Academic literature on the topic 'Biomimetic surface design'

Since the invention of the aircraft, there has been a need for better surface design to enhance performance. This thirst has driven many aerodynamicists to develop various types of aerofoils. Most researchers have strongly assumed that smooth surfaces would be more suitable for air transport vehicles. This ideology was shattered into pieces when biomimetics was introduced. Biomimetics emphasized the roughness of a surface instead of smoothness in a fluid flow regime. In this research, the most popular 0012 aerofoils of the National Advisory Committee for Aeronautics (NACA) are considered to improve them, with the help of a surface pattern derived from the biological environment. Original and biomimetic aerofoils were designed in three dimensions with the help of Solidworks software and analyzed in the computational flow domain using the commercial code ANSYS Fluent. The implemented biomimetic rough surface pattern upgraded the NACA 0012 aerofoil design in the transonic flow regime. Lift and viscous forces of the aerofoil improved up to 5.41% and 9.98%, respectively. This research has proved that a surface with a little roughness is better than a smooth surface.

Through billions of years of evolution, a latent record of successful and failed design practices has developed in nature. The endeavors to exploit this record have resulted in numerous successful products in various fields of engineering, including, but not limited to, networking, propulsion, surface engineering, and robotics. In this work, a study of existing biomimetic designs has been carried out by categorizing the designs according to the biological organizational level, the abstraction level, and a novelty measure. The criterion of novelty has been used as a partial measure of the quality of bio-inspired and biomimetic designs already introduced, or ready to be introduced to the market. Through this review and categorization, we recognize patterns in existing biomimetic and bio-inspired products by analyzing their cross-categorical distribution. Using the distribution, we identify the categories which yield novel bio-inspired designs. We also examine the distribution to identify less explored areas of bio-inspired design. Additionally, this study is a step forward in aiding the practitioners of biomimetics in identifying the categories which yield the highest novelty products in their area of interest.

A global interest was awarded to study the natural superhydrophobic surfaces since the description of the Lotus Effect by Barthlott and Neinhuis in 1997. Natural biomimetic surface merits of micro/nano-roughness, water contact ˃ 150°, sliding angles ˂10°, and minimized free-energy characteristics would motivate the dynamic fabrication of superhydrophobic surfaces. This critical review introduces an architectural panorama of numerous structural designs of natural superhydrophobic surfaces. Also, it discussed the fundamentals of self-cleaning and wetting theories to develop superhydrophobic structures. This progress review concentrates on superhydrophobic materials' applications for self-cleaning marine antifouling surfaces. It introduced an in-depth understanding of the structural design-superhydrophobic property relationship of the natural nano-wettable surfaces. It is technically first to shed light on the inner basics and platform for surface non-wettability and facilitates the way for design biomimetic self-cleaning antifouling surfaces.

Sand erosion is a phenomenon that solid particles impinging to a wall cause serious mechanical damages to its surface. It's tough to be a machine in the desert: particles of dirt and sand work their way into moving parts, where they abrade helicopter propellers, airplane rotor blades, pipes and other equipments. However, the desert scorpion (Androctonus australis) live their entire lives subjected to blowing sand, yet they never appear to be eroded. In this study, the anti–erosion characteristic rules of the scorpion surfaces under aerodynamics effect of gas/solid mixed media were studied. Biomimetic linear–cutted surfaces consisting of an array of three types of grooves, square–type, V–type and U–type, were designed and investigated to quantify their erosion wear resistance properties. A smooth surface sample was fabricated for comparison. The ANSYS-Fluent simulation of biomimetic models showed that the V-type groove sample, inspired by the desert organism's surface with different morphologies, exhibited the best erosion resistance. It also indicated the anti-erosion property of biomimetic samples could be attributed to the rotating flow in the grooves that reduces the impact speed of particles. The synchronized erosion test confirmed the conclusions. Furthermore, an application exploring of bionic blades on a centrifugal fan was conducted. The blades with optimum parameters could effectively improve anti-erosion property by 29%. We envision that more opportunities for biomimetic application in improving the anti–erosion performance of parts that work under dirt and sand particle environment will be proposed.

Abstract Biofouling is an unwelcomed phenomenon where unwanted biological matter adheres to surfaces with the presence of water, resulting in alteration to the properties of the surface. This affects many industries, especially the marine industry. Multiple biofouling control studies have been conducted to minimize damage and maintenance cost of these surfaces. With rising concerns on the toxicity of current control methods towards the environment, non-toxic methods shown to be effective are surface modifications such as self-cleaning or biomimetic textured surfaces. One of the biomimetic surfaces, shark’s skin has shown anti-fouling properties due to its surface riblets with low drag properties based on studies done. However, few researches are conducted to implement these biomimetic surface topographies for real anti-fouling applications. Therefore, this project explores the possibilities in implementing biomimetic surface topographies such as shark’s skin in real life applications using computational fluid dynamics (CFD) analysis and also to manufacture these surfaces using 3D printing methods. A computer-aided design (CAD) model of shark skin and un-patterned surface topographies are used to study the behavior of fluid over these surfaces in CFD fluent in ANSYS software. The hydrodynamic variable data such as wall shear stress over the surface topography is represented in a contour and vector plot, these results are then analyzed. According to the hypotheses, the biomimetic shark skin surface topography will show higher wall shear stress, indicating anti-fouling properties. In the next part of this project is the manufacturing of these surface, the goal is to provide a cheaper alternative to current micro-structured surface production methods such as photolithography. Additive manufacturing such as fused deposition modeling (FDM) 3D printing can potentially provide a manufacturing method with a much lower cost and time needed. Thus, 3D printing of the biomimetic shark skin surface topography will be carried out in this project to determine if FDM can provide a manufacturing solution to anti-fouling micro-topography surfaces.

