Soft Body Research Articles

Snapping for high-speed and high-efficient butterfly stroke-like soft swimmer.

Natural selection has tuned many flying and swimming animals to share the same narrow design space for high power efficiency, e.g., their dimensionless Strouhal numbers St that relate flapping frequency and amplitude and forward speed fall within the range of 0.2 < St < 0.4 for peak propulsive efficiency. It is rather challenging to achieve both comparably fast-speed and high-efficient soft swimmers to marine animals due to the naturally selected narrow design space and soft body compliance. Here, bioinspired by the flapping motion in swimming animals, we report leveraging snapping instabilities for soft flapping-wing swimmers with comparable high performance to biological counterparts. The lightweight, butterfly stroke-like soft swimmer (2.8 g) demonstrates a record-high speed of 3.74 body length/s (4.8 times faster than the reported fastest flapping soft swimmer), high power efficiency (0.2 < St = 0.25 < 0.4), low energy consumption cost, and high maneuverability (a high turning speed of 157°/s).

Characteristics of a small arbitrary walking and jumping composite soft actuator with origami structure

A small arbitrary walking and jumping actuator with a composited structure and size of 7 cm × 4 cm × 2.5 cm and mass of 5 g is proposed. An origami structure of polyvinyl chloride (PVC) membrane is designed for the main soft body, driven by shape memory alloy (SMA) springs and piezoelectric bimorphs. It has jumping, linear, and rotating motion modes. A simplified multi-faceted model by MATLAB software is established to perform a numerical analysis of the dynamics of jumping motion. Calculated results show that the length of the elastic belts have a directly proportional impact on the takeoff velocity, jumping legs orientation angle, shape and size of the body and air drag variably impact the jumping performance. The measured results show that the jumping height and distance are 10.3 cm and 19.8 cm, respectively, with a response time of 6.7 s at 1.4 A. The maximum rotating speed on the sandpaper and flat worktop are about 100 deg/s and 300 deg/s respectively. Its linear speed is more than 10 cm/s. • A small arbitrary walking and jumping actuator with composited structure is proposed. • A simplified multi-faceted model of jumping motion is established. • This actuator can jump and recover without motion failure.

A Lightweight and Multimotion Crawling Tensegrity Robot Driven by Twisted Artificial Muscles

Soft robots made from soft materials show great advantages over rigid robots in environmental adaptability and motion flexibility. However, too soft body makes them lose the load capacity, which limits their applications in locomotion. Although the crawling tensegrity robots with both rigid bars and flexible cables are potential to address this challenge, the existing inchworm friction drive methods are difficult to realize the motion of a single tensegrity unit. Besides, the lack of appropriate soft actuators and robot configuration also blocks the development of the crawling tensegrity robots. This article presents a new inchworm driving method realized by the inclined supporting feet. By using the twisted artificial muscle (TAM) as actuator, the combination of the TAM and the inclined supporting feet endows a single three-bar tensegrity unit with multimotion capacity and anisotropic stiffness characteristics. The designed tensegrity robot not only has high compliance but also displays high stiffness, which endows it with high load capacity. The prototype can carry a load of 150 g (7.5 times of its weight) to achieve straight and turning motions. This article provides a design idea for the crawling tensegrity robot and a theoretical foundation for improving the load capacity of high compliance robots.

Evaluation of a Peak-Free Chemometric Laser-Induced Breakdown Spectroscopy Method for Direct Rapid Cancer Detection via Trace Metal Biomarkers in Tissue

The ability to perform direct rapid analysis in air and at atmospheric pressure is a remarkable attraction of laser-induced breakdown spectroscopy (LIBS) for the diagnostic quantification of disease biomarker metals in body tissue. However, accurate trace analysis is limited by matrix effects and a pronounced background that masks the subtle (peak-free) analyte signals because tissue plasma is dense and most lines are optically thick. In this work, a peak-free chemometric LIBS method based on a single-shot (for rapidity and nondestructiveness) and an artificial neural network multivariate calibration strategy with spectral feature selection was evaluated for its utility for direct trace quantitative analysis of copper (Cu), iron (Fe), manganese (Mg), magnesium (Mg), and zinc (Zn) in model soft body tissue. The spectral signatures corresponding to the biometals (so-called because the metals are intrinsic to tissue biochemistry) were generated by spiking their known human-body-representative concentrations in molten paraffin wax. The developed multivariate analytical model achieved ≥95% accuracy as determined from the analysis of oyster tissue-certified reference material. The analytical models were tested on the liver, breast, and abdominal tissue biopsies. The results of applying the model to the clinical tissues indicated the absence or presence (including severity) of cancer as either malignant or benign, in agreement with the pathological examination report.

