Bioinspiration, Biomimetics, and Bioreplication XIV

Metamaterials are artificially engineered structures that can exhibit unconventional properties not easily observed in nature. These unique architectures offer a robust platform for manipulating acoustic or elastic wave properties for energy localization and focusing, thus broadening their potential applications in energy harvesting and sensing. I will provide a comprehensive overview of the latest breakthroughs in the design of phononic crystals and acoustic metamaterials. These advancements promise a substantial enhancement in energy harvesting performance when these materials are integrated with piezoelectric components. In addition to wave-based metamaterials, I will summarize our recent advances in vibration energy harvesting, sensing, and energy absorption applications, facilitated by the exciting field of mechanical metamaterials. These materials feature meta-atoms that respond to external stimuli, collectively displaying extraordinary material properties like negative stiffness, Poisson's ratio, and multistability. Notably, these architectures are not constrained by dynamic wavelength dependence, offering broader design opportunities across multiple scales.

Fabric-based exosuits, for VR body haptics or to generate muscular assistance, require compliant, efficient, fast, lightweight yet high-force actuators. Much prior work has focused on pneumatic principles, an effective solution, but that needs an external pump or compressor. I will present several electrically-driven fiber-format flexible actuators developed in my lab. Making actuators shaped like fibers is key to their integration in active textiles. Our devices operate on electrostatic principles, which offers high energy density and high efficiency. I report fiber-format pumps, 2 mm in diameter and several meters in length, that generate fluid flow with no moving parts, and can be woven into fabrics, allowing both thermal management and shape change. I also report fiber-shaped electrostatic sliding stepper motors, 4 mm in diameter, that serve as long thin muscles to power gloves for VR and back-support exoskeletons. I will discuss open challenges and opportunities in making active wearables.

Cutting-edge research is currently centered on the development of spectrally selective dynamic solutions, drawing inspiration from the self-cooling ability observed in butterflies. These innovative materials emit thermal radiation and passively cool themselves below ambient temperature. This ability holds significant promise for addressing surface overheating in urban environments, as they can selectively emit thermal radiation towards the atmospheric windows, effectively radiating heat towards the cooler sky temperature under clear sky conditions. Despite their potential, practical adoption of these materials faces hurdles due to the lack of accessible characterization processes and metrics for accurately quantifying their thermal benefits. Consequently, this paper focuses on the development of a scalable experimental protocol, which not only facilitates material development but also dynamic testing under realistic environmental conditions. The outcomes of this research are presented through a novel index, which, for the first time, considers the unique potential of extra radiative exchange inherent to selective radiative cooling, inspired by nature.

Inspired by the morphological disorder that underlies the exhibition of circular-polarization-state-sensitive color by the exocuticle in many beetle species, the concept of disordered chirality was theoretically explored. The disordered chiral structure chosen is one wherein each helical turn may be different from its adjacent helical turns. The boundary-value problem of reflection and transmission of a normally incident plane wave by a disordered chiral structure was solved. Numerical results indicate the remarkable resilience of circular-polarization-state-selective reflection.

Fish scale-like structures on substrates, arranged periodically, work together to create unique mechanical and optical behaviors. These include nonlinear stiffness, anisotropic deformation, and eventually, locking behavior. Fabrication of scale-like biomimetic examples involves embedding stiffer, plate-like sections into softer substrates. Previously, research has focused on their static qualities. The dynamic response is just as fascinating, showing remarkable interplay between geometry and materials, along with anisotropies. The damping behavior observed here significantly diverges from the conventional damping seen in mechanical frameworks, often modeled as Rayleigh damping. Here we discuss the origin of some of these behaviors that include material-geometry distinction in damping, multiple damping modes and interplay of dissipation possibilities. We have shown a derivation of simple mathematical laws estimating nonlinear spring damper system that govern architecture-dissipation relationships and can help guide design. We conclude by noting the different type of structural damping with other forms of dissipation typically encountered in mechanical behavior.

