This PDF file contains the front matter associated with SPIE Proceedings Volume 12944, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

Urban overheating is a widely recognized consequence of human activities that contribute to climate change at the urban scale. This phenomenon has devastating effects, including increased energy demand for cooling, heightened air pollution, and associated health risks, particularly during heat waves and in energy-poor conditions. Consequently, cities worldwide are implementing strategic measures to mitigate and adapt to these urban heat islands. One effective approach to mitigation involves the use of cool materials, which possess the ability to reflect or re-emit thermal radiation due to various factors. Daytime radiative cooling is a specific application of cool materials that has the potential to achieve sub-ambient surface temperatures, making it suitable for urban surfaces such as roofs, facades, and streets. Despite the acknowledged potential of radiative cooling, there is a lack of detailed, replicable experimental protocols and numerical assessments in the existing literature. This gap can be addressed by adapting the Solar Reflectance Index (SRI), a crucial metric for quantifying this potential, and further enhancing its capabilities. In order to advance our understanding and application of radiative cooling, it is imperative to develop a comprehensive experimental protocol and conduct thorough numerical assessments. By doing so, we can unlock the full potential of cool materials and their ability to combat urban overheating. This research will contribute to the ongoing efforts to create sustainable and resilient cities that are better equipped to tackle the challenges posed by climate change.

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 this study, 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 actuator as legs and adopted a bounding gait for the locomotion. A tendon-driven actuation method was utilized for the movement of the origami actuators. The origami actuators were controlled via predefined operation signals for the bounding gait. An operating condition is 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.

An understanding of avian flight stability suggests a new approach to morphing aircraft design. Specifically, studies of avian species reveal that they 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 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 and track changes inertia and how that effects the roll rate using a simple decoupled roll rate expression. Asymmetric wing sweep can be used to effect advantageous roll maneuvers for highly agile flight. Essentially with one wing swept, the mass moment of inertial decreases causing a large roll velocity, desirable to initiate a fast turn.

This research work focuses on the development of a dynamic flapping wing actuation mechanism for bat-like micro drone, based on Shape Memory Alloy (SMA) wires combined with compliant beam joints. The SMA wires' unique properties enable the robot to achieve wing flapping, mimicking movements of natural bat wings, with almost zero cost in terms of weight and occupied volume. The idea is to implement SMAs in an agonist-antagonist muscle-like configuration, paired with compliant beam joints at the shoulders of the wings, exploiting the resonance frequency of the beam and wing inertia. The study utilizes 50 micrometer diameter SMA wires strategically integrated into the bat structure, which has a total weight (considering body, actuators, and electronics besides power supply) of approximately 20 grams. The results demonstrate that the drone can achieve a substantial wing-span flapping amplitude of 80° at a frequency of 5 Hz without the need for any external cooling systems. This achievement is particularly significant given the well-known limitations of SMAs in high-frequency actuation tasks. By exploiting the resonance of the compliant beam joint, designed to have a specific natural frequency, the drone also features improved energy efficiency at the designated flapping speeds, comparing to a normal hinge joint. In conclusion, the research showcases the large potential of SMA micro-wires in enhancing performance and characteristics of robotic bio-inspired systems, particularly when combined with mechanical structures which can help overcome its limits. The achievement opens doors to significant improvements in the field of flying biomimetic micro-structures, promising exciting possibilities for future applications in surveillance, exploration, and environmental monitoring.

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 feather vibrations. The 3D printed feather transducers are characterized through vibration testing and wind tunnel testing, and are finally integrated into dried, spread wings for aerodynamic force and vibration sensing of the entire wing. Therefore, the 3D printed feather transducers can potentially be used on future MAVs to improve aerodynamic efficiency and allow fly-by-feel sensing.

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.

Chronic wounds pose a substantial global health challenge, further complicated by the presence of biofilms, which are pathogenic bacterial colonies protected by a biopolymer matrix. These biofilms are notably resistant to both traditional antibiotics and host immune responses, underscoring the critical demand for innovative therapeutic strategies. Among such advancements, transdermal drug delivery mechanisms, particularly microneedle patches, have shown promise in addressing biofilm-related infections effectively. This research introduces a drug delivery system incorporating a piezoelectric transducer (PZT) with a strategically arranged array of drug-infused microneedles. The activation of this system through voltage application to the transducer generates ultrasound waves, facilitating the targeted dispersion of drugs through the creation of localized acoustic fields and fluid streaming. This study delves into the optimization of ultrasound parameters and the mechanics of acoustically assisted drug distribution, identifying the conditions under which ultrasound waves can enhance the transfer of therapeutic agents via microneedles. It distinguishes between resonant and non-resonant frequencies, which influence the pattern and efficiency of drug diffusion into biofilms. The analysis extends to the simulation of drug penetration into biofilms, offering insights into concentration profiles at various depths. This investigation not only highlights the potential of ultrasound-enhanced drug delivery for precision medicine but also suggests its applicability in treating a wide array of medical conditions. The ability to precisely control drug delivery, coupled with real-time monitoring, signifies a transformative approach to medical treatment, with the potential to significantly improve patient outcomes and quality of life.