The application of multiple metrics in deformable image registration for target volume delineation of breast tumor bed.

For postoperative breast cancer patients, deformable image registration (DIR) is challenged due to the large deformations and non-correspondence caused by tumor resection and clip insertion. To deal with it, three metrics (fiducial-, region-, and intensity-based) were jointly used in DIR algorithm for improved accuracy. Three types of metrics were combined to form a single-objective function in DIR algorithm. Fiducial-based metric was used to minimize the distance between the corresponding point sets of two images. Region-based metric was used to improve the overlap between the corresponding areas of two images. Intensity-based metric was used to maximize the correlation between the corresponding voxel intensities of two images. The two CT images, one before surgery and the other after surgery, were acquired from the same patient in the same radiotherapy treatment position. Twenty patients who underwent breast-conserving surgery and postoperative radiotherapy were enrolled in this study. For target registration error, the difference between the proposed and the conventional registration methods was statistically significant for soft tissue (2.06 vs. 7.82, p=0.00024<0.05) and body boundary (3.70 vs. 6.93, p=0.021<0.05). For visual assessment, the proposed method achieved better matching result for soft tissue and body boundary. Comparing to the conventional method, the registration accuracy of the proposed method was significantly improved. This method provided a feasible way for target volume delineation of tumor bed in postoperative radiotherapy of breast cancer patients.

Upside-Down Brachiation Robot Using Elastic Energy Stored Through Soft Body Deformation

Storing elastic energy in a soft body and releasing it instantly enables ultrafast movement beyond muscle capability, which small animals (mainly arthropods) realize. We applied this mechanism to a soft robot to achieve locomotion on top of a tubular surface such as a branch (i.e., upside-down brachiation). To achieve arboreal locomotion, the robot must have strong grippers to support its body and minimize the duration of time when one gripper is off the branch. By using a simulation model and prototype, we demonstrated that storing and releasing elastic energy in a soft body satisfies these requirements, allowing us to fabricate a lightweight robot. The prototype completed one step of the locomotion process in 0.22 secs, making it 2.3 times faster than the original speed of the mounted motor. In addition, we confirmed that the robot climbs 0- to 90-degree branches.

Insect-Scale SMAW-Based Soft Robot With Crawling, Jumping, and Loading Locomotion

The work develops an insect-scale soft robot capable of fast directional locomotion actuated by itself spring-like body composed of shape memory alloy wires (SMAWs)-based composite. The soft composite is fabricated integrating polydimethylsiloxane (PDMS) matrix, 3D printed acrylonitrile-butadiene-styrene (ABS) substrate, and parallel multi-SMAWs with the diameter of 0.075 mm. Since it can implant the thermal-induced SMAW deformation and rapidly cause the elastic recovery feature of ABS resin material, the soft composite can act as the insect-scale robotic actuator to imitate the longitudinal muscle. The designed structure can convert the repetitive contraction-stretch behavior of the embedded SMAWs to the bending-expanding deformation of the robotic soft body, which forms the robotic different gaits. With the excitation of pulse-width modulation (PWM) voltages with various frequencies, different characteristics of the designed robot are compared. The experimental results validate that the designed soft robot can reach a movement speed of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sim$</tex-math></inline-formula> 29.87 mm/s with jumping locomotion, greater than one-time body-length/s, and afford a load of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sim$</tex-math></inline-formula> 11.1 g, about 24.1 times the weight of itself.

Ultra-stretchable, Antifatigue, Adhesive, and Self-Healing Hydrogels Based on the Amino Acid Derivative and Ionic Liquid for Flexible Strain Sensors

Multifunctional adhesive hydrogels have great potential in flexible wearable materials, smart wearable materials, and biomedical materials. However, the preparation of such hydrogels is still challenging. Here, a P(MArg-FHVI-AA) hydrogel was prepared by copolymerization of an arginine derivative monomer, ionic liquid imidazolium salt derivative monomer, and acrylic acid (AA). Based on multiple weak hydrogen bonds and electrostatic interactions, the hydrogel had the following characteristics: high transparency (>85%), ultra-stretchability (2613%), high elasticity (1000% strain cyclic for 10 times), fatigue resistance (200 cycles under 80% compressive strain), self-healing, good adhesion in air and water (37 and 32 kPa for porcine skin in air and water), and electrical conductivity. When metal ions were added to P(MArg-FHVI-AA) hydrogels, the mechanical properties of the hydrogels were enhanced (tensile strength of 109–352 kPa, stretchability of 1707–1942%), and the hydrogels exhibited stronger adhesion strength (68 kPa for porcine skin), good biocompatibility (99%), impressive antibacterial properties (100% antibacterial effect against Escherichia coli and Staphylococcus aureus), shape memory, fluorescent writing (its fluorescence intensity was 1099% of the initial), and information transfer functions. Furthermore, the P(MArg-FHVI-AA) hydrogel showed real-time performance in monitoring various motions. This work provided an idea for the construction of multifunctional and smart adhesive conductive hydrogel materials, and this hydrogel could be a promising candidate for smart wearable materials, health monitoring, and soft body materials.