In the field of wildlife preservation, organisms rely on natural defenses to protect against environmental factors. Similarly, textiles serve as our shield against external elements in daily life. Our research aims to develop multifunctional textiles with antimicrobial and self-cleaning properties while maintaining the original fabric's integrity. We focus on common organic textiles, enhancing them with metal oxides through low-temperature Vapor Phase Infiltration. We infiltrate cotton and polyethylene fabrics with ZnO. These textiles exhibit self-cleaning features and demonstrate photocatalytic abilities when exposed to sunlight. They are also effective against Gram+ and Gram- bacteria. Additionally, we investigate the durability of the infiltration during laundering.

Many current insect-scale robots, like Robo-bee and Robofly, are limited to single modes of locomotion due to size and power constraints. In contrast, grasshoppers excel in multi-modal locomotion, efficiently moving through crawling, jumping, and flying. They even employ gliding during flight for energy conservation. Grasshoppers offer valuable inspiration for micro-scale robots, particularly in transitioning from land to air mobility through deployable wings. This study examined Schistocerca americana grasshopper wings to understand their aerodynamics and transition dynamics. A simplified corrugated wing model, based on CT-scanned wings, was analyzed for aerodynamics. A grasshopper-inspired glider, incorporating similar wing features, was flight-tested using VICON Tracker to assess kinematics and aerodynamic efficiency. This glider's performance was compared with one using an engineered airfoil. Additionally, the study explored the transition dynamics of grasshopper hind wings, examining axillary sclerite and fold lines using Quanta 200 FE-ESEM. These findings hold promise for enhancing insect-scale robotics with versatile locomotion capabilities.

In this paper, a biomimetic quadrupedal robot with origami cylinder actuators as legs is introduced. The quadrupedal robot mimicked locomotion of four-legged animals. The robot had Kresling-patterned origami cylinder as legs and adopted a bounding gait for the locomotion. A tendon-driven actuation method was utilized for the movement of the origami cylinders. The origami cylinder actuators were controlled via predefined operation signals for the bounding gait. An operating condition was defined heuristically, by conducting tests in various conditions. At the operating condition, the robot moved as the speed of 0.28 body length per second. Specifically, the locomotion of the robot was analyzed by dividing the gait into multiple phases.

Avian species change their inertia tensor to manipulate their stability and control properties by various wing morphing motions. This motivates consideration of sweep changes in winged uninhabited air vehicles (UAV). Here we examine using distributed wing sweep to via a system of shape memory alloy (SMA) cells to perform changes in stability and agility of a winged UAV. By using a cell configuration of SMA activated structures, much like a metamaterial, relatively large changes in sweep can be obtained. Here we focus on the dynamics and stability of such a configuration.

This work highlights advancements in a bat-like robot employing Shape Memory Alloy (SMA) micro-wires in conjunction with a compliant beam joint, designed to operate within a determined resonance frequency. This novel approach has unlocked new performance enhancements, maintaining substantial wing-span at frequencies (5-7 Hz) higher than the usual limited actuating cycling speeds of SMAs. The results were achieved without any external cooling, and present higher energy efficiency than normal rotational hinge joints. These new results are meant to expand the horizons of innovative aero-robotic biomimicry solutions, pointing also in direction of more energy-efficient and faster SMA wire actuation.

Birds are outstanding flyers with high aerodynamic efficiency and agility, especially under dynamic flight conditions. Flight feathers play a key role in achieving these remarkable performances based on their flexible and hierarchical structures. To develop bio-inspired micro air vehicles (MAVs), researchers have adopted rigid feather-shaped panels, membrane-type artificial feathers and natural feathers as part of the morphing wing platform. In this paper, bio-inspired, 3D printed feathers with hierarchical structures resembling natural flight feathers are presented. Moreover, piezoresistive and piezoelectric sensing components are embedded in the 3D printed feather rachis, which can provide sensory information on the aerodynamic forces and vibrations after instrumented on wings.

