Fig 4 - uploaded by Barry Andrew Trimmer
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The upper and lower tracks of proleg-retractor muscles are traced during a crawl. (A) In mid-body segment A3, the proleg does not shorten (tracks are parallel) and the angle changes very little. (B) In contrast, the terminal prolegs shorten and extend each cycle and are held at a pronounced angle during stance. Crawling kinematics are quantified in detail (Trimmer and Issberner 2007).
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Muscular hydrostats (such as mollusks), and fluid-filled animals (such as annelids), can exploit their constant-volume tissues to transfer forces and displacements in predictable ways, much as articulated animals use hinges and levers. Although larval insects contain pressurized fluids, they also have internal air tubes that are compressible and, a...
Citations
... The main design inspiration has been bionics [16]. Trimmer et al. [17] designed a caterpillar bionic robot. Jin et al. [18] took the muscle organs of mollusks as inspiration and assembled modular soft robots with various forms based on a shape memory alloy. ...
In order to study the influence of the cavity inclination angle bending performance of pneumatic soft actuators, two kinds of soft actuators were designed, one with a five-degree-angle cavity structure, and the other with a hybrid variable-degree-angle cavity structure. The bending performance of zero-degree-angle, five-degree-angle, and hybrid variable-degree-angle soft actuators was investigated by experimental methods and the ABAQUS finite element simulation method. The results show that, under seven different pressure loads, the mean absolute error between the experimental results and the numerical simulation results for the zero-degree-angle soft actuator was 0.926, for the five-degree-angle soft actuator it was 1.472, and for the hybrid variable-degree-angle soft actuator it was 1.22. When the pressure load changed from 4 kPa to 16 kPa, the five-degree-angle soft actuator had the largest range-of-angle variation, with the bending angle increasing 193.31%, from 26.92 degrees to 78.97 degrees. In the same longitudinal displacement, the five-degree-angle soft actuator had the largest lateral displacement variation, and the bending effect was the best compared with the zero-degree-angle soft actuator and the hybrid variable-degree-angle soft actuator. According to the experimental and numerical simulation results, with the same structural parameter design, the cavity tilt angle increases, which can increase the bending angle variation range and improve the bending performance of soft actuators.
... Then, we recorded the resistance change of the SWCNT/BBE sensor with the crawling of the hornworm, and the long-term electrical response shows that our SWCNT/BBE sensor can easily record the movements of the hornworm without detaching ( Fig. 4h and Supplementary Movie 7). The capability of conducting demonstrations with soft-bodied animals could possibly inspire research on biomechanics 66 and robot designs 67 . These results highlight the great potential of our conductive SWCNT/BBE as an ultracompliant and sensitive material for soft robotic and wearable sensing. ...
Understanding biological systems and mimicking their functions require electronic tools that can interact with biological tissues with matched softness. These tools involve biointerfacing materials that should concurrently match the softness of biological tissue and exhibit suitable electrical conductivities for recording and reading bioelectronic signals. However, commonly employed intrinsically soft and stretchable materials usually contain solvents that limit stability for long-term use or possess low electronic conductivity. To date, an ultrasoft (i.e., Young’s modulus <30 kPa), conductive, and solvent-free elastomer does not exist. Additionally, integrating such ultrasoft and conductive materials into electronic devices is poorly explored. This article reports a solvent-free, ultrasoft and conductive PDMS bottlebrush elastomer (BBE) composite with single-wall carbon nanotubes (SWCNTs) as conductive fillers. The conductive SWCNT/BBE with a filler concentration of 0.4 − 0.6 wt% reveals an ultralow Young’s modulus (<11 kPa) and satisfactory conductivity (>2 S/m) as well as adhesion property. Furthermore, we fabricate ultrasoft electronics based on laser cutting and 3D printing of conductive and non-conductive BBEs and demonstrate their potential applications in wearable sensing, soft robotics, and electrophysiological recording.
... In this context, caterpillars are of particular interest. They are simply shaped animals whose locomotion mechanism is based on pressurizing units of connected soft cylinders that endow caterpillars with the capacity to display large deformations and also climb complex three-dimensional environments with only a few muscle groups [17,[32][33]. During locomotion, caterpillars use the substrate to transmit forces from each contact point to other parts of the body. ...
... During locomotion, caterpillars use the substrate to transmit forces from each contact point to other parts of the body. This is biomechanically distinct from most of the soft-bodied terrestrial animals that crawl through stiff hydrostatic structures [32][33]. By controlling the timing and location of this substrate attachment through their legs and prolegs, caterpillars can move forward by crawling, inching, or a combination of both motion modes [18,[34][35][36][37][38]. ...