This paper explores the contact behaviour of simple fibrillar interfaces designed to mimic natural contact surfaces in lizards and insects. A simple model of bending and buckling of fibrils shows that such a structure can enhance compliance considerably. Contact experiments on poly(dimethylsiloxane) (PDMS) fibrils confirm the model predictions. Although buckling increases compliance, it also reduces adhesion by breaking contact between fibril ends and the substrate. Also, while slender fibrils are preferred from the viewpoint of enhanced compliance, their lateral collapse under the action of surface forces limits the aspect ratio achievable. We have developed a quantitative model to understand this phenomenon, which is shown to be in good agreement with experiments.

Surgical site infection is a common cause of post-operative morbidity, often leading to implant loosening, ultimately requiring revision surgery, increased costs and worse surgical outcomes. Since implant failure starts at the implant surface, creating and controlling the bio-material interface will play a critical role in reducing infection while improving host cell-to-implant interaction. Here, we engineered a biomimetic interface based upon a chimeric peptide that incorporates a titanium binding peptide (TiBP) with an antimicrobial peptide (AMP) into a single molecule to direct binding to the implant surface and deliver an antimicrobial activity against S. mutans and S. epidermidis, two bacteria which are linked with clinical implant infections. To optimize antimicrobial activity, we investigated the design of the spacer domain separating the two functional domains of the chimeric peptide. Lengthening and changing the amino acid composition of the spacer resulted in an improvement of minimum inhibitory concentration by a three-fold against S. mutans. Surfaces coated with the chimeric peptide reduced dramatically the number of bacteria, with up to a nine-fold reduction for S. mutans and a 48-fold reduction for S. epidermidis. Ab initio predictions of antimicrobial activity based on structural features were confirmed. Host cell attachment and viability at the biomimetic interface were also improved compared to the untreated implant surface. Biomimetic interfaces formed with this chimeric peptide offer interminable potential by coupling antimicrobial and improved host cell responses to implantable titanium materials, and this peptide based approach can be extended to various biomaterials surfaces.

Lotus-effect-based superhydrophobicity is one of the most celebrated applications of biomimetics in materials science. Due to a combination of controlled surface roughness (surface patterns) and low-surface energy coatings, superhydrophobic surfaces repel water and, to some extent, other liquids. However, many applications require surfaces which are water-repellent but provide high friction. An example would be highway or runway pavements, which should support high wheel–pavement traction. Despite a common perception that making a surface non-wet also makes it slippery, the correlation between non-wetting and low friction is not always direct. This is because friction and wetting involve many mechanisms and because adhesion cannot be characterized by a single factor. We review relevant adhesion mechanisms and parameters (the interfacial energy, contact angle, contact angle hysteresis, and specific fracture energy) and discuss the complex interrelation between friction and wetting, which is crucial for the design of biomimetic functional surfaces.

Abstract. The paper presents the idea of coupled multiphysics computations. It shows the concept and presents some preliminary results of static coupling of structural and fluid flow codes as well as biomimetic structural optimization. The model for the biomimetic optimization procedure was the biological phenomenon of trabecular bone functional adaptation. Thus, the presented structural bio-inspired optimization system is based on the principle of constant strain energy density on the surface of the structure. When the aeroelastic reactions are considered, such approach allows fulfilling the mechanical theorem for the stiffest design, comprising the optimizations of size, shape and topology of the internal structure of the wing.

Application of biomimetics has expanded progressively to other fields in recent years, including urban and architectural design, scaling up from materials to a larger scale. Besides its contribution to design and functionality through a long evolutionary process, the philosophy of biomimetics contributes to a sustainable society at the conceptual level. The aim of this review is to shed light on trends in the application of biomimetics to architectural and urban design, in order to identify potential issues and successes resulting from implementation. In the application of biomimetics to architectural design, parts of individual “organisms”, including their form and surface structure, are frequently mimicked, whereas in urban design, on a larger scale, biomimetics is applied to mimic whole ecosystems. The overall trends of the reviewed research indicate future research necessity in the field of on biomimetic application in architectural and urban design, including Biophilia and Material. As for the scale of the applications, the urban-scale research is limited and it is a promising research which can facilitate the social implementation of biomimetics. As for facilitating methods of applications, it is instrumental to utilize different types of knowledge, such as traditional knowledge, and providing scientific clarification of functions and systems based on reviews. Thus, interdisciplinary research is required additionally to reach such goals.

