.
Wings are tilted downwards [18] Micro/Nano projections The hexagonal arrangement of spherical capped protuberances and the insect always stays in an upright position [23] Hair (Water Strider) Body coat (Animals) Each leg is covered by an array of inclined, tapered hairs of conical shape, where each hair further has longitudinal and quasi-helicoidal nano grooves which enhance the water repulsion [24] (Orientation & Arrangement) Inclined and tapered hair [24]; and Titled and randomly arranged micro-hair [25]; (Arrangement) A compact hexagonal non-close packed (hcp) arrangement with triangular voids of less than 3 micrometres.Tight packing of protrusions [19] Adhere to Surface Hair (Gecko Feet) Body coats (Animals) Nanofiber hair (Setae), Hierarchical arrangement of lamellae, setae stalks, and spatula tips [28] (Packing & Orientation) Close packed and branched setae [29]; and Sticks when pulled from the palm towards the tip of the toe [28]; Adhere to an inclined surface Micro/Nano projections (Rose petals) Body/Skin texture (Plants) Round and grooved fine structure on the plump.Micron scale nubs (epidermis) of the rose petal surface [30] (Orientation) The geometry of submicron scale cuticular folding forms.The round and grooved fine Structure is oriented downwards from the nubs of the petal surface [30]; Micro/Nano projections (Butterfly wings) Body/Skin texture (Animals) Flexible nano-tips on ridging nano-stripes and micro-scales [18] (Arrangement & Orientation) Direction-dependent arrangement when wings are tilted upwards [18]; The direction of the corrugation is parallel to the direction in which a pangolin dig [31] Resistance to biofouling Placoid Scales (Sharkskin) Scales (Animals) The microstructure of sharkskin has a V-shaped micro-trench structure [33] (Packing & Arrangement) Overlapping and dense stacking of scales [33]; Different shark species have a slightly different microstructure.Body/Skin texture (Animals) Grooves, and micro bumps on the surface can improve the antierosion performance [34] (Arrangement) The Random arrangement of the micro bumps [34] Resist Shear Tiles (Ray Fish) Hard outer cover Tiles (Animals) Surface tiles [11] (Arrangement) The periodic arrangement of surface tiles [11] Resist compression Outer plate (Mantis shrimp dactyl club) Hard outer cover Plates (Animals) Uniaxial chitin proteins and nanofibers fibres stacked along a helical twist in a periodic region [35].

(Arrangement)
Arrangement of nanofibers stacked along a helical twist in periodic region in between the impact region and trained region [35].
Outer shell (Abalone) Hard outer cover Shell (Animals) Surface tiles with an outer prismatic layer and inner nacreous layer [36] (Arrangement) The periodic arrangement of stacked Voronoi palates in a brick-mortar arrangement with an organic matrix in between [36] Resist Arrangement of dense vascular bundles surrounded by porous nested structure [41]; Stochastic-Voronoi [42] Resist bending Leaves-cross section (cattail) Cross-section of the body part (leaves) Gradual varying I-beam sections with high-density foam at the bottom [43] and [44] (Symmetry) Symmetry of the I-beam cross section along the axis (Skin stimulus) Shark scales are flexible and might erect passively [46] Sharkskin scales are made of enamels, combined with sharp spines and a rectangular base plate which goes deep inside the skin.The combination of the base plate and the spine forms a firm cantilever beam structure [46] (Orientation) The direction of the scales is parallel to the swimming direction [46] The size and shape of the scales vary at different parts of the body, i.e., from head to tail [46] Micro/Nano projections (Dolphin) Body/Skin texture (Animals) Presence of micro-rigids on the skin [47] (Skin stimulus) Dolphins can control their muscle to change their skin compliance [47]

(Orientation)
It becomes extremely slippery when it becomes wet.The direction of the epidermis microstructure (cresent shaped) is directed inwards [51] Reduce rupture or puncture