... Manduca sexta is one of the simplest and most studied caterpillars since it only moves via a crawling motion. Crawling in a caterpillar consists of a broad longitudinal peristaltic contraction wave (anterograde wave), and it moves forward through successive phase delays, presenting a tail-to-head propagation that is the opposite of the head-to-tail contraction wave observed in earthworms (retrograde wave) [33,[37][38][39][40]. This wave of muscle contraction (peristalsis) serves primarily to reduce the grip between the body and the substrate, and redistribute mechanical energy stored in elastic tissues [15,32,[39][40]. ...
Mechanical instabilities are emerging as novel actuation mechanisms for the design of biomimetic soft robots and smart structures. The present study shows that by coupling buckling-driven elastomeric auxetic modules actuated by a negative air-pressure, a novel metamaterial-based caterpillar can be designed-the Metarpillar. Following a detailed analysis of the caterpillar's locomotion, we were able to mimic both its crawling movement and locomotion by using the unique isometric compression of the modules and properly programing the anterograde modular peristaltic contractions. The bioinspired locomotion of the Metarpillar uses the bending triggered by the buckling-driven module contraction to control the friction through a dynamic anchoring between the soft robot and the surface, which is the main mechanism for locomotion in caterpillars and other crawling organisms. Thus, the Metarpillar not only mimics the locomotion of the caterpillar but also displays dynamic similarity and equivalent, or even faster, speeds. Our approach based on metamaterial buckling actuator units opens up a novel strategy for biomimetic soft robotic locomotion that can be extended beyond caterpillars.
... In nature, there are numerous examples of how programmed mechanical forces help organisms adapt to their environment. Mimosa pudica folds its leaves inward upon touching or shaking as a defense mechanism, [1] caterpillars use waves of deformation to move, [2] and the Venus flytrap closes its trapping leaves in response to the minute force of an insect landing on it. [3] Hydrogel-based mechanically active materials (MAMs)-also called artificial muscle, actuators, or force sensing materials-can either generate mechanical force or respond to mechanical force, and have been heavily inspired by nature. ...
Programmable mechanically active materials (MAMs) are defined as materials that can sense and transduce external stimuli into mechanical outputs or conversely that can detect mechanical stimuli and respond through an optical change or other change in the appearance of the material. Programmable MAMs are a subset of responsive materials and offer potential in next generation robotics and smart systems. This review specifically focuses on hydrogel‐based MAMs because of their mechanical compliance, programmability, biocompatibility, and cost‐efficiency. First, the composition of hydrogel MAMs along with the top‐down and bottom‐up approaches used for programming these materials are discussed. Next, the fundamental principles for engineering responsivity in MAMS, which includes optical, thermal, magnetic, electrical, chemical, and mechanical stimuli, are considered. Some advantages and disadvantages of different responsivities are compared. Then, to conclude, the emerging applications of hydrogel‐based MAMs from recently published literature, as well as the future outlook of MAM studies, are summarized. Hydrogel‐based mechanically active materials (MAMs) are a diverse class of materials that are able to sense and respond to external stimuli by producing a physical deformation. The state‐of‐the‐art programming of MAMs in recent studies is highlighted. Materials, fabrication methods, responsive mechanisms, and novel applications of hydrogel MAMs are systematically discussed.
... They lack defined joints and instead move by deforming limbs, changing the shape of their body and exerting internal hydrostatic or hydraulic forces (Kier, 2012). For such animals, the shape and mechanical properties of soft tissues play a much more significant role in generating and controlling movements (Buschmann and Trimmer, 2017;Hanassy et al., 2015;Levy et al., 2015Levy et al., , 2017Richter et al., 2015;Sumbre et al., 2005;Trimmer and Lin, 2014;Yekutieli et al., 2005). There are major technical challenges to understanding how the nervous systems of soft animals cope with these increased degrees of freedom. ...
Manduca sexta larvae are an important model system for studying the neuromechanics of soft body locomotion. They climb on plants using the abdominal prolegs to grip and maneuver in any orientation and on different surfaces. The prolegs grip passively with an array of cuticular hooks and grip release is actively controlled by retractor muscles inserted into the soft planta membrane at the proleg tip. Until now, the principal planta retractor muscles (PPRMs) in each body segment were thought to be a single fiber bundle originating on the lateral body wall. Here, using high resolution X-ray microtomography of intact animals, we show that PPRM is a more complex muscle consisting of multiple contractile fibers originating at several distinct sites on the proleg. Furthermore, we show that there are segmental differences in the number and size of some of these fiber groups which suggests that the prolegs may operate differently along the anterior-posterior axis.
