Miniature Pneumatic Curling Rubber Actuator Generating Bidirectional Motion with One Air-Supply Tube

Soft actuators driven by pneumatic pressure are promising actuators for mechanical systems in medical, biological, agriculture, welfare fields and so on, because they can ensure high safety for fragile objects from their low mechanical impedance. In this study, a new rubber pneumatic actuator made from silicone rubber was developed. Composed of one chamber and one air-supply tube, it can generate curling motion in two directions by using positive and negative pneumatic pressure. The rubber actuator, for generating bidirectional motion, was designed to achieve an efficient shape by nonlinear finite element method analysis, and was fabricated by a molding and rubber bonding process using excimer light. The fabricated actuator was able to generate curling motion in two directions successfully. The displacement and force characteristics of the actuator were measured by using a motion capture system and a load cell. As an example application of the actuator, a robotic soft hand with three actuators was constructed and its effectiveness was confirmed by experiments

Grip force measurement of soft- Actuated finger exoskeleton

Over recent years, the reseach in the field of soft actuation has been extensively increased for achieving more complex motion path with smooth, high flexible movement and high generated force at minimum operating pressure. This paper presents the study on gripping force capability of soft actuators applied on glove-type finger exoskeleton, developed in motivation to assist individuals having weak finger gripping ability in their rehabilitation exercise towards hand function restoration. The exoskeleton utilizes five cylindrical shaped pneumatic bending actuators developed in the lab, which use fiber reinforcement as a cause of bending motion that drive finger’s flexion movement. Four right-handed healthy volunteers simulated paralysis participated in the study. At 200kPa safe operating pressure, the soft exoskeleton worn by the subjects demonstrates the ability to provide adequate grip force. The grip force generated from exoskeleton worn on passive right hand is 4.66 ± 0.2 N and 3.61± 0.2 N from passive left hand, both higher than the minimum grip forces measured to hold the Hand Dynamometer of 240 g. It shows good potential to be used as a finger rehabilitation assist device

The waterbomb actuator: a new origami-based pneumatic soft muscle

This project introduces a new Pneumatic Artificial Muscle (PAM) design based on an origami structure. This artificial muscle is designed to operate at a very low range of pressures while being lightweight and compliant. It is also designed to reduce the pressure threshold and hysteresis problems present on other PAMs like the McKibben actuator. These properties are achieved thanks to a rearranging membrane based on the Waterbomb pattern, which can contract upon inflation while keeping the surface area constant. This concept has been tested using paper prototypes coated with silicone. We created thee different structures (4x8, 6x12 and 8x16 cells waterbomb actuators) from the same paper sheet (14x28cm2) and we actuated them under loads of 2, 4 and 7N. The 4x8 was discarded, but the 6x12 and 8x16 actuators contracted a maximum of 12.5% of the original length (≃10cm) while the operating pressures remained under 5Pa. We also proposed a novel approach to 3D print these actuators using a Stratasys Objet260 Connex3 3D printer. The main idea consists in creating a flat structure that can self-assemble using a technique known as 4D Printing. The pattern is printed as a flat sheet where the hinges are composites composed of an elastomeric material and shape memory polymer (SMP) fibers. These hinges can be activated through a thermomechanical process inducing a self-folding effect. Unfortunately, we were not able to verify this fabrication process due to the lack of material availability

A new fiber braided soft bending actuator for singer exoskeleton

This thesis presents a design, development and analysis of a novel bending-type pneumatic soft actuator as a drive source for a finger exoskeleton. Soft actuators are gaining momentum in robotic applications due to their simple structure, high compliance, high power-to-weight ratio and low production cost. Smaller and lighter soft actuator that can provide higher power transmission at lower operating air pressure will benefit finger actuation mechanism compared to motorized cable and pulley-driven finger rehabilitation devices. In this study, a soft actuator with new bending method is proposed. It is based on fibre reinforcement of two fibre braided angles of contraction and extension characteristics combined in a single-chamber cylindrical actuator. Another four design parameters identified that affect the bending motion and the actuating force were the air chamber diameter, position of fibre layer reinforcement, fibre reinforcement coverage angle, and silicone rubber materials. Geometrical and material parameters were varied in Finite Element Method (FEM) simulation for design optimization and some parameters were tested experimentally to validate the FEM models. The effects of fibre angles (contraction and extension) on the bending motion and force were analyzed. The optimized actuator can generate bending motion up to 131° bending angle and the end tip of the actuator can make contact with the other base tip at only 240 kPa given input pressure. Both displacement simulation and experimental testing results matched closely. Maximum bending force of 5.42 N was generated at 350 kPa. A wearable finger soft exoskeleton prototype with five optimized bending actuators was tested to drive finger flexion motion of eight healthy subjects with simulated paralysis conditions. The finger soft exoskeleton demonstrated the ability to provide gripping force of 3.61 ± 0.22 N, gained at 200 kPa given air pressure. The device can successfully provide assistance to weak fingers in gripping at least 240 g object. It shows potential in helping people with weakened finger muscle to be more independent in their finger rehabilitation exercise