Ballistic loading and survivability of optical fiber sensing layers for soft body armor evaluation

The authors previously demonstrated the use of FBG sensors in Kevlar mats behind body armor to measure the transient back face deformation (BFD) during ballistic testing. This paper presents a novel sensor system based on a Fiber Bragg Grating embedded in silicone mats to improve the survivability of the body armor in-situ strain sensing layers. Due to the large amount of deformation, a relative slip between the optical fibers and the supporting structure is needed to maintain the performance of the sensors and determine the relationship between the measured strain and deformation shape. Two silicone materials were tested, Smooth-Sil 950 and Sorta-Clear 40, in both 1 mm and 2 mm thicknesses to evaluate their survivability and impact on BFD. To enhance slipping between the fibers and surrounding silicone a thin layer of petroleum jelly was placed on the fibers prior to being cast in the silicone mats. The 1 mm Sorta-Clear 40 mats performed best in silicone survivability, FBG survivability and minimal impact on the BFD. The new system improves on key deficiencies that were found from inserting the fibers directly into the Kevlar with minimal to no impact on the back face deformation.

3D garment fit on solid and soft digital avatars – preliminary results

For a holistic assessment of the interaction between the human body and tight fitted clothing, it is necessary to consider the mechanical properties of the body. Default avatars in CAD software are usually solid and do not take this interaction into account. For this purpose, a solid avatar is converted to a deformable one by using the soft body physics implementation in the simulation program Blender. The fit of a 3D garment on both avatars are compared, which allows a first evaluation of the differences between these approaches.

Hydrodynamic mechanism of Misgurnus anguillicaudatus during turning maneuvers

Aquatic organisms in their natural environment have soft bodies and flexible mobility. Clarifying the generation, evolution, and dissipation of vortices and jets during turning maneuvers is crucial for understanding the propulsion principle of aquatic species, which, in turn, provides guiding value for fish-like propulsion device design. In this study, time-resolved particle image velocimetry is used to explore the kinematic and dynamic characteristics of Misgurnus anguillicaudatus while turning. The results showed that M. anguillicaudatus maintained the wavy movement of its trunk by bending different body parts. Pressure gradients that are weaker and stronger than the surrounding environment were formed at the peaks and troughs, respectively, resulting in a thrust mechanism dominated by suction. The body fluctuation and relative fluid motion served to form a vortex. The connection of the separation line of the saddle point to the focus in this process creates an unstable flow structure that accelerates vortex dissipation. Jets are formed between the reverse vortices; the thrust jets provide forward power for turning maneuvers, and the side jets provide turning torque. As the jets and tail are situated at angles to one another, only part of the jet-generated kinetic energy provides power for the fish to swim. Additionally, proper orthogonal decomposition is utilized for objectively filtering high-frequency spatial noise in complex fish wake data. The flow field reconstructed via the mode selection of an appropriate order can be used to clearly show the evolution characteristics of large-scale coherent structures.

Dynamic synthesis and transport of fluorescent substances from moulting scorpions.

Scorpion fluorescence under ultraviolet light is a well-known phenomenon, and its change is also a known biological feature during the scorpion moulting process. However, the synthesis and transport of fluorescent substances during the moulting stage remain unclear. In this study, in-depth investigations on the global fluorescence changes from the exoskeleton, fluorescence layer, coelomic fluid, and abdomen to the digestive glands indicated that the digestive glands, which occupy most of the space in the abdomen of the scorpion mesosoma segment, were responsible for synthesizing the fluorescent substances. More importantly, these fluorescent substances were produced in advance, before the moulting process, which contributed to the recovery of the fluorescent exoskeleton as early as possible. The synthesized fluorescent substances first entered the coelomic fluid, then successively passed through the inherent epithelial cell layer and two new formed endocuticle and exocuticle layers, and ultimately reached and became enriched in the new formed fluorescent layer, which was protected by the new epicuticle layer. These four new layers were the first to illustrate the structural features of the fluorescent exoskeleton. Due to the very soft body and the inability of the newly moulted scorpion to resist attacks from the predator, this special synthesis and transport strategy of the fluorescent substances could guarantee the rapid formation of the integrated fluorescent exoskeleton during the 24h after ecdysis, which would be a novel biological feature during the scorpion evolution.

