Bio-inspired 3D Research Articles

Bio-inspired powder bed fusion 3D printed surfaces for enhanced critical heat flux and boiling heat transfer

The thermal performance and sizing of two-phase heat exchangers employed in various industries can be significantly improved by modifying the surface topology of tubes. The advancement in metal 3D printing technology enables the modification of surfaces to generate distinct patterns that enhance the heat transfer coefficient. This study aligns with these advances by investigating the boiling heat transfer performance of 3D printed surfaces using methanol as the working fluid. The enhanced surfaces studied include four bio-inspired 3D printed surfaces (Mushroom, Cactus, Petal, and Torus), each strategically designed to improve the heat transfer coefficient (HTC) and delay the onset of critical heat flux (CHF). The primary objective of this research is to discuss and analyze the heat transfer mechanism in terms of bubble dynamics, particularly focusing on the interaction between surface morphology and bubble behavior. Experimental results reveal significant enhancements in CHF and HTC for 3D printed surfaces compared to plain surfaces. Among the 3D printed surfaces, the Mushroom surface exhibits the highest enhancement in CHF of 88 % compared to the plain surface. Similarly, the maximum HTC enhancements are 138 %, 86 %, 65 %, and 46 % for the Mushroom, Cactus, Petal, and Torus surfaces, respectively, compared to the plain surface. The methodologies and findings of this study are poised to have a lasting impact on the field, potentially opening new avenues for improving the efficiency and effectiveness of various two-phase heat exchangers.

Bio-inspired 3D printing of strain-hardening cementitious composites reticulated shell roofs

Inspired by the diving bell structure of the water spider, this study presents an innovative 3D printed strain-hardening cementitious composite (3DP-SHCC) reticulated shell roof. The compressive behavior of the 3DP-SHCC reticulated shell roof is evaluated using a combination of experimental tests and numerical simulation approaches. The 3DP-SHCC reticulated shell roof features excellent mechanical properties and an aesthetically pleasing appearance. The specific energy absorption and ductility index of this structure are 0.065 J/g and 0.078, respectively. The feasibility of this concept is validated by constructing a complete building structure within just 16 min. This printing process has the potential to create complex designs with minimal labor, making it suitable for rapid construction in extreme environments.

Self-Adhesive Electronic Skin with Bio-Inspired 3D Architecture for Mechanical Stimuli Monitoring and Human-Machine Interactions.

Recent development of wearable devices is revolutionizing the way of artificial electronic skins (E-skin), physiological health monitoring and human-machine interactions (HMI). However, challenge remains to fit flexible electronic devices to the human skin with conformal deformation and identifiable electrical feedback according to the mechanical stimuli. Herein, an adhesive E-skin is developed that can firmly attach on the human skin for mechanical stimuli perception. The laser-induced adhesive layer serves as the essential component to ensure the conformal attachment of E-skin on curved surface, which ensures the accurate conversion from mechanical deformation to precise electrical readouts. Especially, the 3D architecture facilitates the non-overlapping outputs that bi-directional joint bending and distinguishes strain/pressure. The optimized E-skin with bio-inspired micro-cilia exhibited significantly improved sensing performances with sensitivity of 0.652 kPa-1 in 0-4kPa and gauge factor of 8.13 for strain (0-15%) with robustness. Furthermore, the adhesive E-skin can distinguish inward/outward joint bending in non-overlapping behaviors, allowing the establishment of ternary system to expand communication capacity for logic outputs such as effective Morse code and intelligent control. It expects that the adhesive E-skin can serve as a functional bridge between human and electrical terminals for applications from daily mechanical monitoring to efficient HMI.

A simulated microgravity-oriented AIE probe-ECM hydrogel-integrated chip for cell culture and superoxide anion radical detection