Breast implant capsular contracture (CC) formation is a significant clinical complication post augmentation/reconstruction, which often necessitates re-operation. CC, which occurs in over half of patients post augmentation, is the formation of a fibrous internal capsule which constricts around the prosthesis leading to firmness, deformity and pain. The pathoetiology of CC is poorly understood with minimal understanding of the triggers, signalling pathways or dysregulated genes implicated in its formation. Therefore, the first aim of the present thesis was to investigate biomarkers implicated in CC formation, through whole genome microarray, quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) and immunohistochemistry (IHC) on capsule samples ranging from normal capsules (Baker Grade 1) to severely contracted capsules (Baker Grade 4). After targeted enrichment analysis, microarray identified 6 genes which were significantly dysregulated in contracted capsules. After further genomic and proteomic validation, two potential diagnostic, prognostic or therapeutic biomarkers for CC, interleukin 8 (IL8) and tissue inhibitor of metalloproteinase 4 (TIMP 4), were identified as being significantly dysregulated in CC. However, the role of each of the multiple cell types which populate a contracted capsule has yet to be determined. Therefore, the role of capsular fibroblasts was investigated using immunocytochemistry, qRT-PCR, cytokine arrays and a fibroblast populated 3D collagen matrix. IL8 and TIMP were investigated, in addition to other pro-fibrotic and pro-inflammation related candidates, to identify the role of breast capsule fibroblasts in CC formation. Normal breast fibroblast populated collagen matrices were significantly more contracted after supplementation with contracted-capsule fibroblast conditioned media, in comparison to normal growth media. It was discovered that breast-derived fibroblasts were potentially instigating and/or perpetuating CC through the transformation of normal breast fibroblasts into contracted capsule fibroblast like cells, via a paracrine signalling mechanism. The results of this work on capsular fibroblasts, and the previous work on capsular tissue, increased our understanding of the cell types and signalling molecules which are dysregulated leading to CC formation. Therefore, a novel silicone implant surface potentially capable of averting CC formation could be fabricated. Acellular dermal matrix (ADM) has been used as an adjunct in breast implant augmentation/reconstruction resulting in reduced rates of CC formation. Therefore, the micro and nanoscale topography of ADM was reproduced in a silicone surface, through a novel fabrication technique utilising comprehensive characterisation of ADM with atomic force microscopy (AFM), maskless grayscale photolithography, modified deep reactive ion etching (DRIE) and replica moulding. The features of ADM were successfully re-created in silicone to within 5 nm (Sa) and 655 nm (Sz), at a length scale of 90x90 µm2. Biological evaluation revealed that ADM PDMS surfaces promoted cell adhesion, proliferation and survival when compared to commercially available implant surfaces while cell adhesion regulating genes were upregulated and pro-inflammatory/pro-fibrotic related genes were downregulated. A reduced inflammatory cytokine response was also observed. This study demonstrates that biomimetic prosthetic implant surfaces might significantly attenuate the acute in vitro foreign body reaction to silicone. In conclusion, the results of the present thesis have enhanced our knowledge and understanding of the pathological cellular and molecular mechanisms leading to CC, in addition to the design and development of a novel, biomimetic implant surface that is potentially capable of averting the identified pathological processes in vivo.

