Stickiness in shear: stiffness, shape, and sealing in bioinspired suction cups affect shear performance on diverse surfaces.

Aquatic organisms utilizing attachment often contend with unpredictable environments that can dislodge them from substrates. To counter these forces, many organisms (e.g. fish, cephalopods) have evolved suction-based organs for adhesion. Morphology is diverse, with some disc shapes deviating from a circle to more ovate designs. Inspired by the diversity of multiple aquatic species, we investigated how bioinspired cups with different disc shapes performed in shear loading conditions. These experiments highlighted pertinent physical characteristics found in biological discs (regions of stiffness, flattened margins, a sealing rim), as well as ecologically relevant shearing conditions. Disc shapes of fabricated cups included a standard circle, ellipses, and other bioinspired designs. To consider the effects of sealing, these stiff silicone cups were produced with and without a soft rim. Cups were tested using a force-sensing robotic arm, which directionally sheared them across surfaces of varying roughness and compliance in wet conditions while measuring force. In multiple surface and shearing conditions, elliptical and teardrop shapes outperformed the circle, which suggests that disc shape and distribution of stiffness may play an important role in resisting shear. Additionally, incorporating a soft rim increased cup performance on rougher substrates, highlighting interactions between the cup materials and surfaces asperities. To better understand how these cup designs may resist shear, we also utilized a visualization technique (frustrated total internal reflection; FTIR) to quantify how contact area evolves as the cup is sheared.

An in situ digital synthesis strategy for the discovery and description of ocean life.

Revolutionary advancements in underwater imaging, robotics, and genomic sequencing have reshaped marine exploration. We present and demonstrate an interdisciplinary approach that uses emerging quantitative imaging technologies, an innovative robotic encapsulation system with in situ RNA preservation and next-generation genomic sequencing to gain comprehensive biological, biophysical, and genomic data from deep-sea organisms. The synthesis of these data provides rich morphological and genetic information for species description, surpassing traditional passive observation methods and preserved specimens, particularly for gelatinous zooplankton. Our approach enhances our ability to study delicate mid-water animals, improving research in the world's oceans.

Investigating Changes in Muscle Coordination During Cycling with Soft Wearable Strain Sensors Sensitive to Muscle Deformation.

Continuous monitoring of muscle coordination can provide valuable information regarding an individual's performance during physical activities. For example, changes in muscle coordination can indicate muscle fatigue during exhaustive exercise or can be used to track the rehabilitation progress of patients post-injury. Traditional methods to evaluate coordination often focus solely on measuring muscle activation with electromyography, ignoring timing changes of the resultant force produced by the activated muscle. Setups designed to evaluate force directly to study muscle coordination are often limited by either hyper-constrained settings or cost-prohibitive hardware. In this paper, we employ wearable, ultra-sensitive soft strain sensors that track muscle deformation for estimating changes in muscle coordination during cycling at different cadences and to exhaustion. The results were compared to muscle activation timing measured by electromyography and peak force timing measured by a cycle ergometer. We demonstrate that with an increase in cadence, the soft strain sensor and ergometer timing metrics align more closely than those measured by electromyography. We also demonstrate how muscle coordination is altered with the onset of fatigue during cycling to exhaustion.

Increasing the payload capacity of soft robot arms by localized stiffening.

Soft robot arms offer safety and adaptability due to their passive compliance, but this compliance typically limits their payload capacity and prevents them from performing many tasks. This paper presents a model-based design approach to effectively increase the payload capacity of soft robot arms. The proposed approach uses localized body stiffening to decrease the compliance at the end effector without sacrificing the robot's range of motion. This approach is validated on both a simulated and a real soft robot arm, where experiments show that increasing the stiffness of localized regions of their bodies reduces the compliance at the end effector and increases the height to which the arm can lift a payload. By increasing the payload capacity of soft robot arms, this approach has the potential to improve their efficacy in a variety of tasks including object manipulation and exploration of cluttered environments.

A compact DEA-based soft peristaltic pump for power and control of fluidic robots.

