This PDF file contains the front matter associated with SPIE Proceedings Volume 11586, including the Title Page, Copyright information, and Table of Contents.

While great advances in medicine has been made in the past century, the overall infrastructure of the healthcare system has not progressed. Patients (who are not feeling well) are still expected to travel to a centralized location for discrete, reactionary-based care where the healthcare provider only has a brief window to assess the patient’s health. Unless the symptoms are overt at the time of examination, the subjective evaluation relies heavily on the self-reporting of symptoms from the patient. This often results in delayed or improper diagnoses. In contrast, we know that physiological signals precede clinical deterioration. We have developed a suite of low-cost, unobtrusive, Band-Aid©-like physiological sensors to continuously monitor patients’ cardiovascular and pulmonary functions. We seek to continuously quantify subtle physiological changes to predict, and eventually prevent, the onset of acute clinical events.

The presentation will discuss some recent research topics in the area of Ultrasonic Testing of materials and structures at UC San Diego. The first topic is the passive extraction of the Green’s function of the test piece subjected to an uncontrolled excitation. This concept is being utilized to detect, at high speed, internal defects in rail tracks using the train wheels as the acoustic excitation. The second topic deals with the nonlinear wave propagation regime and its increased sensitivity to material state awareness compared to the linear regime. Nonlinear wave propagation will be presented for the case of waveguides and the case of constrained solids subjected to thermal excursions. The third topic deals with ultrasonic Synthetic Aperture Focus (SAF) imaging and proposes some techniques to improve image quality in the cases of bulk-wave testing and guided-wave testing. The fourth topic is the identification of the elastic constants of multilayered composites based on the inversion of guided wave dispersion curves and optimization algorithms.

Smart structures systems have evolved tremendously in the last 40 years, enabled by advances in constituent and integrative science and technology. Every significant advance was made by a talented individual who benefitted from collaborations with others offering complementary perspectives. Such interdisciplinary explorations illuminated potential disruptive functionality and exposed issues related to the realization of complicated systems. All aimed at a goal of societal impact: applications and technologies that improve people’s lives while creating businesses and jobs. Some advances have spurred novel products or capabilities, while others languish for a variety of reasons. Examples will illustrate the moves and missteps of this potent smart structures dance.

Digital Fabrication with Concrete (DFC) encompasses 3D Concrete Printing (3DCP) and many other on-site and off-site fabrication methods. DFC is beginning to move from an era of invention and demonstration to one of reality. It has only been 15 years since inception and yet printing offices, houses and bridges are just some of the applications that are being demonstrated at full scale. But this is not all DFC has to offer. Some of the greatest challenges face the production and maintenance of the built environment to deliver continual improvement with less material and ever decreasing skilled labour. Automation of construction manufacturing will be critical if we are to realise Industry 4.0, providing greater productivity while reducing uncertainty and cost. DFC is at the vanguard of this aspiration and this session will take you through the technologies, the achievements and provide the future outlook for these techniques.

Many biological materials such as bone, teeth and nacre exhibit superior mechanical strength and toughness. These materials share similar hierarchical arrangement that stiff blocks are embedded in a soft matrix. For example, the sophisticated brick-and-mortar design in nacres can effectively increase the fracture toughness by a factor of 3,000 compared to its major component – mineral. Although extensive studies have been done attempting to understand the toughening of the nacre-like materials, the underlying mechanisms associated with crack behaviors are not fully clear yet. This study applies the phase-field method for crack behaviors in both layered structure and nacre-like materials to distinguish the importance of the commonly observed toughening mechanisms. First, we investigate the toughening of a simple layered structure, where the surfing boundary condition is imposed to suppress the crack deflection. We compute the maximum energy release rate using the J-integral technique to find out that the effective fracture toughness is much less than the experimentally measured fracture toughness of these bio- composite materials. Then we investigate the crack growth in a nacre-like material to obtain a phase diagram summarizing four different modes of crack growth: straight crack, interface crack, branching, and crack arrest for a range of structural parameters relevant to nacres, including the aspect ratio, volume fraction of mineral, elastic modulus mismatch and fracture resistance mismatch. Our results clarify the relation between the complex hierarchical microstructure and the toughening mechanisms, such as crack bridging, microcracking and tablet sliding.