Human space activities have been continuously increasing. Astronauts experiencing spaceflight are faced with health problems caused by special space environments such as microgravity, and the investigation of cell injury is fundamental. The development of a platform capable of cell culture and injury detection is the prerequisite for the investigation. Constructing a platform suitable for special conditions in space life science research is the key issue. The ground-based investigation is an indispensable part of the research. Accordingly, a simulated microgravity (SMG)-oriented integrated chip platform capable of 3D cell culture and in situ visual detection of superoxide anion radical (O2•−) is developed. SMG can cause oxidative stress in human cells, and O2•− is one of the signaling molecules. Thus, a O2•−-responsive aggregation-induced emission (AIE) probe is designed, which shows high selectivity and sensitivity to O2•−. Moreover, the probe exhibits abilities of long-term and wash-free staining to cells due to the AIE behavior, which is precious for space cell imaging. Meanwhile, a chip with a high-aspect-ratio chamber for adequate medium storage for the lack of the perfusion system during the SMG experiment and a cell culture chamber which can integrate the extracellular matrix (ECM) hydrogel for the bioinspired 3D cell culture is fabricated. In addition, a porous membrane is introduced between the chambers to prevent the hydrogel from separating during the SMG experiment. The afforded AIE probe-ECM hydrogel-integrated chip can achieve 3D culturing of U87-MG cells and in situ fluorescent detection of endogenous O2•− in the cells after long-term staining under SMG. The chip provides a powerful and potential platform for ground-based investigation in space life science and biomedical research.

Advanced 3D-printed PVDF/BT piezoelectric energy harvester with a bio-inspired 3D structure for a self-powered smart mouse

Piezoelectric polymers such as poly(vinylidene fluoride) (PVDF) exhibit remarkable flexibility, lightweight, durability, and biocompatibility compared to their ceramic counterparts. This unique characteristic makes them highly suitable for harvesting mechanical vibrations. However, conventional manufacturing methods mainly result in two-dimensional (2D) piezoelectric energy harvester (PEHs) structures. This confines the internal stress and, as a result, limits their potential voltage output. This study introduces an innovative bio-inspired three-dimensional (3D) structure crafted through fused deposition modeling (FDM). Barium titanate (BT) nanoparticles were added as piezoelectric fillers to improve the performance of the PEH. The obtained nanocomposite was poled under optimal poling conditions, achieving a β-phase fraction of 95,72 %, a piezoelectric charge coefficient (d33) of 28 pC/N, and a permittivity of 24.2 at 100 Hz. A parametric study was performed through numerical analysis, resulting in an effective and optimized structural configuration. The combined excellent piezoelectric properties of the nanocomposite with the optimized structure enabled the PEH to generate an open-circuit voltage of 30.8 V, enabling it to charge a commercial 1 μF capacitor to 25 V in just 260 s. The bioinspired PEH demonstrates its practical application by powering an innovative device known as the "smart mouse," showcasing its utility and potential in real-world applications.

Cyborg insect repeatable self-righting locomotion assistance using bio-inspired 3D printed artificial limb

Cyborg insects have emerged as a promising solution for rescue missions, owing to their distinctive and advantageous mobility characteristics. These insects are outfitted with electronic backpacks affixed to their anatomical structures, which endow them with imperative communication, sensing, and control capabilities essential for effecting survivor retrieval. Nevertheless, the attachment of supplementary loads to the insect’s body can exert adverse effects on their intrinsic self-righting locomotion when confronted with fall or shock scenarios. To address this challenge, the present study introduces a bio-inspired 3D-printed artificial limb that serves to facilitate the maneuverability of cyborg insects amidst unpredictable conditions. Drawing inspiration from the natural self-righting motion exhibited by Coccinellidae, we have successfully identified a solution that can be transferred to the electronic backpack utilized by G. portentosa. Incorporation of the bio-inspired artificial wing-like limb has notably enabled the cyborg insect to achieve a remarkable tilting angle of 112°, thereby significantly amplifying the success ratio of self-righting under conditions closely emulating those prevalent in disaster areas. Moreover, we have replicated the expansion and contraction kinematics to ensure seamless motion progression within confined spaces. Importantly, the fabricated device proffered in this study has been meticulously designed for facile reproducibility employing commonly available tools, thereby serving as an inspirational catalyst for fellow researchers engaged in the advancement of 3D-printed limb development aimed at expanding the functional capacities of cyborg insects.

A bio-inspired silkworm 3D cocoon-like hierarchical self-assembled structure from π-conjugated natural aromatic amino acids.