Nonlinear dynamic and stability analysis of soft fluidic robotic system with reduced computational cost

The fluid-filled network of channels embedded into the soft body can be introduced as a bending actuator for the soft robot. The supporting elastic structure is deformed from the pressurized fluid into the channels. We present a strategy for solving nonlinear motion equations of a precise model at a low computational cost. The general procedure for deriving and solving equations of motion is discussed, and a semi-analytic solution is proposed. A comprehensive parameter study of selected design parameters’ influence on the actuation system is investigated, disclosing that high efficiency could be achieved at the multi-order resonances with the stability analysis.

Intrinsically Stretchable Organic Electrochemical Transistors with Rigid-Device-Benchmarkable Performance.

Intrinsically stretchable organic electrochemical transistors (OECTs) are being pursued as the next‐generation tissue‐like bioelectronic technologies to improve the interfacing with the soft human body. However, the performance of current intrinsically stretchable OECTs is far inferior to their rigid counterparts. In this work, for the first time, the authors report intrinsically stretchable OECTs with overall performance benchmarkable to conventional rigid devices. In particular, oxygen level in the stretchable substrate is revealed to have a significant impact on the on/off ratio. By employing stretchable substrates with low oxygen permeabilities, the on/off ratio is elevated from ≈10 to a record‐high value of ≈104, which is on par with a rigid OECT. The device remained functional after cyclic stretching tests. This work demonstrates that intrinsically stretchable OECTs have the potential to serve as a new building block for emerging soft bioelectronic applications such as electronic skin, soft implantables, and soft neuromorphic computing.

The Critical Role of a Backing Material in Assessing the Performance of Soft Ballistic Protection

Penetrating trauma by energised fragments is the most common injury from an explosive event. Fragment penetrations to the truncal region can result in lethal haemorrhage. Personal armour is used to mitigate ballistic threats; it comprises hard armour to protect from high-velocity bullets and soft armour to protect against energised fragments and other ballistic threats (such as from a hand gun) with low impact velocities. Current testing standards for soft armour do not focus on realistic boundary conditions, and a backing material is not always recommended. This study provides a comprehensive set of evidence to support the inclusion of a backing used in testing of soft body armour. Experiments were performed with a gas-gun system using fragment-simulating projectiles (FSPs) of different shapes and sizes to impact on a woven aramid and a knitted high-performance polyethylene ballistic fabric, with and without the ballistic gelatine soft tissue simulant as the backing material. The results showed statistically significant differences in the impact velocities at 50% risk (V50) of fabric perforation across all test configurations when the gelatine backing was used. Furthermore, the backing material enabled the collection of injury-related metrics such as V50 of tissue-simulant penetrations as well as depth of penetration against impact velocity. The normalised energy absorbed by the fabric could also be calculated when the backing material was present. This study confirms that a backing material is essential, particularly when assessing the performance of single layer fabrics against FSPs of low mass. It also demonstrates the additional benefits provided by the backing for predicting injury outcomes.

STUDY OF EFFECTIVITY Bacillus thuringiensis BASED BIO-INSECTICIDE AGAINST Oryctes rhinoceros LARVAE AT SHADE HOUSE

Oryctes rhinoceros is an important pest in oil palm plantations. Adult stage of the beetle causes damage, however larval stage is very important to be controlled to break the cycle of life. An entomopathogenic bacterium Bacillus thuringiensis is one of biological agents to control these insects. Its toxic protein content provides specific insect targets as stomach poison. Objectives of the research was to study the impact of B. thuringiensis propagated in bio-urine enriched with 5 per cent molasses towards Oryctes larvae. The research was carried out in the shade house of Plant Protection Study Program, Faculty of Agriculture, Sriwijaya University from August to November 2021. Experiment was designed in a randomized complete block design with 7 treatments and 4 replications. A total of 20 ml of bio-insecticide was dissolved in 280 ml of water, sprayed evenly on the soil mixed with male palm flowers as feed of larvae. The treatments were 6 isolates of B. thuringiensis isolated from soil in oilpalm plantation, namely with codes: C14, C15, A15, OJ, BK, and LK as well. The results showed density of B. thuringiensis spores in bio-urine media was different in each isolate. The highest spore density in isolate code LK was 4.83 x 1010 spores/ml and the lowest (in isolate A15) was at 3.5 x 1010 spores/ml. Mortality rates were significantly different between isolate treatments starting from day 3 to day 12 of observation. C15 isolate lead the highest mortality rate of 100% on day 12 while other isolates showed mortality data below 100% (88-98%). Body weight and length showed significantly differences on days 0, 6 and 12 after application. Symptoms of infection begin with a change in skin color from white to brown, dark brown and black. Death is characterized by a soft body texture and wet rot.