Reduce weight and Resist compression
Cuttle Bone (Cuttlefish) Periodic tessellation (Animals) Wall-septa arrangement with high porosity [54] (Periodic Tessellations) Wall-septa hierarchical arrangement [54]; Periodic-Wall septa [55] Reduce drag Overall shape (Penguin) Full body contour (Animals) Spindle shape and formation of microbubbles due to feathers on the surface [47] (Symmetry) Symmetry of the body contour along the axis.
Overall shape (Boxfish) Full body contour (Animals) Symmetrical box-shaped Structure [56] and [57] (Symmetry) Symmetry of the body contour along the axis.between lower and upper skin (Honeycomb cells) [35] (Hierarchical Tessellations) Trabeculae at the intersection of honeycombs on lower and upper skin and chitin fibres on trabeculae arranged in linear or spiral manner [35] Overall shape (Diatom) Full body contour (Animals) The transverse corrugated structure along the body [60] (Symmetry) Symmetry of the body contour along the axis.

Stem-cross section (Bamboo)
Cross-section of the body part (Stochastic tessellation of gradient pores: Vascular bundles) Vascular bundle that contains a multi-cell structure with gradient distribution [9] (Symmetry) Symmetry of vascular structural cross section along the axis.All the three phases involved in a manual search, acquisition, analysis, and curation.The acquired data is stored as open-source database using an interactive web-based data visualisation tool.The data sources for data acquisition are mainly research articles and case-studies of biologically inspired structures searched in popular sources such as Scopus, Google scholar, and special issues and journals in bio-inspired design.Often biological-inspired case studies may not have all the necessary information for the construction of BIKAS.For example, a detailed description of the structure and the structural strategies (configuration of the structure).In such cases, more articles regarding the biological system are researched and analysed for the construction.

Evaluation Criteria for BIKAS
The effectiveness of qualitative databases that involves in analogical transfer such as biological data for engineering design depends upon how well the biological data is understood [70].For bio-inspired design knowledge databases that only has mode of representation of biological features, the evaluation is based on how well the biological information is abstracted and understood, and how well the information is used to build a solution.Two such modes of biological representation have been evaluated so far.Those are namely, SAPPhIRE [70] and S-B-F (Structure-Behaviour-Function) [71].The evaluation is a comparative study on SAPPhIRE representation of biological information and a generic text-image representation through a series of questionnaires provided to the designers [70].Similarly, a comparative study between S-B-F representation, text-only and text-graphic-tabular representation was carried out through a series of questionnaires [71].Table 5 presents the evaluation criteria for evaluating repositories for bio-inspired design.As shown, these modes of representations do not have a method associated with them.Such repositories without an associated methods are evaluated through a comparative study.Table 5. Evaluation criteria for repositories for bio-inspiration.

Mode of representation (biological information)
Associated method Approach Procedure

SAPPhIRE Not Applicable Comparison between modes of representation Questionnaire S-B-F Not applicable
Comparison between modes of representation Questionnaire However, BIKAS is a unique database of biological information represented as a mapping between function-feature-structure-structural strategy.In addition, a method classifying the biological features according to their characteristics into their geometric designations called Domains is associated with the database.The principle is combination of features from different Domains results in multifunctional conceptual designs.BIKAS and DID are unique mapping and classification of biological features.The evaluation criteria for such a representation and its associated classification method are the design and simulation-based evaluation of early-stage embodiment designs.

BIKAS: Bio-Inspired Knowledge Acquisition and Simulacrum-A Knowledge Database to Support Multifunctional Design Concept Generation
The effectiveness of such a complex mapping and classification of biological features is verified by designing unique bio-inspired multifunctional early-stage embodiment product concepts and validating them using computer simulations.Several case-studies were published that evaluates the effectiveness of the knowledge database and the method.For example, multifunctional bio-inspired painless sutures [53], multifunctional bio-inspired effective heat transfer and low pressure drop structures for aerospace applications [72], multifunctional bio-inspired non-pneumatic tire design for effective friction management and impact resistance [73].

