Soft Actuators and Robotic Devices for Rehabilitation and Assistance

Soft actuators and robotic devices have been increasingly applied to the field of rehabilitation and assistance, where safe human and machine interaction is of particular importance. Compared with their widely used rigid counterparts, soft actuators and robotic devices can provide a range of significant advantages; these include safe interaction, a range of complex motions, ease of fabrication and resilience to a variety of environments. In recent decades, significant effort has been invested in the development of soft rehabilitation and assistive devices for improving a range of medical treatments and quality of life. This review provides an overview of the current state-of-the-art in soft actuators and robotic devices for rehabilitation and assistance, in particular systems that achieve actuation by pneumatic and hydraulic fluid-power, electrical motors, chemical reactions and soft active materials such as dielectric elastomers, shape memory alloys, magnetoactive elastomers, liquid crystal elastomers and piezoelectric materials. Current research on soft rehabilitation and assistive devices is in its infancy, and new device designs and control strategies for improved performance and safe human-machine interaction are identified as particularly untapped areas of research. Finally, insights into future research directions are outlined

Soft Actuators and Robotic Devices for Rehabilitation and Assistance

Soft actuators and robotic devices have been increasingly applied to the field of rehabilitation and assistance, where safe human and machine interaction is of particular importance. Compared with their widely used rigid counterparts, soft actuators and robotic devices can provide a range of significant advantages; these include safe interaction, a range of complex motions, ease of fabrication and resilience to a variety of environments. In recent decades, significant effort has been invested in the development of soft rehabilitation and assistive devices for improving a range of medical treatments and quality of life. This review provides an overview of the current state-of-the-art in soft actuators and robotic devices for rehabilitation and assistance, in particular systems that achieve actuation by pneumatic and hydraulic fluid-power, electrical motors, chemical reactions and soft active materials such as dielectric elastomers, shape memory alloys, magnetoactive elastomers, liquid crystal elastomers and piezoelectric materials. Current research on soft rehabilitation and assistive devices is in its infancy, and new device designs and control strategies for improved performance and safe human-machine interaction are identified as particularly untapped areas of research. Finally, insights into future research directions are outlined

Design, modeling and control of a soft gripper with TCP actuator using image processing

Artificial muscles have gained importance due to their high deformability, which is used in soft robots. In this article, to further exploit and understand the behavior of TCP muscles, as well as to control these muscles more easily, we mathematically model the stimulus, which includes a model to understand the temperature behavior of muscles with changes in flow and amount of displacement due to changes in temperature and amount of external force. is. By designing a soft gripper and applying the necessary restrictions, we get the force needed to move this gripper. Then we obtain the inematic model of the finger to obtain the bending angle due to the displacement of the muscle which is connected to the fingers and gripper by the cable. We also check the muscle's ability to perform this movement. In the next step, programming and implementation of a simple model of turning on and off the heating and cooling system to create expansion and contraction in the muscle is done by image processing on the Arduino controller to control the system. Using the obtained models and taking into account different and important values in the models, we extracted the related diagrams and checked and compared them. From these results, we can point out the changes in the temperature behavior and movement of the muscle with the change in the input current as well as the type of alloy used, the controllability of the muscle, and the ability of the muscle to move the gripper

Compliant, Large-Strain, and Self-Sensing Twisted String Actuators with Applications to Soft Robots

