Somatosensory, Untethered Soft Robotic Muscles.

Neural networks have been widely used in agent learning architectures; however, learning multiple context dependent tasks simultaneously or sequentially is problematic when using them. Behavioural plasticity enables humans and animals alike to respond to changes in context and environmental stimuli, without degrading learnt knowledge; this can be achieved by regulating behaviour with neuromodulation - a biological process found in the brain. We demonstrate that modulating activity-propagating signals when evolving neural networks enables agents to learn context-dependent and multi-stage tasks more easily. Further, we show that this benefit is preserved when agents occupy an environment shared with other neuromodulated agents. Additionally we show that neuromodulation helps agents that have evolved alone to adapt to changes in environmental stimuli when they continue to evolve in a shared environment.

A fluidic relaxation oscillator for reprogrammable sequential actuation in soft robots

A material that can capture changes in environmental stimuli as a color change can be used to develop sensors and displays. By producing an ordered structure in a polymer gel that reflects particular wavelengths of light, we can express the volume change that occurs based on the environment as the change in the wavelength of reflected light, i.e., structural color. To date, many systems have been developed to change the hue of the structural color as a function of temperature, pH, substance, applied force, and so on. However, as is expected from the principle of optical interference, the gel usually shows a red-shift with increasing volume. In this study, we propose a method for preparing structurally colored stimuli-responsive polymer gels that display appropriate color changes according to changes in environmental stimuli. For this purpose, we employ the photonic balls, which are spherical colloidal crystals consisting of monodisperse silica particles, as templates. By combining the wavelength-selective reflection generated from different photonic band gaps of the photonic balls, we succeeded in developing porous stimuli-responsive polymer gels that exhibited various types of color change, which are not observed in conventional systems.

Auxetics refer to a class of engineered structures which exhibit an overall negative Poisson’s ratio. These structures open up various potential opportunities in impact resistance, high energy absorption, and flexible robotics, among others. Interestingly, auxetic structures could also be tailored to provide passive adaptation to changes in environmental stimuli — an adaptation of this concept is explored in this paper in the context of designing a novel load-adaptive gripper system. Defining the design in terms of repeating parametric unit cells from which the finite structure can be synthesized presents an attractive computationally-efficient approach to designing auxetic structures. This approach also decouples the optimization cost and the size of the overall structure, and avoids the pitfalls of system-scale design e.g., via topology optimization. In this paper, a surrogate-based design optimization framework is presented to implement the concept of passively load-adaptive structures (of given outer shape) synthesized from auxetic unit cells. Open-source meshing, FEA and Bayesian Optimization tools are integrated to develop this computational framework, enhancing it adopt-ability and extensibility. Demonstration of the concept and the underlying framework is performed by designing a simplified robotic gripper, with the objective to maximize the ratio of towards-load (gripping) horizontal displacement to the load-affected vertical displacement. Optimal auxetic cell-based design generated thereof is found to be four times better in terms of exhibited contact reaction force when compared to a design obtained with topology optimization that is subjected to the same specified maximum loading.

Compared to the conventional rigid robots, the soft robots driven by soft active materials possess unique advantages with their high adaptability in field exploration and seamless interaction with human. As one type of soft robot, soft aquatic robots play important roles in the application of ocean exploration and engineering. However, the soft robots still face grand challenges, such as high mobility, environmental tolerance, and accurate control. Here, we design a soft robot with a fully integrated onboard system including power and wireless communication. Without any motor, dielectric elastomer (DE) membrane with a balloonlike shape in the soft robot can deform with large actuation, changing the total volume and buoyant force of the robot. With the help of pressure sensor, the robot can move to and stabilize at a designated depth by a closed-loop control. The performance of the robot has been investigated both experimentally and theoretically. Numerical results from the analysis agree well with the results from the experiments. The mechanisms of actuation and control may guide the further design of soft robot and smart devices.

Soft robotic devices have been utilized in a number of biomedical applications involving human interaction. An emerging opportunity for soft robotic wearable devices is in mechanotherapeutic applications for the recovery and regeneration of soft tissues. Previous studies have implied that judicious force application during mechanotherapy plays an important role in the functional outcome of tissue regeneration. In this paper, we propose soft robotic devices with closed-loop force control to precisely manipulate muscular tissue. The developed devices incorporate fully soft sensors and actuators using textile-based materials and fabrication methods. The closed-loop force control system is demonstrated in bench studies to regulate massage-magnitude forces at frequencies akin to those expected in manual mechanotherapy practices. Testing of the device on human limbs demonstrates the precision and accuracy of the closed-loop force control methodology across different body shapes and types. When commanded to regulate sinusoidal force profiles (with amplitudes of 30N, 45N and 60N), the soft robotic force control device could regulate peak compressive loads to within 0.7N of the desired force. Conversely, open-loop pressure-based control resulted in up to +/-6.6N force tracking variability between participants. A soft robotic system with independently actuatable modules was also fabricated to demonstrate force-controlled actuation patterns to mimic manual massage techniques.