CASE STUDY OF BIKAS TO SUPPORT MULTIFUNCTIONAL BIO-INSPIRED DESIGN GENERATION MODEL
xDID model works on classifying the biological features into their geometric designations, mapping the classified biological features to their respective tissues from which they originate, and representing the function performed by the biological features as a combination of the integrated structure and its structural strategy.In this model, firstly, the biological features are classified by their feature characteristics to their respective geometric designations called Domains.The Domains are namely Surfaces, Cellular structures, Cross-sections, and Shapes.Domains represent different biological features performing various functions, mapped to their tissues with a common geometric designation.Figure 6 shows the representation of the repel water function exhibited by the biological feature, which is the micro/nano projections of rose petals as a combination of its integrated structure and structural strategy.The integrated Structure is the rounded micro-bumps, and its structural strategy is the microstructure's random arrangement and dense packing.In addition, the biological feature is mapped to the biological tissue from which it originates.Data Intelligence Just Accepted MS. https://doi.org/10.1162/dint_a_00240

Domain Definitions
The descriptions of the classified Domains was extensively discussed in [15].However, this sub-section provides a brief description of the Domains.The Surfaces Domain comprises the biological features that can be described with feature characteristics such as animal and plant body/skin textures, structures that form the body coat, for example, wool, hair, etc., and the elements that include the hard outer and sandwiched cover such as shells, plates, and tiles.The Cellular structures Domain comprises the biological features described as porous prismatic and foam structures arranged in various tessellated patterns, namely periodic, stochastic, and hierarchical, with feature characteristics such as periodic tessellations with unary, binary, ternary or quaternary connections, stochastic tessellations with Poisson distribution, Voronoi or crystal growth patterns, and finally hierarchical tessellation with branching, nested or overlaid connections [11].The Cross-sections Domain comprises the biological features with the characteristic of a cross-section of the body or a part of the body.Cross-sections are described as shapes obtained by cutting a body along the lateral and longitudinal axis.The shape Domain comprises the biological features with characteristics of the body's external form or contour, such as a boxfish shape [56] for drag reduction or a part of the body's external form or contour that exhibits a specific functionality.

BIKAS: Bio-Inspired Knowledge Acquisition and Simulacrum-A Knowledge Database to Support Multifunctional Design Concept Generation
However, biological features are highly complex structures.They cannot be described by just one characteristic, making it highly impossible to systematically classify biological features into a finite number of Domains.xDID facilities addition of new Domains for the features that cannot be described according to the definitions of the current study.In addition, xDID offers the creation of micro-Domains for more precise description and classification of the biological feature by its feature characteristics.As shown in Figure 9 [15], the Surfaces Domain can be sub-divided into micro-Domain that comprises of biological features with feature characteristic of hard outer cover such as sandwiched plates, tiles, and shells.Similarly, the cellular structures Domain can be subdivided into micro-Domains by the type of connections such as beam based connections or face based connections [15].

Meta-level Design Factors
In xDID, the functionality is seen as a combination of the integrated structure and the structural strategy.The proposed Meta-level design factors are the Domain-specific structural strategies observed from the literature case studies that influence a biological system's functions.The abstracted Meta-level design factors aid as a filter to extract the features and their functions from BIKAS that are influenced by a similar biological structural strategy.
Table 7 presents the list of Meta-level design factors for various Domains and sub-Domains proposed in xDID based on the analysis of bio-inspired design cases.The Meta-level design factors are filters to extract features and functions within the same Domain that share a similar structural strategy.This extraction aid designers providing with different biological features and their functions that have a similar strategy thus enhancing the rapid selection and emulation of the biological features for rapid ideation process.Figure 10 shows the application of Meta-level design factor as a filter on the knowledge database to extract biological features that exhibits a particular function with a similar structural strategy.Table 8 shows an example of the application of the Meta-level design factors, where two functions one is repel water function by lotus leaf and the other is resist erosion function by scorpion skin, both having the similar structural strategy that is random arrangement of the micro/nano projections.

CONCLUSIONS
To develop multifunctional bio-inspired conceptual designs and methods a detailed acquisition, analysis and representation of the biological features are required.BIKAS is a knowledge database developed based on the case-based bio-inspired design examples from the literature.BIKAS aids in developing multifunctional bio-inspired design concepts and methods.xDID model is one such method developed utilizing the knowledge base.The unique classification, mapping, and representation of biological features will bridge Micro-structures, grooves, and bumps on the surface can improve the anti-erosion performance [34].