La biomimètica o biomimetisme són termes que simbolitzen el concepte “aprendre de la naturalesa”, és a dir, aprendre dels seus sistemes, processos i models, a fi d’utilitzar la natura com a font d’inspiració per solucionar problemes de l’home. El biomimetisme és actualment un concepte recurrent en l’àrea d’enginyeria de teixits i d’ell en sorgeixen idees per obtenir plataformes més elegants i sofisticades que puguin imitar millor les interacciones entre les cèl•lules i el seu ambient. Aquesta tesi pretén desenvolupar models, en dues i en tres dimensions, mitjançant la recreació d’un o més factors característics de l’ambient natural de la cèl•lula i que juguen un paper important en el comportament cel•lular. Se sap que tant les propietats químiques com les mecàniques de la matriu extracel•lular influeixen sobre les funcions cel•lulars. És per això que es va dissenyar un nou film polimèric que pogués combinar un hidrogel, amb propietats mecàniques variables, amb un monòmer reactiu capaç d’immobilitzar biomolècules. Degut a la complexitat del polímer dissenyat, va ser necessari recórrer a una tècnica de polimerització superficial molt versàtil com és la deposició química iniciada en fase vapor (més coneguda pel seu acrònim en anglès iCVD). Els polímers varen ser àmpliament caracteritzats i es va corroborar que podien ser modificats amb petites biomolècules com ara pèptids senyalitzadors. Les superfícies resultants són bioactives i permeten l’adhesió de cèl•lules endotelials. Unes altres superfícies biomimètiques, rellevants en l’àmbit de l’enginyeria de teixits d’os, es varen obtenir a partir d’una hidroxiapatita sintetitzada pel mètode de sol-gel submergint-la en diferents medis fisiològics. La dissolució i posterior reprecipitació dels ions proporcionen una capa d’apatita amb una composició similar a la que es troba in vivo. Els experiments evidencien la importància de partir d’un material relativament soluble. És per això que la hidroxiapatita pura no és capaç d’induir la precipitació d’aquesta apatita biomimètica in vitro. Diversos investigadors han relacionat la capacitat de formar apatita amb la bioactivitat del material, entenent bioactivitat com l’habilitat d’aquests materials de promoure la unió amb l’os. Per a l’enginyeria de teixits, però, és necessari un ambient tridimensional per tal de generar un teixit artificial. S’ha desenvolupat un nou model basat en l’ús d’un gel molt tou per tal d’obtenir un teixit dur com el de l’os. Malgrat que aquests dos conceptes poden semblar contradictoris, les cèl•lules adquireixen l’habilitat d’allargar-se ràpidament i crear una densa xarxa cel•lular dins d’aquest ambient poc restrictiu des d’un punt de vista mecànic. La consegüent contracció del sistema acaba formant un constructe més petit i resistent. Aquest és un sistema biomimètic ja que promou una gran interacció cel•lular i també la condensació de les cèl•lules, esdeveniments que tenen lloc també durant el desenvolupament de l’os i el cartílag. El model es va caracteritzar extensament amb cèl•lules ostoprogenitores MC3T3-E1 que es diferenciaren amb inducció química. A més a més, es va demostrar que l’ambient tridimensional podia promoure l’expressió espontània de marcadors osteogènics. Degut a les interessants propietats del sistema, el mateix model es va utilitzar per induir la diferenciació condrogènica de fibroblastos dermals humans. Aquests tipus cel•lular no ha estat gaire explorat en l’àmbit de l’enginyeria de teixits, malgrat que ofereix un gran potencial en teràpia regenerativa. Aquest treball proporciona proves de la capacitat condrogènica d’aquestes cèl•lules en el sistema tridimensional prèviament desenvolupat.
La biomimètica o biomimetismo son términos que simbolizan el concepto “aprender de la naturaleza”, es decir, aprender de sus sistemas, procesos y modelos, y utilizarlos como fuente de inspiración para solucionar problemas del hombre. El biomimetismo es actualmente un concepto recurrente en el área de ingeniería de tejidos y de este surgen ideas para obtener plataformas más elegantes y sofisticadas que puedan mimetizar mejor las interacciones entre las células y su ambiente. La presente tesis se centra en desarrollar modelos, tanto en dos como en tres dimensiones, mediante la recreación de uno o más factores que caracterizan el ambiente natural de la célula y que tienen su rol importante en el comportamiento celular. Se conoce que tanto las propiedades químicas como mecánicas de la matriz extracelular influyen en las funciones celulares. Debido a esto, se diseñó un nuevo film polimérico que pudiera combinar un hidrogel, con propiedades mecánicas variables, con un monómero reactivo, capaz de inmovilizar biomoléculas. Debido a la complejidad del polímero diseñado, fue necesario recurrir a una técnica de polimerización superficial muy versátil como es la deposición química iniciada en fase vapor (más conocida por su acrónimo en inglés iCVD). Los polímeros fueron ampliamente caracterizados y se corroboró que podían ser modificados con pequeñas biomoléculas como péptidos señalizadores. Las superficies resultantes son bioactivas y permiten la adhesión de células endoteliales. Se obtuvieron otro tipo de superficies biomiméticas relevantes en el ámbito de la ingeniería de tejidos de hueso, a partir de una hidroxiapatita sintetizada por el método sol-gel sumergiéndolas en diferentes medios fisiológicos. La disolución y posterior reprecipitación de los iones proporcionan una capa de apatita con una composición similar a la que se encuentra in vivo. Los experimentos evidencian la importancia de partir de un material relativamente soluble. Precisamente debido a esto la hidroxiapatita pura no es capaz de inducir la precipitación de esta apatita biomimética in vitro. Varios investigadores han relacionado la capacidad de formar apatita con la bioactividad del material, entendiendo bioactividad como la habilidad de estos materiales de promover la unión con el hueso. De todos modos, en ingeniería de tejidos, es necesario un ambiente tridimensional para generar un tejido artificial. Se ha desarrollado un nuevo modelo basado en el uso de un gel blando para obtener tejido duro como el del hueso. Aunque estos conceptos pueden parecer contradictorios, las células adquieren la habilidad de estirarse rápidamente y de formar una densa red celular dentro de este gel tan poco restrictivo desde un punto de vista mecánico. La consiguiente contracción del sistema acaba formando un constructo mucho más pequeño y resistente. Este es un sistema biomimético ya que promueve una gran interacción celular y también la condensación de las células, eventos que también ocurren durante el desarrollo de hueso y cartílago. El modelo se caracterizó extensamente con células osteoprogenitoras MC3T3-E1 que se diferenciaron bajo inducción química. Además, se demostró que el microambiente tridimensional podía promover la expresión espontánea de marcadores osteogénicos. Debido a las interesantes propiedades del sistema, el mismo modelo se usó para inducir la diferenciación condrogénica de fibroblastos dermales humanos. Este tipo celular no ha sido demasiado explorado en ingeniería de tejidos, a pesar de que puede tener un gran potencial en terapia regenerativa. Este trabajo proporciona pruebas de la capacidad condrogénica de estas células en el sistema tridimensional previamente desarrollado.
Biomimetics or biomimicry are terms that imply “learning from nature”, from its systems, processes and models, in order to use nature as inspiration to solve human problems. In tissue engineering, biomimetics is nowadays a recurrent term and a source of ideas to obtain more elegant and sophisticated platforms that could better mimic the interactions between cells and their environment. This thesis is focused on developing models both in two- and three-dimensions by recreation of one or more factors of the cell natural environment that are known to play an important role in cell behavior. Since both the chemical and mechanical properties of the extracellular matrix are known to effectively influence cell function, an innovative polymeric thin film was designed combining a hydrogel with tunable mechanical properties and a reactive molecule, capable to immobilize biomolecules. Due to the complexity of the polymers, a versatile technique such as initiated chemical vapor deposition (iCVD) was required for the synthesis. Extensive characterization revealed that nanostructured hydrogels were obtained and that small biomolecules, such as signaling peptides, could be attached on the surface. The final surfaces are bioactive and support endothelial cell attachment. Relevant biomimetic surfaces for bone tissue engineering could also be obtained from a sol-gel synthesized hydroxyapatite after immersion in different physiological media. The dissolution and posterior reprecipitation of the ions rendered a final apatite layer with a composition similar to that found in vivo. The experiments evidenced the importance of starting from a rather soluble material and, thus, pure hydroxyapatite was not able to promote apatite precipitation in vitro. This capacity has been related to the material bioactivity by many researchers in terms of its ability to bond to bone in tissue engineering applications. However, for tissue engineering a three-dimensional environment is required to build tissue-like constructs. A new model was developed based on the use of a very soft gel to obtain hard tissue. Although the concepts might seem to work in opposite directions, cells gain the ability to rapidly elongate and form a dense cellular network within this unrestrictive environment. Subsequent contraction of the whole system rendered a smaller and stronger final tissue-like construct. This system was considered biomimetic as it promotes high cell-cell interaction and cellular condensation, which are events that occur in bone and cartilage development. This system was extensively characterized with osteoprogenitor MC3T3-E1 cells that could undergo full osteogenic differentiation under chemical induction. More interestingly, the three-dimensional microenvironment was also able to promote by itself spontaneous expression of bone-related markers. Due to the interesting properties of this system, the same model was used to induce chondrogenic differentiation of human dermal fibroblasts. This cell type has been poorly explored for tissue engineering applications, but it might have great potential in future therapeutic platforms. This work provides proof of concept of chondrogenic potential of these cells in this three-dimensional system.