Mangroves root in saltwater and provide cool shelters that sustain an incredible ecosystem. Here, we demonstrate a mangrove-inspired approach to cooling in hot climates. Light-induced evaporation of saltwater occurs through a capillary wick composed of drop-cast microparticles. Saltwater evaporation rates are significantly higher than expected and are accelerated via light illumination. Our results point to significant potential for this interface-driven approach in solar non-thermal desalination and water separation technologies, as well as heat cooling shelters in dry climates.

In this paper, we designed a novel bionic prosthetic foot mimicking human plantar muscle biomechanics to restore natural gait mechanics for lower limb amputees. In addition, energy harvesting technology was exploited to capture energy from the deformation of the prosthetic foot to power the wearable electronics to monitor the users' motion. Specifically, piezoelectric transducers were attached to the prosthetic foot to generate electricity when the ground reaction force deformed the prosthetic foot during the stance phase. Finite element analysis in the ANSYS platform was conducted to analyze the deformations of the prosthetic foot. Finally, a prototype was fabricated and tested on a unilateral below-knee amputee to validate our design. The subject's gait and the piezoelectric transducers' energy output were logged and studied.

Biofilms, a complex aggregation of pathogenic bacteria shielded by a biopolymer matrix, pose a significant challenge in treating chronic wounds. Transdermal drug delivery, including microneedle patch, has shown promise in treating biofilms. However, drug diffusion is limited by microneedle structure, material, design, distribution, and drug molecule diffusion coefficient. In this study, an ultrasound-based drug delivery patch, featuring a microneedle array and piezoelectric transducer (PZT) for precise, promptly delivery of drugs directly into the biofilm, is proposed. The microneedles, loaded with drugs, pierce the biofilm, while the PZT generates ultrasonic waves, producing localized acoustic pressure and streaming fields that facilitate drug distribution. The comprehensive study of critical parameters including ultrasound intensity and frequency on temperature variation is investigated. The physical mechanisms governing drug distribution and particle manipulation of various sizes is explored. With its robust applicability and versatility, the proposed drug delivery system holds great promise for tackling diverse medical challenges beyond chronic wounds.

The Asian citrus psyllid (ACP), Diaphorina citri Kuwayama (Hemiptera: Liviidae), is a citrus pest that vectors the bacterium that causes huanglongbing (HLB) disease between citrus trees. It has become a very large problem to the US citrus growers. Male ACP find females by vibrating the substrate (branch) to call them. The females vibrate a response and the males track these responses to find them in a citrus tree. We have created three ACP call recognition systems–one using Matlab, one using TensorFlow implemented on a Raspberry Pi, and one using Edge Impulse implemented on a RP2040 microcontroller. All three systems recognized calls with an accuracy greater than 79.5%. A demonstration on a single, long recording of two ACP vibrating to each other using the RP2040 system shows that it would be useful in a live implementation.

Optical fibers are one example of waveguides that can transmit multi-modal information. This information can be encoded in different optical modes in a multi-mode fiber or in different types of modes. For example, optical fibers have also recently been demonstrated to be excellent waveguide for acoustic modes. This means that sensing does not have to be performed at the location that the optical fiber is bonded to the structure, but instead Lamb waves can be converted into propagating acoustic modes in optical fibers. These modes can be transmitted to different sensor locations within the optical fiber. This presentation discusses the physical characteristics of these optical fiber acoustic modes and their use to increase the signal to noise ratio of the collection of Lamb wave information. Experimental verifications of the physical behavior of these modes using micro-laser Doppler vibrometry is also presented.