(Arrangement)
The Random arrangement of the micro bumps [34] the gap between biology and engineering fields and enhance biologists' collaboration that results in agile innovation.Unlike the existing multifunctional design methods, the xDID method enhances the rapid ideation process.However, the current approach has certain limitations.Initial DID method emphasised on assigning the biological features to four Domains namely Surfaces, Cellular Structures, Cross-sections, and Shapes.But in the vast Plant and Animal kingdoms complex functional biological features exists that cannot be assigned to a Domain based on the current definitions.To tackle such a complex situation xDID approach is introduced that facilitates the creation of micro-Domains within a Domain and new Domains.
BIKAS is a unique mapping of function-feature-structure-structural strategy in association with DID method that classifies features into their geometric designations called Domains results in generation of multifunctional bio-inspired conceptual and early-stage embodiment designs.Moreover, the abstraction of biological entities is at its feature level or component level.This enhances the rapidity in ideation by replicating similar structures.However, BIKAS lacks in a systemic-level analysis of a biological entity.Nevertheless, BIKAS can be integrated with other system-level approaches for representation to enhance the understanding of the biological entity both at system and component levels.This paper presented a knowledge database of different biological features performing various functions.Furthermore, functions exhibited by the biological features are represented as a combination of integrated structure and the structural strategy.Additionally, xDID model for generation of multifunctional conceptual design is discussed.Finally, Meta-level design factors are abstracted, which are the Domain-specific factors that act as a filter to extract the biological features and their functions within the same Domain that have a similar structural strategy.Meta-level design factors aid designers in filtering and sorting the biological features that have a similar structural strategy for rapid selection and emulation.Effective utilization the BIKAS and xDID model is achieved by populating the existing knowledge database and addition of new Domains.The next step is to develop an open-source tool for designers, biologists, and scientists to utilize the xDID model.

Figure 1 .
Figure 1.Representation of the Biological Systems with biological features performing a function as a combination of its integrated structure and the structural strategy.

Figure 2 .
Figure 2. Conceptual sketch of the integrated structure of the butterfly wings for repel water functionality.
texture (Animals) Overlapping Triangular scales [31] (Packing & Arrangement) Outward projection of Pangolin scales for defence & Overlapping scales [31- where the inner core is made up of trabeculae foam[44] structure with coneshaped columns and nodes.The individual cell takes the shape of a tetragon or pentagon[9] Conical Corrugated structure[9] (Symmetry) Symmetry of the conical corrugations and the cross section along the axis

Figure 3 .
Figure 3. Visualisation of the biological feature, the function the feature exhibits, and the biological feature characteristic.

Figure 6 .
Figure 6.Representation of the Domain, Function, and Tissue of the biological feature of a Rose petals.

Figure 7
Figure 7 shows the classification of biological features to their respective geometric designations (Domains) based on their biological feature characteristics for the xDID model.The shapes and crosssections are considered sub-Domains of surfaces and cellular structures because the function exhibited by biological features in these Domains are due to the combination of different biological characteristics or different biological tissues.The cross-sections and shapes sub-Domain have an associated biological feature characteristic belonging to Surfaces Domain or Cellular structures Domain.Figure 8 shows the comprehensive visual representing the biological feature, the function the biological feature exhibits, and the Domain to which the feature is assigned.

Figure 8 .
Figure 8. Visualisation of the biological feature, the function the feature exhibits, and the Domain the feature belongs.

Figure 9 .
Figure 9. Micro-Domains representing more accurate description and classification of biological features [15].

Figure 10 .
Figure 10.Application of Meta-level design factors for extraction of biological features and their functions with similar structural strategy.

Table 1 .
Existing repositories for biological information.

Table 3 .
Meta-level embodiment function, biological feature, biological feature characteristic, integrated structure, and the structural strategy of the butterfly wings.

Table 4 .
Biological features, their characteristics, integrated structure, and structural strategy.

Table 7 .
Application of Meta-level design factors.