This PDF file contains the front matter associated with SPIE Proceedings Volume 12481, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

The bioworld is an immense repository of successful solutions to overcome diverse problems. This repository can be used for biologically inspired design (BID). In this lecture, I point out various aspects of BID, including (i) identification of bioworld systems of relevance for engineering, with emphasis on multifunctionality, multicontrollability, sustainability, and circular economy; (ii) correlation of engineering problems with solution strategies available in the bioworld; and (iii) descriptions of two pathways for systematic adaptation of bioworld solutions to solve engineering problems.

Soft materials are attractive to engineers due to their low density, ability to sustain large deformations and customization of properties. These custom properties are realized by tailoring the microstructural architecture and optimizing the constituent materials. However, achieving complex behavior at the macroscale is difficult through conventional engineering top-down approaches. Instead, we draw inspiration from a more biological bottom-up approach based on the concept of emergence. Slime molds and fungi are fascinating models for emergence; formed by aggregation of almost identical cells, their internal networks optimize transport better than engineers, solve mazes, detect masses at a distance, or memorize periodic events. We establish here a theoretical and computational framework to explain, quantify and reproduce how this feedback between macroscopic features and local tuning of mechanical properties determines an emergent coordinated response of the network morphology. These networks have the ability to grow, survive, or die in the presence of different concentrations of nutrients and to redistribute them, thus optimizing their proliferation. We propose a phase-field scalar variable to represent the network matrix evolution and a diffusive-advective process for nutrient distribution. This framework enables high-fidelity simulations of slime molds in three-dimensional space, which are challenging due to the coupled physics involved, high-order partial differential equations, and the existence of a highly complex evolving geometry. The emergent properties of these organisms are similar in nature to tissues with transport networks, and we can exploit them to design self-healing materials, fungal sustainable building elements, or even coordinate drone swarms. This investigation is a road to the microstructural design of active soft matter, an object of interest in many fields of engineering and science.

This paper explores how Biologically Inspired Design (BID) can be applied in the development of medical devices through a concrete case study. Nature has been developing, over the last 3.8 billion years, the most efficient mechanisms to fulfil a function and overcome challenges. Based on this giant innovation database, BID has received an exponential increase of interest since the 1950s and has led to innovative solutions in a vast variety of fields. The present study is motivated by a medical device which should be designed for insertion in a cavity, followed by a significant expansion inside the cavity. Once expanded, the device should be able to radiate light for disinfection purposes, while simultaneously allowing air replacement in the cavity. Finally, the device should contract to its original size before being extracted from the cavity. In order to propose radically new ideas for designing such a device, BID is applied to a range of functions namely i) how to expand an object after insertion in a cavity, ii) how to promote air circulation in the cavity, iii) how to radiate light to all surfaces in the cavity and finally iv) how to contract the object again. This paper presents and discusses the BID process as well as the outcomes of this study. 25 biological strategies have been identified throughout the project, 7 ideas were generated and 4 more detailed concepts and physical mock-ups emerged from these ideas. 2 of them were considered interesting for further development, which indicates a good efficacy of the process. The whole study lasted 32 working days, suggesting a high efficiency of the BID process.

The preliminary focus of this research is to produce and characterize an active transparent silk material that can autonomously fold from a 2D film to a final 3D geometry while also abiding by biomedical engineering principles. Silk is a natural protein polymer consisting of amino acids that contribute to its higher hierarchical protein structures. The most common of these structures present are amorphous random coils that are more hydrophilic and stacked β-Sheet crystalline regions that are more hydrophobic. The transparent regenerated protein film is a water responsive (WR) material that can expand or contract in response to changes in relative humidity (RH). This was accomplished by tuning silks crystallinity by increasing the solutions degradation period. This research is highly valuable for self-folding materials such as soft robotics for biomedical and optical applications, and also contributes a framework constrained by sustainability and green engineering.

Snakes optimize their body scales in terms of locomotion, thermoregulation, and conspicuousness for survival in their respective ecological niche. Here, we present our analysis of the scales of the Hungarian Meadow Viper (Vipera ursinii rakosiensis). Micro-fibril structures with nano-scale steps are observed on the ventral scales. These structures are oriented from head to the tail direction. Interestingly, a ridge like reticulate structure is observed on the dorsal scales. Spectacle scales are mostly flat and have polygonal cracks on the surface. High optical transmittance is measured on the ventral and spectacle scales. However, much reduced transmission is recorded on the dark dorsal scales which can be attributed to the presence of melanin within the scales. The scales are water hydrophobic; however, the contact angles are not high enough to allow for self-cleaning properties.