Tropisms are growth-mediated plant movements that help plants to respond to changes in environmental stimuli. The availability of water and light, as well as the presence of a constant gravity vector, are all environmental stimuli that plants sense and respond to via directed growth movements (tropisms). The plant response to gravity (gravitropism) and the response to unidirectional light (phototropism) have long been shown to be interconnected growth phenomena. Here, we discuss the similarities in these two processes, as well as the known molecular mechanisms behind the tropistic responses. We also highlight research done in a microgravity environment in order to decouple two tropisms through experiments carried out in the absence of a significant unilateral gravity vector. In addition, alteration of gravity, especially the microgravity environment, and light irradiation produce important effects on meristematic cells, the undifferentiated, highly proliferating, totipotent cells which sustain plant development. Microgravity produces the disruption of meristematic competence, i.e., the decoupling of cell proliferation and cell growth, affecting the regulation of the cell cycle and ribosome biogenesis. Light irradiation, especially red light, mediated by phytochromes, has an activating effect on these processes. Phytohormones, particularly auxin, also are key mediators in these alterations. Upcoming experiments on the International Space Station will clarify some of the mechanisms and molecular players of the plant responses to these environmental signals involved in tropisms and the cell cycle.

This thesis advances the field of dielectric elastomer actuators (DEAs) through the development of device designs, fabrication processes, strain characterization technique and modelling tool. It provides the first demonstration that DEAs can be interfaced with living cells, opening the door to real-world applications in mechanobiology, an important step for the development of this emerging soft-actuator technology. It also provides a practical approach towards low voltage DEAs, demonstrating a fully-printed actuator that works below 300 V, a range compatible with commercially available CMOS circuitry, hence enabling a variety of new applications for DEA-based technologies. The mechanisms by which cells can sense and react to their mechanical environment are still partly unknown, and advances in this field will contribute to better diagnosis and treatment of serious diseases like cancer. Research heavily relies on in vitro models, and there is therefore great interests in systems capable of applying precise mechanical strain on cell cultures. This thesis overcomes the many challenges of interfacing DEAs with living cells, and presents a biocompatible device which can sustain standard cell culture protocols like sterilization, incubation, and immersion in growth medium. The device can apply from -10% to 35% uniaxial strain on a small cell population ( 100 cells), located in a transparent area (0.5mm x 1.5mm) of a larger biocompatible membrane. It can be mounted on an inverted microscope, where its novel design enables real-time high-resolution optical imaging of cells during stretching. With strain rates in the excess of 700 %/s, the in vivo environment can be reproduced with unprecedented accuracy. As a demonstration of the technology, in collaboration with the Vascular and Tumor Biology Laboratory at UNIL in Switzerland, a population of lymphatic endothelial cells (LECs) was cycled from 0% to 10% strain at 1 Hz for 24 h. The results show stretch-induced alignment of cells perpendicular to strain, and confirm that the device fringing electric field has no effect on LECs morphology. This is the first demonstration that DEAs can be interfaced with living cells, and the first time they are used to observe cell mechanosensitivity. The driving voltage of DEAs is typically in the kV range, which limits their possible applications. One approach to reduce the actuation voltage is to decrease the membrane thickness, which is typically in the 20-100 microns range, as reliable fabrication becomes challenging below this thickness. This thesis presents a pad-printed 3 microns thick DEA, and demonstrates that decreasing the membrane thickness to only a few microns significantly reduces the driving voltage, while maintaining good actuation performance. A radial strain of 7.5% was achieved at only 245 V, which corresponds to a strain-to-voltage-squared ratio of 125%/kV^2, the highest reported value to date. This thesis also investigates the electrodes stiffening impact, often overlooked in the design and development DEAs. It presents an analytical model which accounts for the electrodes stiffness, and presents a strain-mapping algorithm to compares the strain uniformity of 3 microns- and 30 microns-thick DEAs. The simulation results and the strain mapping measurements identify the electrodes as an important parameter that should not be neglected in the design and optimization of thin-DEAs.

There has been a great deal of interest in designing soft robots that can mimic a human system with haptic and proprioceptive functions. There is now a strong demand for soft robots that can sense their surroundings and functions in harsh environments. This is because the wireless sensing and actuating capabilities of these soft robots are very important for monitoring explosive gases in disaster areas and for moving through contaminated environments. To develop these wireless systems, complex electronic circuits must be integrated with various sensors and actuators. However, the conventional electronic circuits based on silicon are rigid and fragile, which can limit their reliable integration with soft robots for achieving continuous locomotion. In our study, we developed an untethered, soft robotic hand that mimics human fingers. The soft robotic fingers are composed of a thermally responsive elastomer composite that includes capsules of ethanol and liquid metals for its shape deformation through an electrothermal phase transition. And these soft actuators are integrated fully with flexible forms of heaters, with pressure, temperature, and hydrogen gas sensors, and wireless electronic circuits. Entire functions of this soft hand, including the gripping motion of soft robotic fingers and the real-time detections of tactile pressures, temperatures, and hydrogen gas concentrations, are monitored or controlled wirelessly using a smartphone. This wireless sensing and actuating system for somatosensory and respiratory functions of a soft robot provides a promising strategy for next-generation robotics.