Fluid-driven robotic systems typically use bulky and rigid power supplies, considerably limiting their mobility and flexibility. Although various forms of low-profile soft pumps have been demonstrated, they either are limited to specific working fluids or generate limited flow rates or pressures, making them ill-suited for widespread robotics applications. In this work, we introduce a class of centimeter-scale soft peristaltic pumps for power and control of fluidic robots. An array of high power density robust dielectric elastomer actuators (DEAs) (each weighing 1.7 grams) were adopted as soft motors, operated in a programmed pattern to produce pressure waves in a fluidic channel. We investigated and optimized the dynamic performance of the pump by analyzing the interaction between the DEAs and the fluidic channel with a fluid-structure interaction finite element model. Our soft pump achieved a maximum blocked pressure of 12.5 kilopascals and a run-out flow rate of 39 milliliters per minute with a response time of less than 0.1 second. The pump can generate bidirectional flow and adjustable pressure through control of drive parameters such as voltage and phase shift. Furthermore, the use of peristalsis makes the pump compatible with various liquids. To illustrate the versatility of the pump, we demonstrate mixing a cocktail, powering custom actuators for haptic devices, and performing closed-loop control of a soft fluidic actuator. This compact soft peristaltic pump opens up possibilities for future on-board power sources for fluid-driven robots in a variety of applications, including food handling, manufacturing, and biomedical therapeutics.

High-throughput segmentation, data visualization, and analysis of sea star skeletal networks.

The remarkably complex skeletal systems of the sea stars (Echinodermata, Asteroidea), consisting of hundreds to thousands of individual elements (ossicles), have intrigued investigators for more than 150 years. While the general features and structural diversity of isolated asteroid ossicles have been well documented in the literature, the task of mapping the spatial organization of these constituent skeletal elements in a whole-animal context represents an incredibly laborious process, and as such, has remained largely unexplored. To address this unmet need, particularly in the context of understanding structure-function relationships in these complex skeletal systems, we present an integrated approach that combines micro-computed tomography, automated ossicle segmentation, data visualization tools, and the production of additively manufactured tangible models to reveal biologically relevant structural data that can be rapidly analyzed in an intuitive manner. In the present study, we demonstrate this high-throughput workflow by segmenting and analyzing entire skeletal systems of the giant knobby star, Pisaster giganteus, at four different stages of growth. The in-depth analysis, presented herein, provides a fundamental understanding of the three-dimensional skeletal architecture of the sea star body wall, the process of skeletal maturation during growth, and the relationship between skeletal organization and morphological characteristics of individual ossicles. The widespread implementation of this approach for investigating other species, subspecies, and growth series has the potential to fundamentally improve our understanding of asteroid skeletal architecture and biodiversity in relation to mobility, feeding habits, and environmental specialization in this fascinating group of echinoderms.

Toward Soft Wearable Strain Sensors for Muscle Activity Monitoring.

The force-generating capacity of skeletal muscle is an important metric in the evaluation and diagnosis of musculoskeletal health. Measuring changes in muscle force exertion is essential for tracking the progress of athletes during training, for evaluating patients' recovery after muscle injury, and also for assisting the diagnosis of conditions such as muscular dystrophy, multiple sclerosis, or Parkinson's disease. Traditional hardware for strength evaluation requires technical training for operation, generates discrete time points for muscle assessment, and is implemented in controlled settings. The ability to continuously monitor muscle force without restricting the range of motion or adapting the exercise protocol to suit specific hardware would allow for a richer dataset that can help unlock critical features of muscle health and strength evaluation. In this paper, we employ wearable, ultra-sensitive soft strain sensors for tracking changes in muscle deformation during contractions. We demonstrate the sensors' sensitivity to isometric contractions, as well as the sensors' capacity to track changes in peak torque over the course of an isokinetic fatiguing protocol for the knee extensors. The wearable soft system was able to efficiently estimate peak joint torque reduction caused by muscle fatigue (mean NRMSE = 0.15±0.03 ).

A Wearable Textile-Embedded Dielectric Elastomer Actuator Haptic Display.