The twisted string actuator (TSA) is a rotary-to-linear transmission system that has been implemented in robots for high force output and efficiency. The basic components of a TSA are a motor, strings, and a load (to keep the strings in tension). The twisting of the strings shortens their length to generate linear contraction. Due to their high force output, energy efficiency, and compact form factor, TSAs hold the potential to improve the performance of soft robots. Currently, it is challenging to realize high-performance soft robots because many existing soft or compliant actuators exhibit limitations such as fabrication complexity, high power consumption, slow actuation, or low force generation. The applications of TSAs in soft robots have hitherto been limited, mainly for two reasons. Firstly, the conventional strings of TSAs are stiff and strong, but not compliant. Secondly, precise control of TSAs predominantly relies on external position or force sensors. For these reasons, TSA-driven robots are often rigid or bulky.To make TSAs more suitable for actuating soft robots, compliant, large-strain, and self-sensing TSAs are developed and applied to various soft robots in this work. The design was realized by replacing conventional inelastic strings with compliant, thermally-activated, and conductive supercoiled polymer (SCP) strings. Self-sensing was realized by correlating the electrical resistance of the strings with their length. Large strains are realized by heating the strings in addition to twisting them. The quasi-static actuation and self-sensing properties are accurately captured by Preisach hysteresis operators. Next, a data-driven mathematical model was proposed and experimentally validated to capture the transient decay, creep, and hysteretic effects in the electrical resistance. This model was then used to predict the length of the TSA, given its resistance. Furthermore, three TSA-driven soft robots were designed and fabricated: a three-fingered gripper, a soft manipulator, and an anthropomorphic gripper. For the three-fingered gripper, its fingers were compliant and designed to exploit the Fin Ray Effect for improved grasping. The soft manipulator was driven by three TSAs that allowed it to bend with arbitrary magnitude and direction. A physics-based modeling strategy was developed to predict this multi-degree-of-freedom motion. The proposed modeling approaches were experimentally verified to be effective. For example, the proposed model predicted bending angle and bending velocity with mean errors of 1.58 degrees (2.63%) and 0.405 degrees/sec (4.31%), respectively. The anthropomorphic gripper contained 11 TSAs; two TSAs were embedded in each of the four fingers and three TSAs were embedded in the thumb. Furthermore, the anthropomorphic gripper achieved tunable stiffness and a wide range of grasps

Design, characterisation and control of TCN artificial muscles

Today there are several muscle weaknesses that hinder individuals from fully using their mobility. In attempts to solve these problems, several artificial muscles, so called actuators, have been invented to complement skeletal muscles. Yet, there is not a single actuator that covers all the characteristics of such muscles. In recent years, a new way of manufacturing actuators has made its way into the field. The actuators are manufactured by twisting and coiling silver coated nylon yarn and activated by sending a voltage through them. This thesis covers research on the design, characterisation and control of Twisted and Coiled Nylon (TCN) actuators. It explains the manufacturing process, including the yarn to use, the number of twists to perform for the thread to coil and how to handle the coiled thread. It also describes how to manufacture a longer actuator. The characterisation and control are studied through testing the actuators with a control program written in MATLAB and comparing their behaviour due to several PID parameters together with a bilinear compensation and displacement reference. The project also includes an introduction to a rigidifiable material where the actuators are applied to change the rigidity of a flexible material. In conclusion, the result of the study of the design, characterisation and control shows that the material used, Shieldex® 235/36 dtex 2-ply HCB, does not reach new heights in the research on TCN actuators due to its force-to-strain ratio being lower than the ratio of previously obtained actuators. The actuators can still be used in the rigidifiable material, which gives them a future chance.Ingeniería Biomédic