The formation of spontaneous 3D self-assembled hierarchical structures from 1D nanofibers is a significant breakthrough in materials science. Overcoming the major challenges associated with developing these 3D structures, such as uncontrolled self-assembly, complex procedures, and machinery, has been a formidable task. However, the current discovery reveals that simple π-system (fluorenyl)-functionalized natural aromatic amino acids, phenylalanine (Fmoc-F) and tyrosine (Fmoc-Y), can form bio-inspired 3D cocoon-like structures. These structures are composed of entangled 1D nanofibers created through supramolecular self-assembly using a straightforward one-step process of solvent casting. The self-assembly process relies on π-π stacking of the fluorenyl (π-system) moieties and intermolecular hydrogen bonding between urethane amide groups. The cocoon-like structures are versatile and independent of concentration, temperature, and humidity, making them suitable for various applications. This discovery has profound implications for materials science and the developed advanced biomaterials, such as Fmoc-F and Fmoc-Y, can serve as flexible foundational components for constructing 3D fiber-based structures.

Bio-inspired 3D printing of layered structures utilizing stabilized amorphous calcium carbonate within biodegradable matrices

The formation of bio-inspired 3D printed layered structures from amorphous calcium carbonate offer a new approach for 3D printing of ceramic materials.

Bioinspired 3D flexible devices and functional systems.

Flexible devices and functional systems with elaborated three-dimensional (3D) architectures can endow better mechanical/electrical performances, more design freedom, and unique functionalities, when compared to their two-dimensional (2D) counterparts. Such 3D flexible devices/systems are rapidly evolving in three primary directions, including the miniaturization, the increasingly merged physical/artificial intelligence and the enhanced adaptability and capabilities of heterogeneous integration. Intractable challenges exist in this emerging research area, such as relatively poor controllability in the locomotion of soft robotic systems, mismatch of bioelectronic interfaces, and signal coupling in multi-parameter sensing. By virtue of long-time-optimized materials, structures and processes, natural organisms provide rich sources of inspiration to address these challenges, enabling the design and manufacture of many bioinspired 3D flexible devices/systems. In this Review, we focus on bioinspired 3D flexible devices and functional systems, and summarize their representative design concepts, manufacturing methods, principles of structure-function relationship and broad-ranging applications. Discussions on existing challenges, potential solutions and future opportunities are also provided to usher in further research efforts toward realizing bioinspired 3D flexible devices/systems with precisely programmed shapes, enhanced mechanical/electrical performances, and high-level physical/artificial intelligence.

Bio-inspired, biodegradable, and fluffy 3D PLA fibrous sponges with dynamic fractal nano-sweepers for on-demand oil/water separation

Frequent oil leakage results in a huge waste of fossil fuel resources and severely threatens the global water-waste-energy nexus. Membrane separation technology is a promising effective and energy-saving approach for recycling waste oil resources and oily-environment remediation. Despite many bioinspired materials with the mitigated selectivity/permeability trade-off having been developed, a significant issue has been ignored, that is, most of the membranes are non-biodegradable and could cause secondary environmental pollution. In this work, inspired by the natural 3D coral organisms with sustainable fiber tentacles; we propose a biomimetic crystal-engineering strategy of space-confined solvent-induced recrystallization to prepare a 3D biodegradable PLA fibrous sponge with coral-like nanoflower/honeycomb sweeper arrays. By virtue of the coral-like nanoporous fractal arrays with superhydrophobicity and proactive fouling resistance, the resulting PLA sponge exhibits excellent separation performance of immiscible oil–water mixtures (ultrahigh permeation flux of up to 27,908 L m-2h−1) and water-in-oil emulsions (high separation efficiency of up to 99.9 %). Significantly, with the advantage of biodegradability and recyclability of PLA, we envision such environmentally friendly PLA fibrous sponges would show promising potential in the fields of environmental remediation, oil recovery, self-cleaning, etc.

Development of in vitro cardiovascular tissue models within capillary circuit microfluidic devices fabricated with 3D stereolithography printing