Metal additive manufacturing (AM) has experienced an explosive growth in interest within the aerospace and space sectors, but the adoption in real application has lagged interest. Process qualification (or lack thereof) is the primary reason and to date in situ sensing has failed to make a substantial impact, despite obvious utility. The primary premise of this talk is that current sensing techniques used in industry lag significantly behind what is possible and already implemented in other industries, and proper focus and division of labor between academia and industry can remedy the situation. Through this discourse we will assess whether or not current sensors used in AM are sufficient, what roadblocks may exist for academia to assist in developing solutions for industry, and how the in situ sensing community should focus their efforts for maximum impact.

Nature’s exquisite designs are a constant source of inspiration for materials scientists, yet our ability to replicate biological interactions in engineered materials is often limited. A major obstacle in exploiting biological interactions in macroscale materials is a lack of understanding of how environmental changes affect intrinsic molecular functionality and, ultimately impact macroscale behaviour. From a material design standpoint bacterial adhesins, cell surface proteins allowing bacteria to bind to, and colonise, a host, are particularly interesting. Many of these adhesins exhibit so-called ‘catch bond’ behaviour, in which the adhesive force of their receptor-ligand complexes increases, rather than decreases, at high shear. Transplanting catch bond-forming protein complexes onto polysaccharide chains opens up the possibility of creating bio-based hydrogel networks with unique tensile properties. The exploration of catch bond complexes from the molecular to the macroscale and the applications of catch bond mediated polymer networks in biomedical engineering will be the focus of this talk.

Morpho butterfly’s blue is well known, but, mysterious. This is because its single blue color in wide angles is produced by interference from an ORDERED nanostructure that should produce the rainbow angular dependence. This mystery is attributed to a specific nanostructure having both ORDER and DISORDER. Converting this reflective principle to transmission, we have proposed a new daylight window with high transmittance, wide angular spread, and low color dispersion, which have been impossible to meet simultaneously because of their trade-off relationship. Although our originally proposed nanostructure was difficult to fabricate, we have designed, fabricated, and demonstrated a new structure to solve the problem.

Natural processes seek to advance structures and materials. Hybridizing materials, that is, merging organic and inorganic elements, provides opportunities for such advancement. Our vapor phase processes enhance mechanical and electronic properties of polymeric materials through hybridization. This results in improved properties and new functionalities, among those even self-healing properties for semiconducting thin films.

The study of biology, from single cells and tissues to complex organisms, has led to many new ideas in science and technology. Engineered biomimicry, comprising bioreplication, bioimitation, and bioinspiration, takes concepts, learns from nature, and applies them in different fields of science and technologies, ranging from new materials and novel devices to complex systems and processes. Eco-manufacturing is essential for humanity to achieve social, environmental, and economic sustainability. Materials and energy are the two most critical manufacturing cost factors, accounting for the most pressing environmental impacts in their extraction, processing, and use. In nature, biological systems produce structures using materials and energy from the surrounding environment. Perhaps the simplest case is plants' production of O2 from CO2 through photosynthesis. More complex natural production resulting in direct market value includes wood production by trees and silk by silkworms. This talk will focus on transforming molecules via bio-inspired processes into bio-inspired materials, devices, and structures at the industrial scale.

Intelligence, understood as cognitive process, can be described both through a symbolic approach, which couples itself well with the adoption of technological elements such as the digital world, and through a continuum approach, more familiar with biology. Current experiments performed with functional liquids will be discussed, with a reference to holonomic machines and to the achievement of liquid state analogue memories, artificial neural networks and reservoir computers, where the continuum approach is more appropriate. Recent results about the first liquid state, electrically programmable, in memory computing system will be discussed, highlighting novelties, opportunities and drawbacks of using liquid reservoirs for calculus. In particular their massively parallel structure, resilience towards fluid loss, electrostatic discharges and mechanical vibrations, and most importantly their infinite endurance suggest several advantages. Pavlovian learning in colloids and related effects will also be discussed.