The extracellular matrix (ECM) of load-bearing soft tissues is characterized by a welldefined and complex architecture which is responsible for its high mechanical performance. Inspired by the native ECM of living tissues, we demonstrate the possibility to fabricate tough and cytocompatible hydrogels from a single polymeric precursor formulation and under physiological conditions. The designed systems were synthesized through an adapted Double-network (DN)-based methodology combining chemical and physical crosslinking mechanisms. Such multifunctional devices were able to withstand an impressive compressive stress in the same order of magnitude as the ones found in native load-bearing soft tissues, highlighting their potential for the repair of these tissues. Further improvements on the former DN-based hydrogel were made in order to achieve highly hydrated biomaterials with other advantageous properties for biomedical purposes, including self-healing and injectability. Inspired by the lotus-leaf liquid-repellence, our group proposed a simple, straightforward and cost-effective tool to produce spherical polymeric particles above artificial superantiwetting surfaces. In this thesis, this biomimetic strategy was used to fabricate a large variety of natural-based hydrogel spherical systems with distinct macroscopic structures. First, reversible superamphiphobic (SA) surfaces were fabricated by covering a substrate with specifically designed microcapsules entrapping magnetic particles. The main advantage of using magnetic responsive particles is the ability to control their arrangement and fixation over the substrate by applying an external magnetic field. The produced non-permanent SA surfaces were successfully employed to fabricate water/oil repellent surfaces, liquid marbles and microfluidic channels and, also used as templates for the fabrication of spherical particles. Second, SA surfaces were successfully employed as supports to produce spherical polymeric microparticles with potential as cell and drug carriers. The proposed strategy consists in spraying a hydrogel precursor solution over a SA surface followed by a crosslinking mechanism. Next, hierarchical systems were also created via the assembly of polymeric spherical particles induced by these artificial SA substrates under physiological conditions. Finally, SA surfaces were successfully employed to fabricate ready-to-use and stable liquefied capsules enclosing different objects, such as cells and drugs. All these bioinspired strategies are poised to usher the development of the next generation of engineered hydrogel devices for biomedicine and tissue engineering.
A matriz extracelular dos tecidos moles é caraterizada por uma estrutura definida e complexa, sendo responsável pelas suas extraordinárias propriedades mecânicas. Usando a matriz extracelular como inspiração, foi demonstrada a possibilidade de produzir hidrogéis robustos e citocompatíveis sob condições fisiológicas. Os materiais obtidos foram sintetizados através de uma adaptação da metodologia Double-network (DN), combinando mecanismos de reticulação físicos e químicos. Estes sistemas multifuncionais são capazes de suportar tensões mecânicas na mesma ordem de grandeza das encontradas nos tecidos estruturais do corpo, o que reforça o potencial destes biomateriais hidratados para reparar estes mesmos tecidos. Estes géis DN foram melhorados de modo a obter materiais com outras características importantes para aplicações biomédicas, nomeadamente a capacidade de se autorrepararem e serem administrados através de estratégias minimamente invasivas, como por injeção. Adicionalmente, o nosso grupo desenvolveu uma nova metodologia, inspirada pela capacidade de a folha de lótus repelir líquidos, para produzir partículas poliméricas com uma forma esférica. Esta técnica consiste em dispensar uma solução polimérica sobre uma superfície com extrema repelência a líquidos e, de seguida, um processo de reticulação é aplicado à gota polimérica de modo a reter a sua forma esférica. Nesta tese, esta estratégia biomimética foi usada para fabricar diversos sistemas esféricos com variadas estruturas macroscópicas. Primeiro, superfícies reversíveis e superanfifóbicas (SA) foram criadas através da deposição de microcápsulas contendo partículas magnéticas no seu interior sobre um suporte sólido. A principal vantagem de usar partículas sensíveis a campos magnéticos é a possibilidade de controlar a sua posição e fixação a um suporte usando um íman. Estas superfícies SA foram usadas como suportes para produzir partículas esféricas e canais de microfluídica. De seguida, partículas poliméricas com tamanhos na escala micrométrica foram obtidos, pela primeira vez, usando superfícies SA. A estratégia desenvolvida consiste em dispensar, sob uma superfície SA, uma solução polimérica usando um pulverizador e, de seguida, um mecanismo de reticulação é aplicado de modo a obter hidrogéis esféricos. Adicionalmente, foram também criadas partículas multicompartimentalizadas com uma estrutura hierárquica incorporando as micropartículas produzidas anteriormente. Finalmente, as superfícies SA foram também usadas para obter cápsulas esféricas compostas por uma camada externa polimérica e um núcleo no estado líquido. Diferentes objetos como células e moléculas bioativas podem ser encapsulados no interior das partículas anteriores, reforçando o seu potencial biomédico. É antecipado que todas estas estratégias biomiméticas sejam importantes para o desenvolvimento da nova geração de hidrogéis com potencial em biomedicina e engenharia de tecidos.
Programa Doutoral em Química