With advances in mobile computing and virtual/augmented reality technologies, communicating through touch using wearable haptic devices is poised to enrich and augment current information delivery channels that typically rely on sight and hearing. To realize a wearable haptic device capable of effective data communication, both ergonomics and haptic performance (i.e., array size, bandwidth, and perception accuracy) are essential considerations. However, these goals often involve challenging and conflicting requirements. We present an integrated approach to address these conflicts, which includes incorporating multilayered dielectric elastomer actuators, a lumped-parameter model of the skin, and a wearable frame in the design loop. An antagonistic arrangement-consisting of an actuator deforming the skin-was used to achieve effective force transmission while maintaining a low profile, and the effect of the wearable frame and structure was investigated through lumped-model analysis and human perception studies.

Toward understanding the communication in sperm whales.

Machine learning has been advancing dramatically over the past decade. Most strides are human-based applications due to the availability of large-scale datasets; however, opportunities are ripe to apply this technology to more deeply understand non-human communication. We detail a scientific roadmap for advancing the understanding of communication of whales that can be built further upon as a template to decipher other forms of animal and non-human communication. Sperm whales, with their highly developed neuroanatomical features, cognitive abilities, social structures, and discrete click-based encoding make for an excellent model for advanced tools that can be applied to other animals in the future. We outline the key elements required for the collection and processing of massive datasets, detecting basic communication units and language-like higher-level structures, and validating models through interactive playback experiments. The technological capabilities developed by such an undertaking hold potential for cross-applications in broader communities investigating non-human communication and behavioral research.

Advances and future outlooks in soft robotics for minimally invasive marine biology.

This Viewpoint describes interdisciplinary research that aims to maximize understanding of deep marine life, while concurrently being minimally invasive. We describe the synthesis of multiple modern approaches (spanning robotics, biology, biomechanics, engineering, imaging, and genomic sequencing) and present future directions that hold the potential for a paradigm shift in marine biology.

An Ambidextrous STarfish-Inspired Exploration and Reconnaissance Robot (The ASTER-bot).

As more roboticists are turning to Nature for design inspiration, it is becoming increasingly apparent that multisystem-level investigations of biological processes can frequently lead to unexpected advances in the development of experimental research platforms. Inspired by these efforts, we present here a holistic approach to developing an autonomous starfish-inspired soft robot that embodies a number of key design, fabrication, and actuation principles. These key concepts include integrated and sequentially deployable magnetic tube feet for site-specific and reversible substrate attachment, individually addressable flexible arms, and highly efficient and self-contained fluidic engines. These individual features offer a level of synergistic motion control not previously seen in other starfish-inspired robots. For example, our bistable dome-like tube feet are capable of achieving high adhesion forces to ferrous surfaces and low removal forces. These tube feet are further integrated with a fluidic engine to drive the entire arm while maintaining the ability to accurately control the arm position with a 270° range of motion. Furthermore, the arm and fluidic engine are modular, allowing each of the five arms to be replaced in seconds or enabling the exploration of a variety of limb geometries. Through the incorporation of these different design elements, the ASTER-bot (named for its star-like body plan) is capable of locomotion on ferrous surfaces, above and below water, and on nonplanar surfaces. This article further describes the design, fabrication, and integration strategies and characterizes the energetic and locomotory performance of this pentaradial robotic prototype.

Scaling Up Soft Robotics: A Meter-Scale, Modular, and Reconfigurable Soft Robotic System.

Today's use of large-scale industrial robots is enabling extraordinary achievement on the assembly line, but these robots remain isolated from the humans on the factory floor because they are very powerful, and thus dangerous to be around. In contrast, the soft robotics research community has proposed soft robots that are safe for human environments. The current state of the art enables the creation of small-scale soft robotic devices. In this article we address the gap between small-scale soft robots and the need for human-sized safe robots by introducing a new soft robotic module and multiple human-scale robot configurations based on this module. We tackle large-scale soft robots by presenting a modular and reconfigurable soft robotic platform that can be used to build fully functional and untethered meter-scale soft robots. These findings indicate that a new wave of human-scale soft robots can be an alternative to classic rigid-bodied robots in tasks and environments where humans and machines can work side by side with capabilities that include, but are not limited to, autonomous legged locomotion and grasping.

An insect-scale robot reveals the effects of different body dynamics regimes during open-loop running in feature-laden terrain.