Elastic Inflatable Actuators for Soft Robotic Applications

The 20th century’s robotic systems have been made out of stiff materials and much of the developments in the field have pursued ever more accurate and dynamic robots which thrive in industrial automation settings and will probably continue to do so for many decades to come. However, the 21st century’s robotic legacy may very well become that of soft robots. This emerging domain is characterized by continuous soft structures that simultaneously fulfil the role of robotic link and robotic actuator, where prime focus is on design and fabrication of the robotic hardware instead of software control to achieve a desired operation. These robots are anticipated to take a prominent role in delicate tasks where classic robots fail, such as in minimally invasive surgery, active prosthetics and automation tasks involving delicate irregular objects. Central to the development of these robots is the fabrication of soft actuators to generate movement. This paper reviews a particularly attractive type of soft actuators that are driven by pressurized fluids. These actuators have recently gained substantial traction on the one hand due to the technology push from better simulation tools and new manufacturing technologies including soft-lithography and additive manufacturing, and on the other hand by a market pull from the applications listed above. This paper provides an overview of the different advanced soft actuator configurations, their design, fabrication and applications.This research is supported by the Fund for Scientific Research-Flanders (FWO), and the European Research Council (ERC starting grant HIENA)

Elastic Inflatable Actuators for Soft Robotic Applications

The 20th century’s robotic systems have been made out of stiff materials and much of the developments in the field have pursued ever more accurate and dynamic robots which thrive in industrial automation settings and will probably continue to do so for many decades to come. However, the 21st century’s robotic legacy may very well become that of soft robots. This emerging domain is characterized by continuous soft structures that simultaneously fulfil the role of robotic link and robotic actuator, where prime focus is on design and fabrication of the robotic hardware instead of software control to achieve a desired operation. These robots are anticipated to take a prominent role in delicate tasks where classic robots fail, such as in minimally invasive surgery, active prosthetics and automation tasks involving delicate irregular objects. Central to the development of these robots is the fabrication of soft actuators to generate movement. This paper reviews a particularly attractive type of soft actuators that are driven by pressurized fluids. These actuators have recently gained substantial traction on the one hand due to the technology push from better simulation tools and new manufacturing technologies including soft-lithography and additive manufacturing, and on the other hand by a market pull from the applications listed above. This paper provides an overview of the different advanced soft actuator configurations, their design, fabrication and applications.This research is supported by the Fund for Scientific Research-Flanders (FWO), and the European Research Council (ERC starting grant HIENA)

A variable stiffness soft gripper using granular jamming and biologically inspired pneumatic muscles

As the domains in which robots operate change the objects a robot may be required to grasp and manipulate are likely to vary significantly and often. Furthermore there is increasing likelihood that in the future robots will work collaboratively alongside people. There has therefore been interest in the development of biologically inspired robot designs which take inspiration from nature. This paper presents the design and testing of a variable stiffness, three fingered soft gripper which uses pneumatic muscles to actuate the fingers and granular jamming to vary their stiffness. This gripper is able to adjust its stiffness depending upon how fragile/deformable the object being grasped is. It is also lightweight and low inertia making it better suited to operation near people. Each finger is formed from a cylindrical rubber bladder filled with a granular material. It is shown how decreasing the pressure inside the finger increases the jamming effect and raises finger stiffness. The paper shows experimentally how the finger stiffness can be increased from 21 to 71 N/m. The paper also describes the kinematics of the fingers and demonstrates how they can be position-controlled at a range of different stiffness values

Monolithic self-supportive bi-directional bending pneumatic bellows catheter

The minimally invasive surgery has proven to be advantageous over conventional open surgery in terms of reduction in recovery time, patient trauma, and overall cost of treatment. To perform a minimally invasive procedure, preliminary insertion of a flexible tube or catheter is crucial without sacrificing its ability to manoeuvre. Nevertheless, despite the vast amount of research reported on catheters, the ability to implement active catheters in the minimally invasive application is still limited. To date, active catheters are made of rigid structures constricted to the use of wires or on-board power supplies for actuation, which increases the risk of damaging the internal organs and tissues. To address this issue, an active catheter made of soft, flexible and biocompatible structure, driven via nonelectric stimulus is of utmost importance. This thesis presents the development of a novel monolithic self-supportive bi-directional bending pneumatic bellows catheter using a sacrificial molding technique. As a proof of concept, in order to understand the effects of structural parameters on the bending performance of a bellows-structured actuator, a single channel circular bellows pneumatic actuator was designed. The finite element analysis was performed in order to analyze the unidirectional bending performance, while the most optimal model was fabricated for experimental validation. Moreover, to attain biocompatibility and bidirectional bending, the novel monolithic polydimethylsiloxane (PDMS)-based dual-channel square bellows pneumatic actuator was proposed. The actuator was designed with an overall cross-sectional area of 5 x 5 mm2, while the input sequence and the number of bellows were characterized to identify their effects on the bending performance. A novel sacrificial molding technique was adopted for developing the monolithic-structured actuator, which enabled simple fabrication for complex designs. The experimental validation revealed that the actuator model with a size of5 x 5 x 68.4 mm3 i.e. having the highest number of bellows, attained optimal bi-directional bending with maximum angles of -65° and 75°, and force of 0.166 and 0.221 N under left and right channel actuation, respectively, at 100 kPa pressure. The bending performance characterization and thermal insusceptibility achieved by the developed pneumatic catheter presents a promising implementation of flexibility and thermal stability for various biomedical applications, such as dialysis and cardiac catheterization