Animal flight represents a great challenge and model for biomimetic design efforts. Powered flight at low speeds requires not only appropriate lifting surfaces (wings) and actuator (engine), but also an advanced sensory control system to allow maneuvering in confined spaces, and take-off and landing. Millions of years of evolutionary tinkering has resulted in modern birds and bats, which are achieve controlled maneuvering flight as well as hovering and cruising flight with trans-continental non-stop migratory flights enduring several days in some bird species. Unsteady aerodynamic mechanisms allows for hovering and slow flight in insects, birds and bats, such as for example the delayed stall with a leading edge vortex used to enhance lift at slows speeds. By studying animal flight with the aim of mimicking key adaptations allowing flight as found in animals, engineers will be able to design micro air vehicles of similar capacities.

This chapter explores the potential of bio-inspiration in 3- and 4-D printing. The authors argue that the true potential of texturing hasn't been realized yet not because of the lack of enabling texturing technologies but because of the severe lack of detailed information about the functional details of texturing in a tribological situation, that is, how surface features, their geometry, interact with the functional gradients present within the subsurface layers to control the friction profile of a structure. The material emphasizes the potential of bio-inspired surfaces in providing a pathway for realizing true synchronization of function through a layer-by-layer customization of surface and subsurface material. In particular the chapter discusses methodologies to extract design parameters that lead to manifesting 4-D printed tribological constructs where surface and sub-surfaces respond optimally to external stimulants represented by the operation conditions of load, speed, and ambient temperature. Successful design of functional deterministic surfaces is not a product of mere biomimicry. Rather, it culminates probing the geometry, texture, form, and construction of the bio-analogue and linking these ingredients to the desired functional profile of the surface in the human engineering domain, that is, generation of bio-inspired functional surface designs stems from implementing design rules rather than replication of natural constructions. Deduction of design rules requires decoding the metrological features and the analysis of surface performance, of bio-analogues using standardized engineering methods. Success in designing a bio-inspired surface, therefore, requires a trans-disciplinary approach that combines engineering, physics, and biology. These don't combine naturally since they entail different methodologies of problem solving and investigations. It is hoped that this book would bridge the gap between the disciplines in the context of biomimetic surface design and construction. Further, it is hoped that the material would equip the reader with the basic skills needed to navigate between the biological and the engineering domains.

Micro-Electro-Mechanical-Systems (MEMS) are miniaturized devices that operate at small-scale. Actuators-based MEMS have not been commercially realized yet, owing to the manifestation of high surface forces such as adhesion and friction between their moving elements. In recent years, inspiration from ‘Lotus Effect' has opened a new direction in the field of micro/nano-tribology to manipulate/control surface forces at small-scale. The underlying principle discovered from the ‘super-hydrophobic nature' of the leaves of water-repellent plants has led to the design and development of various ‘biomimetic tribological surfaces' that exhibit remarkable reduction in surface forces under tribological contact. In this chapter are presented the tribological issues in MEMS devices, examples of conventional solutions for the tribological issues and unique ‘bioinspired solutions' that have great capability to mitigate surface forces at micro/nano-scales.

Micro-electro mechanical systems (MEMS) are miniaturized devices that operate at a small scale. Actuators-based MEMS have not been commercially realized yet, owing to the manifestation of high surface forces such as adhesion and friction between their moving elements. In recent years, inspiration from “Lotus Effect” has opened a new direction in the field of micro/nano-tribology to manipulate/control surface forces at small scale. The underlying principle discovered from the super-hydrophobic nature of the leaves of water-repellent plants has led to the design and development of various biomimetic tribological surfaces that exhibit remarkable reduction in surface forces under tribological contact. This chapter presents the tribological issues in MEMS devices, examples of conventional solutions for the tribological issues, and unique bioinspired solutions that have great capability to mitigate surface forces at micro/nano-scales.