Formaldehyde (HCHO), a common Volatile Organic Compound (VOC), generated from human activity and industry, is ubiquitous in the indoor and outdoor environments in the Mexico City Metropolitan Area (MCMA). VOCs react with nitrogen oxides (NOx) creating frequent ozone (O₃) events which are hazardous to human and ecosystem health in the MCMA. Research into current indoor VOC removal technologies reveal that indoor/outdoor airflow is not easily mediated, besides, these technologies often lead to secondary, undesirable by-products. We employ the Biomimicry Thinking Methodology, and ask: “How would Nature solve this problem? Research finds that plants send VOCs into the soil where they are largely processed via the microbiome. The composition of the microbiome, the soil, sunlight, water and nutrient availability, wind, barometric pressure, temperature, pH, aeration, plant community, and the concentration and mix of VOCs affect the rate the soil either emits or sinks the compounds. We find research supporting the correlation between native plant-microbiome relationships and microbiome health. Discussion of context considerations specific to the MCMA informs a design concept addressing indoor and outdoor atmospheric HCHO removal. HCHO contributes to O₃ events and can be processed via the microbiome using natural chemical pathways.

Biological cells possess a membrane, which keeps the constituents in the cell, prevents the penetration of unwanted substances, and triggers the transport of nutrients and waste products. Such membranes can confine drugs for the transport to their target and could also be prepared from artificial phospholipids. They are stable in planar and spherical arrangements. Recently, metastable facetted liposomes have been discovered. These liposomes exhibit the specific property that they can release their cargo upon external and internal physical stimuli. Our team has demonstrated that changes in the medically relevant temperature range give rise to structural changes of selected liposomes [Langmuir 35 (2019) 11210]. A more important study [Materials Today BIO 1 (2019) 100003] provides a robust and cutting-edge combination of synchrotron radiation-based small-angle X-ray scattering and microfluidics to investigate the in situ structural modifications and shape deformations of non-spherical liposomes about 100 nm in diameter when flowing in constricted blood vessels, here mimicked by microfluidics channels. This sophisticated approach resulted in real-time data that revealed insights into the intriguing flow-induced behavior of nanometer-sized liposomes. The mean size and shape of the non-spherical, facetted, and relatively stiff liposomes as well as their average bilayer thickness, which could be spatially detected under flow conditions akin to the ones occurring in constricted blood vessels are altered at the entry and the exit of the constrictions in the channels of the microfluidic device. The bilayer thickness increase of the faceted liposomes is explained and convincingly illustrated by the hydrodynamical pressure-gradient, which induced the loss of interdigitation between the phospholipid acyl chains. Therefore, the hydrodynamically induced pressure-gradient force rather than the anticipated wall-shear stress could trigger the structural modifications of nanometer-sized liposomes and the related cargo release at vessel constrictions. Furthermore, analyzing selected flow rates below the maximal values during pulsatile flows in healthy and atherosclerotic blood vessels, the impact of the hydrodynamic stimuli on shape and structure of the non-spherical liposomes was identified.

The soft electroactive polymer material, ionic polymer-metal composite (IPMC), has been used in various applications of soft-robotics for both its sensing and actuating capabilities. When used as a sensor, IPMCs are typically positioned in a rectangular cantilever orientation, where the produced voltage response is indicative of the displacement occurring as the IPMC is bent by an induced force. Upon changing the orientation of the IPMC sensor, alternative reproducible voltage responses occur depending upon which surface the induced force is acting upon. The results of this study can be used to optimize the design of soft-robot devices that use IPMCs as a main sensing component.