Researchers conventionally employ thermal imaging to monitor the health of animals, observe their habitat utilization, and track their activity patterns. These non-invasive methods can generate detailed images and offer valuable insights into behavior, movements, and environmental interactions. The aye-aye (Daubentonia madagascariensis), an endangered lemur from Madagascar, possesses a uniquely slender third finger evolved for tapping surfaces at relatively high frequencies. The adaptation enables acoustic-based sensing to locate cavities with prey in trees to enhance their foraging abilities. The authors’ previous studies have demonstrated some descent simulating dynamic models of the aye-aye’s third digit referenced from limited data collected with monocular cameras, which can be challenging due to noisy and distorted images, impacting motion analysis adversely. In this proposed research, high-speed thermal cameras are employed to capture detailed finger position and orientation, providing a clearer understanding of the overall dynamic range. The improved biomimetic model aims to enhance tap-testing strategies in nondestructive evaluation for various inspection applications.

This study presents a biomimetic approach for developing scalable 3D printable models of a California sea lion pelvis using DICOM images derived from CT and MRI scans. The images were processed using Simpleware ScanIP software to create accurate and detailed representations of the targeted anatomy. The resulting models were then modified and optimized for 3D printing. The motivation behind this research is to provide a realistic and cost-effective alternative to traditional training methods for veterinary blood collection. The proposed work has the potential to enhance veterinary education and training, improving the quality of care provided to animal patients

The paper explores the potential of Silver-based Self-Directed-Channel (S-SDC) memristors as a solution for artificial synapses in energy-efficient biologically-inspired computing. These memristors offer programmable resistance modulation for neural network circuits, addressing current AI hardware challenges like the von-Neumann bottleneck. The research delves into S-SDC memristors, analyzing their conductivity manipulation via silver cation migration. It investigates conducting states and temporal fluctuations, revealing a range of conductance states inherent to S-SDC memristors. Enhanced programmability is highlighted in lower conductivity states, aiding controlled resistance adjustment. The study also quantifies the impact of migration-induced fluctuations on device reliability. In summary, the paper establishes the potential integration of S-SDC memristors into efficient neuromorphic computing architectures, harmonizing computational demands and energy sustainability. It emphasizes the memristors' unique attributes—conductivity control, programmability, and stability—for advancing neuromorphic computing.

In nature, nanopores are often responsible for broadband light scattering phenomena. For example, some snakes develop white, reflecting ventral scales to avoid overheating caused by highly radiative soil and rocks. Female Carpenter Bees (Xylocopa caerulea) are covered with blue hairs on their head, thorax, and parts of the abdomen serving for intraspecific recognition. We report on the optical properties of nanopores, resulting in structural whiteness in snake ventral scales and vivid blue hues in Carpenter bees due to both pigmentary and structural color. In my presentation, I review our recent studies on natural broadband reflecting structures reflecting light due to nanopores.

Scientific and technological advances have a profound impact on the defense capabilities of worldwide nations. These advances were relatively slow at the beginning of the Industrial Revolution, but dramatically increased in the 20th century. In this line, biomimetics, a field of constant growth and relevance within the technoscientific community, has the potential create a remarkable impact in the broad fields of security and defense. Some applications of biomimetics, a discipline which can generate novel approaches to address both current and future challenges in these fields, will be suggested.

Single-shade dental resin composites with the 'chameleon effect' closely match the tooth's optical spectrum, enhancing color blending. Structural color, based on light interference, contributes to this effect. The study investigates submicron filler particles' impact on optical properties and the chameleon effect. Four single-shade composite materials were investigated. Their surface was imaged in a scanning electron microscope. Light transmission through the materials for wavelengths between 200 and 800 nm was measured using a spectrophotometer. Three-dimensional nanotomography data were obtained through transmission X-ray microscopy at the ANATOMIX beamline, Synchrotron SOLEIL, France in both absorption and Zernike phase contrast modes. This revealed the differences in the microscopic structure of the four materials, both in shape and size distribution of the filler. Remarkably, the chameleon effect appears for all the materials despite their structural differences.