Soft robots are a group of robots made from highly compliant materials. Compared to their rigid counterparts, soft robots show better mobility and stronger adaptability to the environment. Specifically, soft quadruped robots, using four soft actuators as robot legs, have become a popular design, and are proven to be feasible and reliable in performing soft locomotion. Traditional soft quadruped robots are actuated using pneumatic forces which require high pressure sources. Additionally, the travel range of these robots are limited. This paper proposes a new design of soft quadruped robot that is fully actuated with electric motors. The main components of the robot are 3D printed and can be easily assembled. The four soft legs of the robot are modeled with experimental data and a closed loop controller is developed to regulate the deformation and motion. The legs can perform complex movement which enables the quadruped robot to move with different gaits.

Bioinspired soft caterpillar robot with ultra-stretchable bionic sensors based on functional liquid metal

Depression and anxiety are comorbidities often associated with Parkinson disease (PD). Recent studies debate on how affective disorders can influence the cognition of patients with PD. This study sought to investigate how depression and anxiety affect specific executive functions and impulsivity traits in these patients. Twenty-eight patients with advanced PD and 28 closely matched healthy volunteers (HV) were assessed for depressive and anxiety symptoms, impulsivity, executive function and control attention and behavioral response. Compared to the HV group, the PD group showed significantly higher perseverative responses and slowness to adapt to changes in environmental stimuli and longer reaction time for inter-stimulus interval change. Depression symptoms were significantly correlated to motor impulsivity score and total Barratt Impulsiveness Scale (BIS -11) score. Moreover, there was also significant correlation between anxiety symptoms and attentional impulsivity score and total BIS-11 score. Correlation analysis between impulsivity and control attention indicated a positive correlation in commission and a negative correlation in reaction time and detectability in the PD group. The present results suggest that depression and anxiety were highly correlated to impulsivity but not to executive functions changes in these PD patients.

Background Most time series studies in air pollution epidemiology correlate absolute daily pollution concentration to health outcome without considering the time order of exposure. However, change or rate of change in exposure may be important because physiological systems often tend to respond to changes in environmental stimuli as well as absolute concentrations. This has been investigated in temperature studies but not yet for air pollution exposure. Methods Using data from London (2000-2005) and Hong Kong (2002-2008) on PM10 we computed daily changes (delta=lag1 PM10-lag0 PM10) and relative daily changes (relative delta=delta/lag1 PM10). We used Poisson generalized additive models to study associations of PM10, delta and relative delta with mortality controlling for time trend, seasonality, day of the week and weather. Results Delta for both cities and relative delta in London were negatively related with non-accidental mortality when used as single exposure metrics. For Hong Kong, excess risk (ER, with 95% CI) in non-accidental mortality for interquartile range increase in PM10 before and after controlling for delta contrasted as 1.93 (1.19, 2.68) and 2.44 (1.61, 3.28) at lag0 and 1.97 (1.23, 2.73) and 2.44 (1.61, 3.28) at lag1 respectively. But such associations were less evident for cardiovascular and respiratory causes and results were sensitive to model specification. In London, ER before and after controlling for delta compared as 0.37 (-0.04, 0.78) and 0.83 (0.37, 1.3) at lag0 and 0.91 (0.5, 1.32) and 0.83 (0.37, 1.3) at lag1 respectively. Yet delta metrics were not significant and contrary to Hong Kong, ER at lag1 declined after controlling for delta. Conclusion While the delta metrics could provide a convenient interpretation biologically, further investigations with robust modelling approaches are needed to justify discrepancies in risk estimates across different locations and mortality causes.

Morphological and/or functional char-acteristics of skeletal muscles have a greater adaptability in response to changes in environmental stimuli. For example, an atrophy associated with a shift of fiber characteristics toward fast-twitch type is a common adaptation of antigravity muscle to a microgravity environment. Neuromuscular responses and possible mechanisms of both neural and muscular adaptations to a microgravity environment are discussed in this article. Responses of morphological, metabolic, and contractile properties, as well as fiber phenotype, of muscles are briefly reviewed. Discussion is further extended to the patterns of electromyogram and tension development of muscle, responses of postural stability and locomotion, and/or motoneurons in order to study the mechanism for muscular adaptation to microgravity.

Non-communicable diseases: is their emergence in industrialized societies related to changes in neuroendocrine function?