“Green tribology” is the concept that was introduced in 2009 by the founder of Tribology, Prof. P. Jost, who defined it as “the science and technology of the tribological aspects of ecological balance and of environmental and biological impacts.” This includes tribological technology that mimics living nature (biomimetic surfaces) and thus is expected to be environment-friendly, the control of friction and wear that is of importance for energy conservation and conversion, environmental aspects of lubrication and surface modification techniques, and tribological aspects of green applications such as the wind-power turbines, tidal turbines, or solar panels. It is clear that a number of tribological problems could be put under the umbrella of “green tribology” and is of mutual benefit to one another. Biomimetic applications are of particular interest for the Green Tribology, because of their environment-friendliness. Nosonovsky and Bhushan suggested the “12 principles of the Green Tribology.” The common feature in various biomimetic surfaces is their hierarchical structure and the ability for self-organization. I will discuss the principles of self-organization in hierarchical tribological systems on the basis of the concepts of the non-equilibrium thermodynamics (the Onsager formalism). In particular, I will show that the thermodynamic approach in tribology can yield new and practically important results.

Humans can discriminate surface roughness using fingertip’s touch. It is believed that surface roughness is perceived by static and dynamic deformation of human skin. Recent findings have shown that subcutaneous slowly adapting mechanoreceptor (SA) detect static deformation of finger skin. However, there are difficulties to infinitely increase density of SA in limited skin space. [1] So, we focused on dynamic deformation is related with rapidly adapting mechanoreceptor (RA). In the process of scanning surface of objects with fingertips, RA detects vibrations induced by skin deformation. In this study, we suggest that sensors mimicking roles of RA can detect surface roughness. We used a polymer having similar characteristics of skin surface that transduce physical vibrations into electrical signal. And an array of polymer structures discriminates surface roughness. In other researches, they were tried to use one mechanoreceptor to acquire total range of vibrations. From the point of view which RAs have different vibration sensing ranges, we divided range of vibration through polymer structures and analyzed frequency element.

Internalization of pathogens inside pores and channels of fresh produce and formation of polymeric biofilm around their colonies are important phenomena in food safety due to complications they create for removal and inactivation of pathogens. The practical challenges does not allow for monitoring the pathogen-produce interaction in real time and under different ambient conditions. The present work introduces a biomimetic biosensing platform that simulates the actual produce and can detect the presence, growth and internalization of microorganisms and also potential formation of biofilm. The system consists of layers of capacitive electrodes made of polycrystalline silicon which are designed based on a standard foundry process (PolyMUMPs). The electrodes form multiple impedance-based biosensors and can simulate porous medium of the produce surface. As the cells reside on the surface of the top layer or penetrate inside the system, the capacitance value of each electrode pair changes. Monitoring the capacitance change of each biosensor allows us to determine where the microorganisms are and also whether their population is increasing. To demonstrate the applicability of our proposed biosensing system, a comprehensive FEM simulation is performed using ANSYS® APDL. The simulation results show that each pair of electrodes displays a specific pattern of capacitance change when cells reside on the system’s surface, move inside, grow or produce polymeric biofilm, because the electrostatic properties of cells and biofilm polymers are different from those of the solution. Analyzing the capacitance patterns allows us to determine that cells are at which stage of growth or internalization, and how far they have moved inside the system.

Tissue losses and organ failures result in more than 8 million surgical procedures each year in the United States. Current therapies for these disorders are seriously limited. Our laboratory takes a biomimetic approach to design polymers into body-part templates (scaffolds) to engineer tissues/organs. The scaffolds are designed to take the form of the missing/damaged body parts, to mimic certain advantageous aspects of natural extracellular matrix, and to contain certain designed structural features to enhance tissue regeneration. To mimic bone matrix, biodegradable polymer/nano-hydroxyapatite composite scaffolds have been developed. To mimic the nano-fibrous architecture of collagen, synthetic nano-fibrous scaffolds have been developed. To optimize scaffolding function, a variety of macropore networks have been designed in the nano-fibrous materials. These novel nano-structured scaffolds enhance cell adhesion and function. Surface engineering and biological delivery in the nano-fibrous scaffolds are shown to improve cellular interactions and tissue formation. These experimental results demonstrate that the biomimetic template design is a powerful approach for tissue regeneration.

Additive manufacturing technologies are being used to fabricate scaffolds with controlled architecture for tissue engineering applications. These technologies combined with computer-aided design systems enable to produce three-dimensional structures layer-by-layer in a multitude of materials. Actual prediction of the effective mechanical properties of scaffolds produced by Additive manufacturing systems, is very important for tissue engineering applications. One of the existing computer based techniques for scaffold design is topological optimisation. The goal of topological optimisation is to find the best use of material for a body that is subjected to either a single load or a multiple load distribution. This paper proposes a topological optimisation scheme based on existing micro-CT data in order to obtain the ideal topological architectures of scaffolds, maximising its mechanical behaviour under shear stress solicitations. This approach is based on micro-CT data of real biological tissues to create the loading (shear stress) and constraint surfaces of the scaffold during the topological optimisation process. This particular topological optimisation scheme uses the surface boundaries to produce novel models with different characteristics, which are different from the initial micro-CT models. This approach enables to produce valid biomimetic scaffold topologies for tissue engineering applications.