This study presents the development and morphology analysis of bioinspired 3D cardiovascular tissue models cultured within a dynamic capillary circuit microfluidic device. This study is significant because our in vitro 3D cardiovascular tissue models retained within a capillary circuit microfluidic device provide a less expensive, more controlled, and reproducible platform for more physiologically-relevant evaluation of cellular response to microenvironmental stimuli. The overall aim of our study is to demonstrate our cardiovascular tissue model (CTM) and vascular tissue model (VTM) actively changed their cellular morphology and exhibited structural reorganization in response to biophysical stimuli provided by microposts within the device tissue culture chambers during a 5-day period. The microfluidic device in this study was designed with the Young–Laplace and Navier–Stokes principles of capillary driven fluid flow and fabricated with 3D stereolithography (SLA) printing. The cardiac tissue model and vascular tissue model presented in this study were developed by encapsulating AC16 cardiomyocytes (CTM) and Human umbilical vein endothelial cells (VTM) in a fibrin hydrogel which were subsequently loaded into a capillary circuit microfluidic device. The cardiovascular tissue models were analyzed with fluorescent microscopy for morphological differences, average tube length, and cell orientation. We determined the VTM displayed capillary-like tube formation and the cells within both cardiovascular tissue models continued to elongate around microposts by day-5 which indicates the microfluidic system provided biophysical cues to guide cell structure and direction-specific organization.

Modeling and design of heterogeneous hierarchical bioinspired spider web structures using deep learning and additive manufacturing

Spider webs are incredible biological structures, comprising thin but strong silk filament and arranged into complex hierarchical architectures with striking mechanical properties (e.g., lightweight but high strength, achieving diverse mechanical responses). While simple 2D orb webs can easily be mimicked, the modeling and synthesis of 3D-based web structures remain challenging, partly due to the rich set of design features. Here, we provide a detailed analysis of the heterogeneous graph structures of spider webs and use deep learning as a way to model and then synthesize artificial, bioinspired 3D web structures. The generative models are conditioned based on key geometric parameters (including average edge length, number of nodes, average node degree, and others). To identify graph construction principles, we use inductive representation sampling of large experimentally determined spider web graphs, to yield a dataset that is used to train three conditional generative models: 1) an analog diffusion model inspired by nonequilibrium thermodynamics, with sparse neighbor representation; 2) a discrete diffusion model with full neighbor representation; and 3) an autoregressive transformer architecture with full neighbor representation. All three models are scalable, produce complex, de novo bioinspired spider web mimics, and successfully construct graphs that meet the design objectives. We further propose an algorithm that assembles web samples produced by the generative models into larger-scale structures based on a series of geometric design targets, including helical and parametric shapes, mimicking, and extending natural design principles toward integration with diverging engineering objectives. Several webs are manufactured using 3D printing and tested to assess mechanical properties.

Bioinspired urchin-like murray carbon nanostructure with protection shell for advanced lithium-sulfur batteries

Commercial application of lithium-sulfur (Li-S) batteries is hindered by the insulating nature of sulfur and the dissolution of polysulfides. Here, a bioinspired 3D urchin-like N-doped Murray’s carbon nanostructure (N-MCN) with interconnected micro-meso-macroporous structure and a polydopamine protection shell has been designed as an effective sulfur host for high-performance Li-S batteries. The advanced 3D hierarchically porous framework with the characteristics of the generalized Murray’s law largely improves electrolyte diffusion, facilitates electrons/ions transfer and provides strong chemisorption for active species, leading to the synergistic structural and chemical confinement of polysulfides. As a result, the obtained P@S/N-MCN electrode with high areal sulfur loading demonstrates high capacity at high current densities after long cycles. This work reveals that following the generalized Murray’s law is feasible to design high-performance sulfur cathode materials for potentially practical Li-S battery applications.

Prediction and experimental validation approach to improve performance of novel hybrid bio-inspired 3D printed lattice structures using artificial neural networks

Novel Cellular lattice structures with lightweight designs are gaining more interest in the automobile and aerospace sectors. Additive manufacturing technologies have focused on designing and manufacturing cellular structures in recent years, increasing the versatility of these structures because of the significant benefits like high strength-to-weight ratio. In this research, a novel hybrid type of cellular lattice structure is designed, bio-inspired from the circular patterns seen in the bamboo tree structure and the overlapping patterns found on the dermal layers of fish-like species. The unit lattice cell with varied overlapping areas with a unit cell wall thickness of 0.4 to 0.6 mm. Fusion 360 software models the lattice structures with a constant volume of 40 × 40 × 40 mm. Utilizing the stereolithography (SLA) process and a vat polymerization type three-dimensional printing equipment is used to fabricate the 3D printed specimens. A quasi-static compression test was carried out on all 3D printed specimens, and the energy absorption capacity of each structure was calculated. Machine learning technique like the Artificial neural network (ANN) with Levenberg–Marquardt Algorithm (ANN-LM) was applied to the present research to predict the energy absorption of the lattice structure with parameters such as overlapping area, wall thickness, and size of the unit cell. The k-fold cross-validation technique was applied in the training phase to get the best training results. Overall, the results obtained using the ANN tool are validated and can be a favourable tool for lattice energy prediction with available data.