The transition from the lab to natural environments is an archetypal challenge in robotics. While larger robots can manage complex limb-ground interactions using sensing and control, such strategies are difficult to implement on small platforms where space and power are limited. The Harvard Ambulatory Microrobot (HAMR) is an insect-scale quadruped capable of effective open-loop running on featureless, hard substrates. Inspired by the predominantly feedforward strategy of rapidly-running cockroaches on uneven terrain (Sponberg, 2007), we used HAMR to explore open-loop running on two 3D printed heterogeneous terrains generated using fractional Brownian motion. The 'pocked' terrain had foot-scale features throughout while the 'jagged' terrain features increased in height in the direction of travel. We measured the performance of trot and pronk gaits while varying limb amplitude and stride frequency. The frequencies tested encompassed different dynamics regimes: body resonance (10-25 Hz) and kinematic running (30-40 Hz), with dynamics typical of biological running and walking, respectively, and limb-transmission resonance (45-60 Hz). On the featureless and pocked terrains, low mechanical cost-of-transport (mCoT) kinematic running combinations performed best without systematic differences between trot and pronk; indicating that if terrain features are not too tall, a robot can transition from homo-to heterogeneous environments in open-loop. Pronk bypassed taller features than trot on the jagged terrain, and higher mCoT, lower frequency running was more often effective. While increasing input power to the robot improved performance in general, lower frequency pronking on jagged terrain allowed the robot to bypass taller features compared with the same input power at higher frequencies. This was correlated with the increased variation in center-of-mass orientation occurring at frequencies near body resonance. This study established that appropriate choice of robot dynamics, as mediated by gait, frequency, and limb amplitude, can expand the terrains accessible to microrobots without the addition of sensing or closed-loop control.

A physical model of mantis shrimp for exploring the dynamics of ultrafast systems.

Efficient and effective generation of high-acceleration movement in biology requires a process to control energy flow and amplify mechanical power from power density-limited muscle. Until recently, this ability was exclusive to ultrafast, small organisms, and this process was largely ascribed to the high mechanical power density of small elastic recoil mechanisms. In several ultrafast organisms, linkages suddenly initiate rotation when they overcenter and reverse torque; this process mediates the release of stored elastic energy and enhances the mechanical power output of extremely fast, spring-actuated systems. Here we report the discovery of linkage dynamics and geometric latching that reveals how organisms and synthetic systems generate extremely high-acceleration, short-duration movements. Through synergistic analyses of mantis shrimp strikes, a synthetic mantis shrimp robot, and a dynamic mathematical model, we discover that linkages can exhibit distinct dynamic phases that control energy transfer from stored elastic energy to ultrafast movement. These design principles are embodied in a 1.5-g mantis shrimp scale mechanism capable of striking velocities over 26 m [Formula: see text] in air and 5 m [Formula: see text] in water. The physical, mathematical, and biological datasets establish latching mechanics with four temporal phases and identify a nondimensional performance metric to analyze potential energy transfer. These temporal phases enable control of an extreme cascade of mechanical power amplification. Linkage dynamics and temporal phase characteristics are easily adjusted through linkage design in robotic and mathematical systems and provide a framework to understand the function of linkages and latches in biological systems.

A dynamic electrically driven soft valve for control of soft hydraulic actuators.

Regulation systems for fluid-driven soft robots predominantly consist of inflexible and bulky components. These rigid structures considerably limit the adaptability and mobility of these robots. Soft valves in various forms for fluidic actuators have been developed, primarily fluidically or electrically driven. However, fluidic soft valves require external pressure sources that limit robot locomotion. State-of-the-art electrostatic valves are unable to modulate pressure beyond 3.5 kPa with a sufficient flow rate (>6 mL⋅min-1). In this work, we present an electrically powered soft valve for hydraulic actuators with mesoscale channels based on a different class of ultrahigh-power density dynamic dielectric elastomer actuators. The dynamic dielectric elastomer actuators (DEAs) are actuated at 500 Hz or above. These DEAs generate 300% higher blocked force compared with the dynamic DEAs in previous works and their loaded power density reaches 290 W⋅kg-1 at operating conditions. The soft valves are developed with compact (7 mm tall) and lightweight (0.35 g) dynamic DEAs, and they allow effective control of up to 51 kPa of pressure and a 40 mL⋅min-1 flow rate with a response time less than 0.1 s. The valves can also tune flow rates based on their driving voltages. Using the DEA soft valves, we demonstrate control of hydraulic actuators of different volumes and achieve independent control of multiple actuators powered by a single pressure source. This compact and lightweight DEA valve is capable of unprecedented electrical control of hydraulic actuators, showing the potential for future onboard motion control of soft fluid-driven robots.