We have heavily relied for a few centuries on fossil fuels, which are basically dead plant material that was sequestered and converted millions of years ago, but the rapidly increasing energy demand combined with climatic challenges means we need to develop a large-scale supply of energy from sources without climatic impact. An obvious choice is to use solar energy directly when possible, and a complete global transition to solar energy by 2050 is realistic and cost effective. However, in order to find space for the large areas needed for harvesting solar energy by photovoltaic means, it would be advantageous if solar panels could be incorporated into urban buildings and free land for other uses. We undertook an analysis of the needs and requirements from the building industry that will allow for a more widespread use of solar panels on buildings, also referred to as Building Integrated Photo-Voltaics. Specifications and options for the visual incorporation of the solar panels in the building envelope were identified. Special attention was paid to (i) the role of modularization and standardization in architecture and (ii) the role of color and reflectance. A standardized mounting system is proposed that will allow for modular attachment of solar panels, making it easy to adjust, repair, and replace individual panels. Biological inspiration can be used to improve the system further. The forced-air ventilation of the tunnels of prairie dogs shows how to enhance cooling. The non-iridescent wings of butterflies of the Morpho genus, proposes how a low-cost structurally colored film can be inserted into the solar panel during its assembly.

This work highlights a novel method to prepare conformal ultrathin films of chitin and hybrid chitin-based biomaterials from the gas phase by Molecular Layer Deposition (MLD) technique. MLD is a thin film grow technique, where the structure is built through sequential self-terminating gas–solid reactions. As precursors for both MLD process we are using the sugar-type molecule N-acetyl-D-mannosamine (ManNAc) and coupling it with the surface using thionyl chloride vapors and Trimethylaluminum (TMA) for chitin and alumochitin MLD consequently. ATR-FTIR, X-ray photoelectron spectroscopy (XPS) and Solid-state NMR (ssNMR), High resolution TEM (HRTEM) and Energy dispersive X-Ray spectroscopy (EDXS) analysis were performed to examine the obtained MLD films. The MLD nature of the growth of the films obtained using TMA and ManNAc was examined in situ by quartz crystal microbalance (QCM) experiments.

Deposition of thin functional films by atomic layer deposition (ALD) is commonly applied to inorganic substrates in order to add or modify their functionalities dominantly in application fields such as electronics, photovoltaics or energy storage. However, the potential of ALD goes far beyond those application fields and numerous new applications that involve thin films produced by this technology are emerging. A very interesting research and development direction involves biomaterials. Herein, various individual directions can be distinguished, namely i) material development based on blends of biomaterials and inorganics, ii) development of biocompatible thin films coatings for medial implants, or iii) approaches towards controlled drug delivery. Besides the main positive characteristics of ALD that include extreme control over the coating thicknesses, thickness uniformity and conformality, one key aspect of such processing is the fact that many materials can be deposited at substantially lower temperatures than with competing technologies. This allows for processing of some thermally sensitive materials such as biomaterials or polymers, still maintaining the high quality of the final coating. As a result, functionalization of polymeric implants in a simple and cost-effective way is foreseen. Although the research in those areas is still in its infancy, the acquired knowledge about suitable processes and materials promises great new developments in near future. This talk will give an overview of the current publicly known research that relates to biomaterials and biocompatibility of coatings and will discuss some future perspectives of ALD in this respect.

We have designed multicontrollable and multifunctional metasurfaces comprising pixelated meta-atoms. Optimal tricontrollable metasurfaces comprising graphene-patched pixels for electrical control and InSb-patched pixels for thermal and magnetic control were designed to function either as terahertz absorbers or terahertz stopband filters. Clearly, these devices can also serve as trifunctional sensors. A single-pixel graphene-sandwich meta- atom was designed to function as a reciprocal switch, a stopband, a frequency shifter, and an isolator for the terahertz spectral regime. Such multicontrollable and multifunctional metasurfaces could be incorporated in diverse products, thereby reducing inventory costs, enhancing repairability and product lifetimes, and promoting standardization.

Biological matter may change shape via water absorption or loss. For example, brain tissue shows non-uniform shrinkage during formalin fixation and paraffin embedding, which is the most common tissue preparation for conventional histological analysis. Local deformations can be analyzed with non-rigid registration of non-destructive three-dimensional imaging datasets. We utilized synchrotron radiation microtomography at the ANATOMIX beamline of Synchrotron SOLEIL to image a mouse brain with 3 micron voxel length after formalin fixation, immersion in ascending alcohol series and xylene, and after paraffin embedding. We created a pipeline for non- rigid registration to align the volumes and extract volumetric strain fields. In this way, we could visualize the swelling/shrinkage of anatomical features. This method avoids time-consuming segmentation of brain regions, however it is sensitive to the registration parameters. In this proceedings paper, we discuss the selection of registration parameters in order to generate plausible volumetric strain fields. This protocol can be deployed to any type of shape change of biological matter and allows for the quantification of the related processes.