Crack modes and toughening strategies of bioinspired 3D printed double-helicoidal architectures

The crack modes and toughening strategies of 3D printed double-helicoidal (DH) composites were fully characterized by performing quasi-static three-point bending experiments and simulations. Notch-containing DH specimens were fabricated with dual-material curing 3D printer PolyJet technology, while single-helicoidal (SH) specimens were also prepared for comparison. The rigid glassy polymer VeroWhite and the soft rubbery polymer TangoBlackPlus were selected as the brick and adhesive of the specimens, respectively. First, the crack propagation path of the specimens under three-point bending loading was observed, and the fracture toughness and critical deformation displacements were calculated. The double twisting pattern of DH composite makes cracks deflect along complex deflection paths, resulting in increased energy dissipation required to produce deflected crack surfaces, which delays catastrophic damage. Then, the deformation and interlayer stress distribution under static loading were analyzed by finite element analysis. It was found that the interlaminar shear stresses σ13 and σ23 generated in adjacent layers were responsible for the crack deflection of the DH specimens. Toughening mechanisms of the DH structure inspired by coelacanth will promote the design of next generation fracture-resistant composites.

Marine-Inspired Approaches as a Smart Tool to Face Osteochondral Regeneration.

The degeneration of osteochondral tissue represents one of the major causes of disability in modern society and it is expected to fuel the demand for new solutions to repair and regenerate the damaged articular joints. In particular, osteoarthritis (OA) is the most common complication in articular diseases and a leading cause of chronic disability affecting a steady increasing number of people. The regeneration of osteochondral (OC) defects is one of the most challenging tasks in orthopedics since this anatomical region is composed of different tissues, characterized by antithetic features and functionalities, in tight connection to work together as a joint. The altered structural and mechanical joint environment impairs the natural tissue metabolism, thus making OC regeneration even more challenging. In this scenario, marine-derived ingredients elicit ever-increased interest for biomedical applications as a result of their outstanding mechanical and multiple biologic properties. The review highlights the possibility to exploit such unique features using a combination of bio-inspired synthesis process and 3D manufacturing technologies, relevant to generate compositionally and structurally graded hybrid constructs reproducing the smart architecture and biomechanical functions of natural OC regions.

Bio-inspired design, modeling, and 3D printing of lattice-based scale model scooter decks

This research aims at enhancing the performance of scale-model scooter decks by investigating various architected cellular metamaterial and bio-inspired core structure designs, such as honeycomb, tetrachiral, re-entrant, arrowhead, and star-shaped arrangements. An initial effort is made toward the design and rapid prototyping of small-scale deck with a uniform honeycomb core structure. More specifically, polylactic acid is utilized to fabricate complex structures via fused filament fabrication technique. Investigation is then focused on its mechanical performance, such as its bending properties obtained through a three-point bending test. Simulations are also conducted with different core configurations using a geometrically non-linear finite element method which is implemented. Experiments are carried out to verify the numerical results. After validation, various patterns are modeled, and eventually, it is observed that the functionally graded arrowhead structure has the best bending resistance, compared to other bio-inspired and mechanical metamaterial structures. At a constant force of 845 N, the functionally graded arrowhead design lowers the deflection in the middle of the scale model of scooter deck by up to 14.7%, compared to the uniform arrowhead structure. Furthermore, comparing the tetrachiral and functionally graded arrowhead configurations at a constant force, a 30% reduction in central deflection was observed. Due to the lack of similar results and designs in the specialized literature, this work could potentially advance the state-of-the-art scooter core designs and provide designers with architectures that could enhance the performance and safety of scooters.