Smarter materials for smarter robots.

Advances in materials science will blur the boundaries between robots and the materials from which they are composed.

Microrobotic laser steering for minimally invasive surgery.

The creation of multiarticulated mechanisms for use with minimally invasive surgical tools is difficult because of fabrication, assembly, and actuation challenges on the millimeter scale of these devices. Nevertheless, such mechanisms are desirable for granting surgeons greater precision and dexterity to manipulate and visualize tissue at the surgical site. Here, we describe the construction of a complex optoelectromechanical device that can be integrated with existing surgical tools to control the position of a fiber-delivered laser. By using modular assembly and a laminate fabrication method, we are able to create a smaller and higher-bandwidth device than the current state of the art while achieving a range of motion similar to existing tools. The device we present is 6 millimeters in diameter and 16 millimeters in length and is capable of focusing and steering a fiber-delivered laser beam at high speed (1.2-kilohertz bandwidth) over a large range (over ±10 degrees in both of two axes) with excellent static repeatability (200 micrometers).

Complete Electrolytic Plastron Recovery in a Low Drag Superhydrophobic Surface.

We present a superhydrophobic surface capable of recovering the lubricious gas layer known as the "plastron" from a fully wetted state underwater. It is shown that full plastron recovery is possible without a second layer of structural hierarchy, which is prone to irreversible wetting transitions. This allows us to use a cheap, fast, and potentially scalable method to fabricate the surface from silicone and carbon black in a molding process. We demonstrate plastron recovery from the fully wetted state and immediate plastron recovery after pressure-induced wetting transitions. The wetting state can be measured remotely and quickly by measuring the capacitance. The slip length is measured as ∼135 µm, agreeing well with the theory given the geometry of the surface. The ability of the surface to conform to small radii of curvature and withstand damage from loading is also demonstrated. The work presented here could allow superhydrophobic surfaces to reduce drag on ships and in pipes where the plastron would otherwise rapidly dissolve.

Velopharyngeal Muscle Morphology in Children With Unrepaired Submucous Cleft Palate: An Imaging Study.

OBJECTIVE: To identify quantitative and qualitative differences in the velopharyngeal musculature and surrounding structures between children with submucous cleft palate (SMCP) and velopharyngeal insufficiency (VPI) and noncleft controls with normal anatomy and normal speech. METHODS: Magnetic resonance imaging was used to evaluate the velopharyngeal mechanism in 20 children between 4 and 9 years of age; 5 with unrepaired SMCP and VPI. Quantitative and qualitative measures of the velum and levator veli palatini in participants with symptomatic SMCP were compared to noncleft controls with normal velopharyngeal anatomy and normal speech. RESULTS: Analysis of covariance revealed that children with symptomatic SMCP demonstrated increased velar genu angle (15.6°, P = .004), decreased α angle (13.2°, P = .37), and longer (5.1 mm, P = .32) and thinner (4 mm, P = .005) levator veli palatini muscles compared to noncleft controls. Qualitative comparisons revealed discontinuity of the levator muscle through the velar midline and absence of a musculus uvulae in children with symptomatic SMCP compared to noncleft controls. CONCLUSIONS: The levator veli palatini muscle is longer, thinner, and discontinuous through the velar midline, and the musculus uvulae is absent in children with SMCP and VPI compared to noncleft controls. The overall velar configuration in children with SMCP and VPI is disadvantageous for achieving adequate velopharyngeal closure necessary for nonnasal speech compared to noncleft controls. These findings add to the body of literature documenting levator muscle, musculus uvulae, and velar and craniometric parameters in children with SMCP.