Successful tomographic imaging of soft tissues with micrometer resolution includes preparation, acquisition, re- construction, and data evaluation. Tissue preparation is essential for hard X-ray microtomography, because staining- and embedding materials can substantially alter the biological tissue post mortem. We performed to- mographic imaging of zebrafish embryos in alcohol and after paraffin embedding with a conventional X-ray source and at a synchrotron radiation facility. The resulting multi-modal, three-dimensional data were registered for direct comparison. Single-cell precision was reached for the synchrotron radiation-based approach, which allows for segmentation of full organs such as the embryonic kidneys. While this approach offers an order of magnitude higher spatial resolution, many of the anatomical features can be readily recognized with the more accessible laboratory system. Propagation-based data acquisition enabled us to demonstrate the complementary nature of the edge-enhanced absorption contrast- and the phase contrast-based modality for visualizing multiple microanatomical features. While ethanol and paraffin embeddings allowed for identification of the same anatomical structures, paraffin-embedding, however, led to more artefacts and shrinkage. The presented multi-modal imaging approaches can be further extended to visualize three to four orders of magnitude larger volumes such as adult zebrafish or complete organs of larger animals such as mouse brains. Going towards even larger volumes, such as the human brain, presents further challenges related to paraffin embedding, data acquisition and handling of the peta-byte scale data volumes. This study provided a multi-modal imaging strategy by the combination of X-ray sources and sample embeddings which can play a role in addressing these challenges.

Aquatic swimming has fascinated researchers for more than a century. In this keynote talk, different types of swimming, their mechanisms of propulsion, and major findings from simulations are reviewed. The body undulations of the fish, which can be approximated well by a backward traveling wave, tend to keep the flow attached on the body of the swimmer. These observations have inspired us to use low-amplitude, backward traveling waves (which can be generated through piezoelectric actuators) for flow control. Our results indicate that backward traveling waves perform better than other types of surface morphing, e.g., standing waves, to control the flow separation over an airfoil.

This paper investigates the effect of resistive forces that arise in compressed fluidic artificial muscles (FAMs) within a variable recruitment bundle. Much like our skeletal muscle organs that selectively recruit different number of motor fibers depending on the load demand, a variable recruitment FAM bundle adaptively activates the minimum number of motor units (MUs) to increase its overall efficiency. A variable recruitment bundle may operate in different recruitment states (RSs) during which only a subset of the FAMs within a bundle are activated. In such cases, a difference in strain occurs between active FAMs and inactive/low-pressure FAMs. This strain difference results in the compression of inactive/lowpressure FAMs causing them to exert a resistive force opposing the force output of active FAMs. This paper presents experimental measurements for a FAM for both tensile and compressive regions. The data is used to simulate the overall force-strain space of a variable recruitment bundle for when resistive force effects are neglected and when they are included. Counterintuitively, an initial decrease in bundle free strain is observed when a transition to a higher RS is made due to the presence of resistive forces. We call this phenomenon the free strain gradient reversal of a variable recruitment bundle. The paper is concluded with a discussion of the implications of this phenomenon.

Exoskeletons, such as scales on fishes and snakes were a critical evolutionary adaptation. Honed by millions of years of evolutionary pressures, they are inherently lightweight and yet multifunctional, aiding in protection, locomotion and optical camouflaging. This makes them an attractive candidate for biomimicry to produce high performance multifunctional materials with applications to soft robotics, wearables, energy efficient smart skins and on-demand tunable materials. Canonically speaking, biomimetic samples can be fabricating by partially embedding stiffer plate like segments on softer substrates to create a bi-material system, with overlapping scales. Recent investigations on their mechanics have shown that the origins of many of these behaviors are not merely due to load distribution but because of an intricate interplay of deformation, sliding and interfacial behavior. Such interplay give rise to property combinations that are typically not visible in the parent material of either the scales or the substrates. Here we review and present the origins of some of their fascinating behavior which include nonlinear and directional strain stiffening in both bending and twisting, dual nature of friction which combines both resistance as well as adding stiffness to motion, emergent viscosity in dynamic loading, and non-Hertzian contact mechanics. We will provide derivation of simple mathematical laws that govern structure- property relationships that can help guide design. We will also demonstrate possibilities in non-mechanical properties such as elementary structural coloration and topography influenced mass deposition. We conclude by providing perspectives of future development and challenges.