An experimental and numerical investigation on the performance of novel hybrid bio-inspired 3D printed lattice structures for stiffness and energy absorption applications

The modern additive manufacturing process enables the fabrication of innovative structural designs of lattice structures with enhanced mechanical properties. Characterizing the designability of lattice geometries and the corresponding mechanical performance, particularly the compressive strength is vital to commercializing lattice structures for lightweight components. In this paper, a Novel hybrid type of lattice structure was developed inspired by the overlapping pattern of scales on dermal layers of the species like fish and circular patterns observed from the bamboo tree structure. This research designed the lattice cell with 20%,30%,40%, and 50% overlapping areas based on the proposed circular area. The unit cell wall thickness varies between 0.4 mm and 0.6 mm. The designed structures with a constant volume of 40x40x40 mm, varied circular diameters, overlapping areas, and unit wall thickness are modeled in Fusion 360 software. 3D-printed lattice structures were fabricated using the vat polymerization type three-dimensional printing machine using the principle of stereolithography (SLA) technique. Then, the 3D-printed specimens are tested for quasi-static compressive response in a universal testing machine (UTM) by following ASTM standards. The test results are evaluated and compared with the simulation results. Finally, the best lattice structure is selected for energy absorption application in the aerospace and defense sectors.

3D Printed Hollow Microneedles for Treating Skin Wrinkles Using Different Anti-Wrinkle Agents: A Possible Futuristic Approach

Skin wrinkles are an inevitable phenomenon that is brought about by aging due to the degradation of scleroprotein fibers and significant collagen reduction, which is the fundamental basis of anti-wrinkle technology in use today. Conventional treatments such as lasering and Botulinum toxin have some drawbacks including allergic skin reactions, cumbersome treatment procedures, and inefficient penetration of the anti-wrinkle products into the skin due to the high resistance of stratum corneum. Bearing this in mind, the cosmetic industry has exploited the patient-compliant technology of microneedles (MNs) to treat skin wrinkles, developing several products based on solid and dissolvable MNs incorporated with antiwrinkle formulations. However, drug administration via these MNs is limited by the high molecular weight of the drugs. Hollow MNs (HMNs) can deliver a wider array of active agents, but that is a relatively unexplored area in the context of antiwrinkle technology. To address this gap, we discuss the possibility of bioinspired 3D printed HMNs in treating skin wrinkles in this paper. We compare the previous and current anti-wrinkling treatment options, as well as the techniques and challenges involved with its manufacture and commercialization.

Numerical investigations on mechanical properties of bio-inspired 3D printed geometries using multi-jet fusion process

PurposeThe purpose of this study is to find the best geometries among the cylindrical, enamel and honeycomb geometries based upon the mechanical properties (tensile test, compression test and shear test). Further this obtained geometry could be used to fabricate products like exoskeleton and its supporting members.Design/methodology/approachThe present research focuses on the mechanical testing of cylindrical, enamel and honeycomb-shaped parts fabricated through multi-jet printing (MJP) process with a wall thickness of 0.26, 0.33, 0.4 and 0.66 mm. The polymer specimens (for tensile, compression and shear tests) were fabricated using a multi-jet fusion process. The experimental results were compared with the numerical modelling. Finally, the optimal geometry was obtained, and the influence of wall thicknesses on various mechanical properties (tensile, compression and shear) was studied.FindingsIn comparison to cylindrical, enamel structures the honeycomb structures required less time to fabricate and had lower tensile, compressive and shear strengths. The most efficient geometry for fully functional parts where tensile, compressive and shear forces are present during application – cylindrical geometry is preferred followed by enamel, and then honeycomb. It was found that as the wall thickness of various geometries was increased, their ability to withstand tensile, compressive and shear loads also enhanced. The enamel shape structure exhibits greater strain energy storage capacity than other shape structures for compressive loads, and the strength to resist the compressive load will be lower. In the case of cylindrical geometries for tensile loading, the resisting area toward the loading will be higher in comparison to honeycomb- and enamel-based structures. At the same time, the ability to store the stain energy is less. The results of the tensile, compression and shear load finite element analysis using ANSYS are in agreement with those of the experiments.Originality/valueFrom the insight of literature review, it is found that a wide range of work is done on fused deposition modeling (FDM) process. But in comparison to FDM, the MJP provide the better dimensional accuracy and surface properties (Lee et al., 2020). Therefore, it is observed that past research works not incorporated the effect of wall thickness of the embedded geometries on mechanical properties of the part fabricated on MJP (Gibson, n.d.). Hence, in this work, effect of wall thickness on tensile, compression and shear strength is considered as the main factor for the honeycomb, enamel and cylindrical geometries.