Lessons for Robotics From the Control Architecture of the Octopus.

Biological and artificial agents are faced with many of the same computational and mechanical problems, thus strategies evolved in the biological realm can serve as inspiration for robotic development. The octopus in particular represents an attractive model for biologically-inspired robotic design, as has been recognized for the emerging field of soft robotics. Conventional global planning-based approaches to controlling the large number of degrees of freedom in an octopus arm would be computationally intractable. Instead, the octopus appears to exploit a distributed control architecture that enables effective and computationally efficient arm control. Here we will describe the neuroanatomical organization of the octopus peripheral nervous system and discuss how this distributed neural network is specialized for effectively mediating decisions made by the central brain and the continuous actuation of limbs possessing an extremely large number of degrees of freedom. We propose top-down and bottom-up control strategies that we hypothesize the octopus employs in the control of its soft body. We suggest that these strategies can serve as useful elements in the design and development of soft-bodied robotics.

Intelligent safeguarding Leather with excellent energy absorption via the toughness-flexibility coupling designation

High-performance intelligent body armors with both soft wearability and good energy absorption are increasingly required in modern social life. Leather, a breathable, pliable, and tough natural material has extensive applications in the anti-impact field. In this study, a multifunctional Leather/CNT-SSG/PU sandwich structure with high energy absorption and excellent sensing monitoring properties is designed by integrating tough leather and flexible conductive shear stiffening gel (CNT-SSG). The maximum force dissipation capacity of the Leather/CNT-SSG/PU reaches 84 % in the drop hammer test and the limit penetration velocity up to 142.4 m/s in the ballistic test. Moreover, the Leather/CNT-SSG/PU exhibits excellent stress wave dissipation properties due to the hierarchical structure. By introducing the interdigital electrode array on the non-woven fabric layer, a bulletproof vest (Leather/CNT-SSG/NWF) with intelligent anti-impact performance and in situ monitoring behavior is successfully achieved. This toughness and flexibility coupling designation provides a novel method for next-generation soft body armor.

Cutting Simulation in Unity 3D Using Position Based Dynamics with Various Refinement Levels

Augmented and Virtual Reality-based surgical simulations have become some of the fastest-developing areas, due to the recent technological advances and changes, in surgical education. Cutting simulation is a crucial part of the virtual surgery simulation in which an incision operation is performed. It is a complex process that includes three main tasks: soft body simulation, collision detection and handling, and topological deformation of the soft body. In this paper, considering the content developer’s convenience, the deformable object simulation, using position-based dynamics (PBD), was applied in the Unity 3D environment. The proposed algorithm for fast collision detection and handling between the cutting tool and the deformable object uses a sweep surface. In case of incision, the algorithm updates the mesh topology by deleting intersected triangles, re-triangulation, and refinement. In the refinement part, the boundary edges threshold was used to match the resolution of new triangles to the existing mesh triangles. Additionally, current research is focused on triangle surface meshes, which help to reduce the computational costs of the topology modifications. It was found that the algorithm can successfully handle arbitrary cuts, keeping the framerate within interactive and, in some cases, in the real-time.

Discriminating Soft Actuators’ Thermal Stimuli and Mechanical Deformation by Hydrogel Sensors and Machine Learning

Multimodal sensing is crucial for soft robots’ environmental interaction and closed‐loop control. The sensing signals of mechanical deformation and temperature changes are often hard to differentiate manually. Herein, two hydrogel sensors are used for simultaneously proprioceptive, thermoceptive, and mechanoreceptive sensing. These stretchable sensors show high sensitivity to strain and temperature changes. Then, a machine learning model composed of a 1D convolutional neural network and a feed‐forward neural network is utilized to decode the sensing signal for various stimuli identification. It is demonstrated that the proposed method can accurately predict the soft actuator's body posture changes, such as bending, twisting, and stretching. In addition, the model can discern contact events with or without thermal stimuli. This data‐driven method for multimodal sensing discrimination might pave the way for future intelligent soft robots.