In this paper, we designed a quadruped, dog-like robot which has 3 degrees of freedom (DOFs) per leg, and combined two commonly used methods for robot’s gait control, to make better gait planning strategy in different environments. First, we chose the inverse kinematics control method, and established the quadruped robot simulation motion model in Webots to verify the validity of the motion modes such as forward, backward, turning, and height adjustment of the body. Then we utilized the CPG (Central Pattern Generator) control method, and an improved Hopf nonlinear harmonic oscillator, which requires less parameters, smaller computation complexity, and clearer physical meaning, to generate a faster trot gait. According to the timing diagram of different gaits, the coupling topology structure between CPG units was designed, with joint motion curve generated. The simulation and experiment show that compared to inverse kinematics, CPG is more suitable for producing simpler and faster periodic gait planning signals, while inverse kinematics method takes advantages in the body’s self-balance and foot’s adaptation on the ground. The two methods can be complementary to the motion control of the quadruped robot.

We present shape memory alloy (SMA) driven caudal fin soft robotic fish propulsion system. The goal of the project is to build a bio-inspired, soft robotic underwater vehicle that swims and maneuvers quietly and efficiently, much like a real biological fish, without using traditional mechanical motors that produce noise. The vehicle is modeled (shape, size, and mechanics of motion) after the Wahoo fish (Acanthocybium solandri) which can swim efficiently at a high speed. The vehicle’s propulsion thrust is produced by the undulating motion of the back half of the body that produces wave-like motions when actuated. The propulsion is achieved by actuating coiled SMA elements that span successive cross section ribs, on the port and starboard sides, of the vehicle that are designed to pivot at the midpoint of the vehicle. All successive ribs are connected at the midpoint by linkages mimicking the vertebra in a fish, which allow each rib to pivot at the end of the link to which it is attached. Alternating the actuation (turning the current on and off) of the SMA elements on the port and starboard sides produces the desired undulating motion, currently at a frequency of 0.5Hz. The alternate actuation scheme allows the SMA elements to cool down before the next actuation sequence. The thrust produced were measured by mounting the propulsor on a 3-axis load cell in a water tank and recording the force generated at various power levels applied to the SMA actuators. The thrust increases as the power supplied to the actuators were increased. Computational Fluid Dynamics (CFD) simulation is then used to estimate the achievable speed for the full vehicle model at a given thrust level. Inversely, the CFD model is then used to predict the required thrust/force level to achieve the desired vehicle speed. Building upon some preliminary results, we are working on optimizing the kinematic designs, actuator configurations and strategies to achieve higher undulating frequency and thrust to develop a soft robotic fish that can achieve high speed.

Zebrafish is a popular animal model for behavioral, neurological, and pharmacological studies. Particularly enticing is the possibility of studying the underpinnings of social behavior through hypotheses-driven experiments where we systematically intervene on key experimental variables. Robots offer an ideal avenue for performing such experimental manipulations, by affording the creation of highly-controlled, versatile, and customizable stimuli. Within this domain of investigation, we explore the possibility of using robots to “teleport” zebrafish from a tank to the other. More concretely, we propose the development of inanimate robots that allow remotely- located zebrafish to interact with each other in real time by mirroring movement of live fish. Each of the systems consists of a two-dimensional robotic platform, a magnetically- connected replica, a circular tank, and an overhead camera. A real-time tracking software is established to track fish and robots and afford behavioral teleporting. In a series of preliminary experiments, we examine the appraisal of the teleported zebrafish by the live animal and explore the potential use of the approach to study the basis of leadership and conduct unprecedented studies on drug administration. Behavioral analysis shows that behavioral teleporting is a viable strategy to afford remote interactions between zebrafish, laying the foundations for a new area of exploration in behavioral, neurological, and pharmacological studies.