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.

Nature’s exquisite designs are a constant source of inspiration for materials scientists, yet our ability to replicate biological interactions in engineered systems is often limited. Biological systems exist in perfectly balanced environmental conditions that regulate their functionality. A major obstacle in exploiting biological interactions in macroscale materials is a lack of understanding of how environmental changes, including scaling, affect the intrinsic molecular functionality of the biological unit, ultimately impacting macroscale behaviour. This paper explores our approach to understanding complex behaviours across multiple length scales and how we use this information to rationally design protein cross–linked hydrogels.

Optical diffusers serve to a variety of applications by spreading incident light over a wide angular range. In general, the ideal conditions of the optical diffuser are to simultaneously satisfy high transmittance, wide angular spread, and low color dispersion. However, in the conventional diffusers based on scattering or refraction, the above conditions fall into tradeoff relationship, which make realization a challenge. Inspired by the specific color of Morpho butterflies that give simultaneously high reflectance, wide angular spread, and low color dispersion, we have recently proposed a design of new diffuser that satisfies the ideal conditions. However, our original design was difficult to fabricate because of its high aspect ratio at nanoscale. Then, we designed a new Morpho-type diffuser having double-step structures with disordered height for the feasible fabrication. The design was verified by numerical simulations, and the structural parameters were optimized. Finally, the optimal design was proposed with ideal optical properties, which is feasible to fabrication.

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), a rare and 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 paper examines the capabilities of Silver-based Self-Directed-Channel (S-SDC) memristors as artificial synapses in energy-efficient and biologically-inspired computing systems. These memristors stand out for their programmable resistance modulation, which is crucial for neural network circuits and addresses key challenges in AI hardware, such as the von Neumann bottleneck. The research focuses on the conductivity manipulation in S-SDC memristors through silver cation migration, exploring various conducting states and their temporal fluctuations. This analysis uncovers a spectrum of conductance states unique to S-SDC memristors, with enhanced programmability particularly evident in lower conductivity states, facilitating precise resistance adjustments. Additionally, the study assesses the influence of migration-induced fluctuations on the overall reliability of these devices. The paper advocates for integrating S-SDC memristors into neuromorphic computing architectures, highlighting their ability to balance computational efficiency with energy sustainability. The memristors' distinct features, including controllable conductivity, adaptability in programming, and stability, are underscored as key contributors to the evolution of neuromorphic computing.

Caries affects billions of individuals worldwide, thus pointing out the importance of advancements in restorative dentistry. Dental resin composites yield restorations with satisfying mechanical properties, therefore the focus of development has shifted to accelerated treatments and esthetic aspects. Challenges in matching tooth color arise due to limited options, application changes, and color variations over time. Single-shade composites with the 'chameleon effect' adapt their color to the surrounding enamel by closely matching the tooth's optical spectrum, enhancing color blending. Structural color, based on light interference, contributes to this effect. The study investigates the submicron filler particles' impact on optical properties and the chameleon effect. Four single-shade dental resin composite materials were investigated. Needle-like samples about 100 μm in diameter were prepared and imaged in a scanning electron microscope. Light transmission through the materials for wavelengths between 200 and 900 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 mode with 23 nm voxel size. The real space information was complemented with small-angle X-ray scattering. These experiments revealed substantial differences in the microscopic structure of the materials. In the case of Omnichroma, the filler consists of almost identical spheres with a diameter of 260 nm while Filtek Universal exhibits polydisperse, irregularly shaped fillers. Additionally, Venus Pearl One’s fillers have a polyhedral shape and a wide size distribution. Finally, the setups used did not reveal any clearly identified microstructure of the Chroma Fill composite. Although all investigated materials are known to exhibit the chameleon effect, their differences in micro- and nanostructure call into question previous hypotheses on the chameleon effect’s origin from structural color. While we have now a reasonable understanding of filler morphology, size distribution and spatial arrangement, more information is needed on the exact chemical composition of filler and matrix and their interaction with electromagnetic waves, including possible nonlinear effects.