... The walking gait of our robot is composed of four consecutive quasi-static states that are inspired by the planar quadrupedal bounding (Alexander, 1984) and a caterpillar inching motion (Trimmer and Lin, 2014). These states are depicted as (1) relaxed, (2) front-stance, (3) double-stance, and (4) back-stance as shown in Figures 1(c)-(f). ...
Untethered small-scale soft robots have promising applications in minimally invasive surgery, targeted drug delivery, and bioengineering applications as they can directly and non-invasively access confined and hard-to-reach spaces in the human body. For such potential biomedical applications, the adaptivity of the robot control is essential to ensure the continuity of the operations, as task environment conditions show dynamic variations that can alter the robot’s motion and task performance. The applicability of the conventional modeling and control methods is further limited for soft robots at the small-scale owing to their kinematics with virtually infinite degrees of freedom, inherent stochastic variability during fabrication, and changing dynamics during real-world interactions. To address the controller adaptation challenge to dynamically changing task environments, we propose using a probabilistic learning approach for a millimeter-scale magnetic walking soft robot using Bayesian optimization (BO) and Gaussian processes (GPs). Our approach provides a data-efficient learning scheme by finding the gait controller parameters while optimizing the stride length of the walking soft millirobot using a small number of physical experiments. To demonstrate the controller adaptation, we test the walking gait of the robot in task environments with different surface adhesion and roughness, and medium viscosity, which aims to represent the possible conditions for future robotic tasks inside the human body. We further utilize the transfer of the learned GP parameters among different task spaces and robots and compare their efficacy on the improvement of data-efficient controller learning.
... The field of soft robotics endeavors to reproduce the versatility of natural organismsin particular their ability to interact effectively with uncertain and dynamic external forces or environments-through the incorporation of elasticity and compliance into robotic structures. [1][2][3][4][5][6][7][8][9][10][11][12] Naturally, softbodied animals [13] that undergo continuum deformation, such as annelids, [14] insect larvae, [15] and molluscs, [16] are often used as model organisms in soft robotics. [17][18][19] However, the functional capabilities of these soft robots, such as weight support against gravity, [20] body/appendage control, [21] and rapid propulsion, [22] could be further enhanced by incorporating arthropod-inspired articulated exoskeletal mechanisms [23] comprised of both rigid and compliant elements, all while maintaining impressive compliance, e.g., for navigating confined spaces. ...
The impressive locomotion and manipulation capabilities of spiders have led to a host of bioinspired robotic designs aiming to reproduce their functionalities; however, current actuation mechanisms are deficient in either speed, force output, displacement, or efficiency. Here—using inspiration from the hydraulic mechanism used in spider legs—soft‐actuated joints are developed that use electrostatic forces to locally pressurize a hydraulic fluid, and cause flexion of a segmented structure. The result is a lightweight, low‐profile articulating mechanism capable of fast operation, high forces, and large displacement; these devices are termed spider‐inspired electrohydraulic soft‐actuated (SES) joints. SES joints with rotation angles up to 70°, blocked torques up to 70 mN m, and specific torques up to 21 N m kg⁻¹ are demonstrated. SES joints demonstrate high speed operation, with measured roll‐off frequencies up to 24 Hz and specific power as high as 230 W kg⁻¹—similar to human muscle. The versatility of these devices is illustrated by combining SES joints to create a bidirectional joint, an artificial limb with independently addressable joints, and a compliant gripper. The lightweight, low‐profile design, and high performance of these devices, makes them well‐suited toward the development of articulating robotic systems that can rapidly maneuver.
... The field of robotics and control could learn a lot from how animals control motion and adapt to extreme perturbations such as the loss of one or more limbs (Trimmer and Lin, 2014;Chattunyakit et al., 2019;Kano et al., 2019). This is especially important for robots deployed in the field for long term missions such as deep sea or space exploration (Koos et al., 2013). ...