Twisted and coiled string (TCS) artificial muscles are recently discovered motor-driven compliant actuators that can consistently generate up to 70% strains. The TCS muscles’ actuation is realized in two sequential phases, namely, twisting and coiling. Actuation in the twisting phase results in smooth linear contraction along the TCS muscles’ length. This behavior is identical to that of the popular twisted string actuators. In the coiling phase, the TCS muscles are overtwisted to form coils that generate large and unique non-smooth contraction of strings. The coiling phase in actuation cycle is underexplored and exhibits unique characteristics: Firstly, at a constant motor speed, twisting of strings generates drastic contraction accompanying larger non-smooth actuation during coil formation as compared to the intermittence between adjacent coil formations. Secondly, evident hysteresis appears during the coiling-induced actuation, likely due to large friction between strings when coiled. Lastly, the muscles actuation transition between twisting to coiling is intricate and largely uninvestigated, especially when they operate under different loading conditions and different motor twisting inputs. In this study, a comprehensive experimental characterization of the coiling-based actuation of the TCS muscles is conducted. Firstly, the load dependence of the TCS muscles’ behavior is examined by applying input cycles under different loading conditions. Secondly, the non-smooth behavior is investigated by using sequences of input motor turns with different frequencies. Lastly, the hysteretic behavior and the properties of transitioning conditions are examined by applying different ranges of the input cycles under different loading conditions. The results serve as a basis for future studies on modeling and control of the TCS muscles’ coiling-based actuation.

Pneumatic artificial muscles (PAMs) consist of an elastomeric bladder wrapped in a Kevlar braid. When inflated, PAMs expand radially and contract axially, producing large axial forces. PAMs are often utilized for their high specific work and specific power, as well as their ability to produce large axial displacements. Although the axial behavior of PAMs is well understood, the radial behavior has remained under-utilized and is poorly understood. Radial expansion in large diameter (over 2 inches) PAMs has recently been used in worm-like robots to create anchoring forces that allow for a peristaltic wave which creates locomotion through acrylic pipes. By radially expanding, the PAM presses itself into the pipe, creating an anchor point. The previously anchored PAM then deflates, which propels the robot forward. Modeling of the radial expansion forces and anchoring was desired to determine the pressurization required for proper anchoring before slipping occurs due to the combined robot and payload weight. Modeling was performed using a force balance approach to capture the effects that bladder strain and applied axial load has on the anchoring force. Radial expansion testing was performed to validate the model. Force due to anchoring was recorded using force transducers attached to sections of acrylic pipe using an MTS servo-hydraulic testing machine. Data from the test was compared to the predicted anchoring force.

Some species of birds are known to whiffle, or fly inverted, in order to rapidly lose altitude, move laterally, or respond to gusts and atmospheric disturbances. Recently, gaps inspired by the bio-mechanics of whiffling have been found to change the forces and moments of an uncrewed aerial vehicle (UAV) wing. These novel gapped wings have been studied in terms of rapid descent and roll control. However, their potential as gust alleviation devices and overall impact on aircraft dynamics remained unknown. Here, we analytically determined the trim state, free response, and gust response of aircraft with varying gapped wings. The gaps shifted the aerodynamic center of the wing forward but in general beneficially decreased the wing’s overall contribution to the aircraft pitching moment. This effect resulted in a steeper glide angle and higher velocity at trim. The gaps also reduced the phugoid mode by decreasing its natural frequency and increasing damping. However, all of the aircraft could require a controller for the short period mode due to a higher natural frequency. Finally, we showed that the gapped wings improved the aircrafts’ response to transverse and streamwise gusts by increasing damping and reducing the maximum amplitude of oscillations. Despite some practical design challenges associated with the gapped wings, they ultimately benefited the aircraft’s dynamic response and effectively mitigated gusts. Thus, the gapped wings could be a suitable control surface for gust alleviation.

The phenomenon of fish schooling - coordinated swimming of fish in polarized groups of specific spatial formations - is commonly observed in several species of fish. Fish schooling may even provide hydrodynamic advantages reducing the overall swimming cost of the group. To date, the role of hydrodynamics in coordinated swimming is not completely understood as it is difficult to separately study the role of hydrodynamic interaction from other forms of interaction between the fish. Here, we propose a statistical methodology based on information theoretic tools and flow velocity measurements, that can potentially tease out the hydrodynamic interaction pathways from visual and tactile ones. To avoid experimental confounds from bidirectional interactions and objectively understand cause-and-effect relationships, we design a robotic platform that mimics the behavior of two fish swimming in-line in a controlled setup inside a water channel. We examine the response of a flag to the fish-like unsteady wake generated by an actively pitching airfoil located upstream. We systematically quantify the passive hydrodynamic effect by studying the flapping motion of the flag located downstream of the airfoil in response to both periodic pitching and less predictable, random startling motion of the upstream airfoil. The study integrates experimental biomimetics with information theory to establish a deeper understanding of hydrodynamics in fish schooling.