Osteochondral tissue is composed of ordered and random biological nanostructures and can, in principal, be classified as a nanocomposite material. Thus, the objective of this research is to develop a novel biomimetic biphasic nanocomposite scaffold via a series of 3D fabricating techniques for osteochondral tissue regeneration. For this purpose, a highly porous Poly(caprolactone) (PCL) bone layer with bone morphogenetic protein-2 (BMP-2)-encapsulated Poly(dioxanone) (PDO) nanospheres and nanocrystalline hydroxyapatite was photocrosslinked to a Poly(ethylene glycol)-diacrylate (PEG-DA) cartilage layer containing transforming growth factor-β1 (TGF-β1)-encapsulated PLGA nanospheres. Novel tissue-specific growth factor-encapsulated nanospheres were efficiently fabricated via a wet co-axial electrospraying technique. Integration and porosity of the distinct layers was achieved via co-porogen leaching and ultraviolet (UV) photocrosslinking of water soluble poly(ethylene glycol) (PEG) and <150 um sodium chloride salt particles providing greater control over pore size and increased surface area. Our in vitro results showed significantly improved human bone marrow derived mesenchymal stem cells (hMSCs) adhesion and differentiation in bone and cartilage layers, respectively. In addition, we are working on developing a novel table top stereolithography (SL) apparatus for the manufacture of custom designed 3D biomimetic scaffolds with incorporated growth factor encapsulated nanospheres for osteochondral defect repair. Our early-stage SL development has illustrated good corroboration between computer-aided design (CAD) and manufactured constructs with controlled geometry. The ultimate goal of the novel tabletop SL system is the manufacture of patient-specific implantable 3D nanocomposite scaffolds for osteochondral defect repair. The current SL system developed in our lab allows for efficient photocrosslinking of two novel nanocomposite polymeric materials for the manufacture of three-dimensional (3D) osteochondral constructs with good spatiotemporal control of growth factor release in addition to exhibiting similar mechanical properties to that of the native tissues being addressed.

With obesity being an increasing health concern, replacements of calorie-dense fat in diet is a necessity. Proteinaceous microgels have recently been found to have ultra-lubricating properties and are hypothesised to act as excellent fat replacers. However, such microgels have not been applied to more sustainable plant protein which is often associated with generating high friction in between oral contact surfaces and consequently generate astringency issues. The aim of this study was to design novel ultra-lubricating microgels using plant proteins and compare lubrication performance of various volume fractions (10-70 vol%) to that of a fat emulsion. An array of characterisation techniques combining oral tribology using 3D biomimetic tongue surface , rheology, dynamic light scattering (DLS), atomic force microscopy (AFM) and quartz crystal microbalance with dissipation (QCM-D) were used to characterise these newly designed microgels and their surface properties. Potato protein microgels at 5 and 10 wt% protein (PoPM5, PoPM10), pea protein microgel at 15 wt% protein (PePM15) and combined alternative protein microgel at 12.5 wt% (Po5:Pe7.5) were prepared at pH 7.0 by thermally crosslinking the proteins at 80°C for 30 minutes to form gels, followed by shearing. AFM and DLS revealed that microgels were sub-micron sized ranging in diameter from 85 to 232 nm with low polydispersity (‰¤ 0.25) . The microgels were relatively soft with storage modulus varying from 0.35 to 6.5 kPa. Irrespective of the type of proteins used, the microgel dispersions presented excellent lubrication performance especially owing to their adsorption properties as well as high effective viscosities. Strikingly, PePM15 microgels had similar friction coefficient values to that of the 20 wt% oil-in-water emulsion when introduced between 3D biomimetic tongue-like surface. Thus, we demonstrate for the first time that these sustainable protein microgels allow better incorporation of alternative protein in low calorie food without any negative mouthfeel consequences.

3-D culture has been shown to provide cells with a more physiologically authentic environment than traditional 2-D (planar) culture [1, 2]. 3-D cues allow cells to exhibit more realistic functions and behaviors, e.g., adhesion, spreading, migration, metabolic activity, and differentiation. Knowledge of changes in cell morphology, mechanics, and mobility in response to geometrical cues and topological stimuli is important for understanding normal and pathological cell development [3]. Microfabrication provides unique in vitro approaches to recapitulating in vivo conditions due to the ability to precisely control the cellular microenvironment [4, 5]. Microwell arrays have emerged as robust alternatives to traditional 2D cell culture substrates as they are relatively simple and compatible with existing laboratory techniques and instrumentation [6, 7]. In particular, microwells have been adopted as a biomimetic approach to modeling the unique micro-architecture of the epithelial lining of the gastrointestinal (GI) tract [8–10]. The inner (lumen-facing) surface of the intestine has a convoluted topography consisting of finger-like projections (villi) with deep well-like invaginations (crypts) between them. The dimensions of villi and crypts are on the order of hundreds of microns (100–700 μm in height and 50–250 μm in diameter) [11]. While microwells have proven important in the development of physiologically realistic in vitro models of human intestine, existing methods of ensuring their surface is suitable for cell culture are lacking. Sometimes it is desirable to selectively seed cells within microwells and confine or restrict them to the microwells in which they are seeded. Existing methods of patterning microwells for cell attachment either lack selectivity, meaning cells can adhere and migrate anywhere on the microwell array, i.e., inside microwells or outside of them, or necessitate sophisticated techniques such as micro-contact printing, which requires precise alignment and control to selectively pattern the bottoms of microwells for cell attachment [12, 13].