Automated Sensing Methods in Soft Stretchable Sensors for Soft Robotic Gripper

A soft robot is made from deformable and flexible materials such as silicone, rubber, polymers, etc. Soft robotics is a rapidly evolving field where the human-robot-interaction and bio-inspired design align. The physical characteristics such as highly deformable material and dexterity make soft robots widely applicable. A soft robotic gripper is a robotic hand that acts like a human hand and grasps any object. The most common applications of soft robotics grippers are gripping and locomotion in sensitive applications where high dynamic and sensitivity are essential. Nowadays, soft robotics grippers are used without any sensing method and feedback as it is crucial to make the output feedback from the gripper. The major drawback of soft robotic grippers is their need for more precision sensing. In traditional robots, we can integrate any sensor to detect the force and orientation of objects. Still, soft robotic grippers rely on the deformation sensing method, where the sensor must be highly flexible and deformable. With a precise sensing method, it is easier to determine the exact position or orientation of the object being gripped, and it limits the application of the soft robotic gripper. Sometimes, soft robots are employed in harsh environments to solve problems. With the sensing feedback, automation may become more reliable and succeed altogether. So, in this research, we have designed and fabricated a soft sensor to integrate with the gripper and to observe the feedback of the gripper. We propose integrated multimodal sensing that incorporates applied pressure and resistance change. The sensor provides feedback when the grippers hold any object, and the output response is the resistance change of the sensor. The liquid metal is susceptible and can respond to low force levels. We presented the 3D design, FEM simulation, fabrication, and integration of the gripper and sensor, and by showing both simulation and experimental results, the gripper is validated for real-time application. FEM simulation simulates behavior, optimizing design and predicting performance. We have designed and fabricated a soft sensor that yields microfluidic channel arrays embedded with liquid metal Galinstan alloy and a soft robotic gripper hand. Different printing processes and characterization results are presented for the sensor and actuator. The fabrication process of the gripper and sensor is adequately described. The gripper output characteristics are tested for bending angle, load test, elongation, and object holding under various applied pressure. Additionally, the sensor was tested for stretchability, linearity and durability, and human gesture integration with the finger, and this sensor can be easily reused/ reproduced. Furthermore, the sensor exhibits good sensitivity concerning different pressure and grasping various objects. Finally, we collected data using this sensor-integrated gripper and trained the dataset using machine learning models for automation. With more data, this can be an autonomous gripper with intelligent sensing methodologies. Moreover, this proposed stretchable sensor can be integrated into any existing gripper for innovative real-time applications

Characterizing material properties of drawn monofilament for Twisted Polymer Actuation

The field of smart materials has experienced a significant growth in the past fifteen years in actuation applications due to their smart and adaptive capabilities. However, most of these smart materials share the drawback of high cost, making their development and implementation difficult. This limitation leads us to the study of Twisted Polymer Actuators (TPAs). TPAs are inexpensive drawn monofilaments of polymers, such as fishing line, capable of actuation under thermal loads. The actuation on TPAs is due to the anisotropic thermal expansion responses of the material in the radial and axial directions. The properties of the precursor monofilament can be used to predict the actuation of TPAs. This thesis focuses on characterizing the mechanical and thermal properties of the precursor monofilament necessary as input parameters for actuation models. The properties obtained in this thesis are: axial modulus, shear modulus, radial modulus, Poisson's ratio, axial thermal contraction, and radial thermal expansion. The mechanical properties are presented as a function of temperature under the assumption of linear elasticity, but also as a function of time to characterize the viscoelastic effect at room temperature. The thermal expansion properties are also presented as functions of temperature and time, and it is found that viscous effects on thermal properties can be ignored for rapid actuation periods. Finally, this thesis presents experimental actuation data for different test conditions: free torsional actuation and torsional actuation under an isotonic torsional load. In the latter, actuation is performed for two different configurations: single monofilament and a triple strand in parallel arrangement

4D printing roadmap

Four-dimensional (4D) printing is an advanced manufacturing technology that has rapidly emerged as a transformative tool with the capacity to reshape various research domains and industries. Distinguished by its integration of time as a dimension, 4D printing allows objects to dynamically respond to external stimuli, setting it apart from conventional 3D printing. This roadmap has been devised, by contributions of 44 active researchers in this field from 32 affiliations world-wide, to navigate the swiftly evolving landscape of 4D printing, consolidating recent advancements and making them accessible to experts across diverse fields, ranging from biomedicine to aerospace, textiles to electronics. The roadmap’s goal is to empower both experts and enthusiasts, facilitating the exploitation of 4D printing’s transformative potential to create intelligent, adaptive objects that are not only feasible but readily attainable. By addressing current and future challenges and proposing advancements in science and technology, it sets the stage for revolutionary progress in numerous industries, positioning 4D printing as a transformative tool for the future

Biomimetic Based Applications

The interaction between cells, tissues and biomaterial surfaces are the highlights of the book "Biomimetic Based Applications". In this regard the effect of nanostructures and nanotopographies and their effect on the development of a new generation of biomaterials including advanced multifunctional scaffolds for tissue engineering are discussed. The 2 volumes contain articles that cover a wide spectrum of subject matter such as different aspects of the development of scaffolds and coatings with enhanced performance and bioactivity, including investigations of material surface-cell interactions