The advantage of structurally colored materials is their stability and the fact that they can be sourced sustainably. In addition to the challenges of producing high-quality colors, fabrication and patterning are also important issues. Different printing processes are available depending on the area of application. In this paper, we report on recent advances in the fabrication of structurally disordered photonic materials by patterning self-assembled color pigments using inkjet printing and by direct laser writing.

Optical metasurfaces are inscribed in surface relief on azobenzene molecular glass thin films following double and triple sequential exposures to laser interference patterns with very close periodicities, resulting in two-fold and three-fold hierarchical Moiré gratings respectively. These metasurfaces formed due to the unique photomechanical effect in azobenzene materials, in which molecules migrate from zones of high to low laser irradiance. The laser interference patterns were obtained using a Lloyd mirror interferometer and a continuous wave laser having a wavelength of 532 nm and an irradiance of 200 mW/cm². The resulting optical metasurfaces, which resembled surface features of a Peruvian lily flower petal, were characterized using atomic force microscopy, optical microscopy and surface profilometry techniques. It was found that the highly-customizable surface characteristics of the resulting metasurfaces can significantly alter their hydrophobicity.

The most successful Computer Vision (CV) models have been inspired by biological systems, most frequently mammalian neurophysiology. While mammalian vision is exceptional at object recognition and classification, we hypothesize that the emphasis on mammalian bioinspiration underserves some computer vision application domains increasingly critical for intelligent systems, like single-object tracking (SOT) in a non-stationary frame. We propose a framework to identify unique mechanisms of the avian visual system that can then be incorporated into conventional SOT models to test how mimicking avian vision modifies current tracking capability. Avian neurophysiology has evolved mechanisms to ensure successful tracking while in motion. From this framework, three experiments were selected to explore mechanisms tied to tracking and unique to the avian visual system: image filtering (retinal structure), motion discrimination and saliency (Tectofugal Pathway), and image unification (Centrifugal Pathway). For each experiment, we also utilize different bioinspiration approaches. For the retina, an existing eagle-eye-based adaptation mechanism was applied and specific scenarios were observed where this prevents tracking loss. For the Tectofugal Pathway, a spiking neural network was developed based on the pigeon nucleus rotundus that was able to identify salient objects better than a metric-based method. For the Centrifugal Pathway, a recurrent modification to a convolutional neural network based Event+RGB tracker was proposed that had better initial accuracy. These results show improvements in specific cases and pave the way for more detailed analysis. The resulting framework has the potential to evaluate bio-inspired modifications to computer vision pipelines.

Steel is employed almost everywhere, including biomedical devices and surgical tools, domestic and industrial equipment, and transportation. However, steel is prone to deterioration during contact with water which leads to biofouling and corrosion, resulting in degradation in durability and function ability. Inspiration from nature, such as lotus leaves, is getting more attention to fabricating water-repellent superhydrophobic coatings on steel surfaces to solve aforesaid problems. In this present study, superhydrophobicity on steel surfaces was achieved by a two-step process: copper coating on the steel substrate via an environmentally friendly and time-efficient electrodeposition method, followed by immersion of copper-coated steel in long-alkyl chain solution. The wettability was measured through the water contact angle using the goniometer, which confirmed the achievement of superhydrophobicity. To demonstrate the application of this coating in a corrosive environment, a considerable reduction has been observed on the superhydrophobic surface.

This paper presents the design and construction of a biomimetic swimming robot inspired by the locomotion of rays. These fishes move by flapping their pectoral fins and creating a wave that moves in the opposite direction to the direction of motion, pushing the water back and giving the fish a propulsive force due to momentum conservation. While this motion is similar to other fishes in terms of efficiency, it gives better maneuverability and agility in turning. The robot's fins are molded from silicone rubber and moved by servo motors driving mechanisms inside the leading edge of each fin. The traveling wave, mimicking the movement of the fin, is passively generated by the flexibility of the material. The robot is also equipped with a tail that acts as a rudder, helpful in performing maneuvers and maintaining the desired attitude. The rigid central body of the robot is the housing for motors, electronics, and batteries. Sensors embedded in the robot allow to estimate its behavior, to compare different swimming strategies, and evaluate the best algorithm to control the robot.

Langmuir-Blodgett troughs provide an excellent system to deposit monolayer films onto flat and curved substrates. However, most trough designs use motorized barriers to compact the film, and it is difficult to fully eliminate the capillary waves and striations on deposited films caused by motorized barriers. Here, we present an inexpensive design for a benchtop LB trough that compresses the film without motorized barriers; instead, it is the trough's geometry that compresses the film in a drainage basin. We demonstrate this approach with a 3D printed drainage basin and with self-assembled polystyrene colloidal films on a range of 3D glass substrates: a jar, a bulb, and a compressor tube. We provide a mathematical formalism to coat 3D objects with arbitrary size and shape; especially with facile 3D printing, this concept may be extended in a cheap and modular approach.