Animals are incredibly good at adapting to changes in their environment, a trait envied by most roboticists. Many animals use different gaits to seamlessly transition between land and water and move through non-uniform terrains. In addition to adjusting to changes in their environment, animals can adjust their locomotion to deal with missing or regenerating limbs. Salamanders are an amphibious group of animals that can regenerate limbs, tails, and even parts of the spinal cord in some species. After the loss of a limb, the salamander successfully adjusts to constantly changing morphology as it regenerates the missing part. This quality is of particular interest to roboticists looking to design devices that can adapt to missing or malfunctioning components. While walking, an intact salamander uses its limbs, body, and tail to propel itself along the ground. Its body and tail are coordinated in a distinctive wave-like pattern. Understanding how their bending kinematics change as they regrow lost limbs would provide important information to roboticists designing amphibious machines meant to navigate through unpredictable and diverse terrain. We amputated both hindlimbs of blue-spotted salamanders ( Ambystoma laterale ) and measured their body and tail kinematics as the limbs regenerated. We quantified the change in the body wave over time and compared them to an amphibious fish species, Polypterus senegalus . We found that salamanders in the early stages of regeneration shift their kinematics, mostly around their pectoral girdle, where there is a local increase in undulation frequency. Amputated salamanders also show a reduced range of preferred walking speeds and an increase in the number of bending waves along the body. This work could assist roboticists working on terrestrial locomotion and water to land transitions.
... The walking gait of our robot is composed of four consecutive quasi-static states that are inspired by the planar quadrupedal bounding [1] and a caterpillar's inching motion [39]. These states are depicted as (1) relaxed, (2) front-stance, (3) double-stance, and (4) back-stance as shown in Fig. 1d. ...
Untethered small-scale soft robots have promising applications in minimally invasive surgery, targeted drug delivery , and bioengineering applications as they can access confined spaces in the human body. However, due to highly nonlin-ear soft continuum deformation kinematics, inherent stochastic variability during fabrication at the small scale, and lack of accurate models, the conventional control methods cannot be easily applied. Adaptivity of robot control is additionally crucial for medical operations, as operation environments show large variability, and robot materials may degrade or change over time, which would have deteriorating effects on the robot motion and task performance. Therefore, we propose using a probabilistic learning approach for millimeter-scale magnetic walking soft robots using Bayesian optimization (BO) and Gaussian processes (GPs). Our approach provides a data-efficient learning scheme to find controller parameters while optimizing the stride length performance of the walking soft millirobot robot within a small number of physical experiments. We demonstrate adaptation to fabrication variabilities in three different robots and to walking surfaces with different roughness. We also show an improvement in the learning performance by transferring the learning results of one robot to the others as prior information.
... sawfly larvae) and most Lepidoptera (caterpillars, the larval stages of moths and butterflies) (Hinton, 1955). Locomotion in caterpillars is generally described as either inching or crawling (van Griethuijsen and Trimmer, 2014): inching is characterized by sequences of long steps, often involving the whole body, in which anterior and posterior contact points alternate their swing phase (Trimmer and Lin, 2014); in contrast, crawling is characterized by a forwardmoving abdominal wave ( posterior-to-anterior movement of successive body segments that shorten and typically lift upward) that progresses as the prolegs successively release their grip, move through a swing phase to a new forward position, and then re-attach to the substrate. ...
... Despite this, one question has yet to be addressed: what is the role of the central motor programs in coordinating different gaits? We have previously proposed that inching evolved from crawling by eliminating mid-body gripping (Trimmer and Lin, 2014), and that this could be accomplished through a loss of mechanical function (e.g. mutations that prevent formation of the crochets; Suzuki and Palopoli, 2001;Xiang et al., 2011) or by changes in motor commands controlling the retractor muscles. ...
Most animals can successfully travel across cluttered, uneven environments and cope with enormous changes in surface friction, deformability, and stability. However, the mechanisms used to achieve such remarkable adaptability and robustness are not fully understood. Even more limited is the understanding of how soft, deformable animals such as tobacco hornworm Manduca sexta (caterpillars) can control their movements as they navigate surfaces that have varying stiffness and are oriented at different angles. To fill this gap, we analyzed the stepping patterns of caterpillars crawling on two different types of substrates (stiff and soft) and in three different orientations (horizontal and upward/downward vertical). Our results show that caterpillars adopt different stepping patterns (i.e. different sequences of transition between the swing and stance phases of prolegs in different body segments) based on substrate stiffness and orientation. These changes in stepping patterns occur more frequently in the upward vertical orientation. The results of this study suggest that caterpillars can detect differences in the material properties of the substrate on which they crawl and adjust their behavior to match those properties.
