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In this work, the design and the experimental characterization of a soft gripper which takes inspiration from the octopus tentacle is presented. The system is a single silicone–based pneumatic soft actuator which is able to perform bending motion thanks to its particular geometry and, due to the presence of an embedded suction cup, it can provide enhanced adhesion to the object surface of the goods to be grasped. Firstly, the design aspects as well as the fabrication process of the single-tentacle soft gripper are described. Then, its performances in terms of bending behavior, static deflection, shape variation under applied load and detachment force of the suction cup are evaluated. The experiments include grasping tests of spherical payloads with di ff erent weights. This gripper might have impact in the grasping and manipulation of delicate products like mozzarella in the agrifood field. [ABSTRACT FROM AUTHOR]

The growing need for manipulators capable of handling delicate objects with care and coexisting safely with humans has brought soft robots to the forefront as a practical and cost-effective solution. In this context, this paper aims to explore soft grippers, a unique and versatile subset of soft robots. It provides an overview of various soft grasping techniques and materials, highlighting their respective advantages and limitations, along with showcasing several designed and tested models. As medicine and agriculture are acknowledged as pivotal domains required for basic human survival, this paper explores the potential applications of soft robotic grippers in these respective fields. Additionally, it further investigates how soft grippers can contribute to reducing cost and enhancing production efficiency while addressing practical relevant solutions. Considering the escalating environmental threats, particularly in oceans and coral reefs, the paper examines the potential of soft grasping underwater to mitigate these challenges, considered as crucial for conserving the fisheries industry and pertinent economic fields. Lastly, it outlines the current challenges and future prospects of soft grippers, emphasizing the importance of overcoming obstacles through finding solutions such as using bioinspiration to create effective technical solutions and highlighting the importance of commercialization. [Display omitted] [ABSTRACT FROM AUTHOR]

Facing increasingly complex on-orbit servicing missions, soft grippers and manipulators are showing favorable opportunity to capture and manipulate targets safely. Among multiple soft-gripper actuation techniques, the dielectric elastomer actuator (DEA) shows superior application prospects for on-orbit missions as it can directly respond to voltage stimulation. However, small load capacity limits the further practical use of DE grippers. In this paper, a novel design of dielectric elastomer tridimensional minimum energy structure (DE-TriMES) along with its analytical model are proposed. This DE-TriMES design features pre-stretched DE film and elastic frame positioned in different planes. Analytical model points out that, by elevating the DE film from the elastic frame, DE-TriMES can effectively enhance its load capacity along with the tip stroke. Both multiphysics finite element simulation and experimental tests are carried out to verify the design and its model. Considering the space environment constraints, fabrication scheme of DE-TriMES finger prototypes is carefully decided. Conductive silicone and screen-printing technique are utilized to form thin and steady electrodes and selective laser sintering (SLS) technique is utilized to realized complicate but unimorph frame. The experiments verifies that this design can lead to high load capacity and outstanding specific force output, which indicates a favorable vision for further developing tridimensional DEMES design. [Display omitted] • A novel DE-TriMES design that can greatly magnify both blocked force and free motion is proposed. • Analytical model explaining the magnification effect is framed and validated by both FEM and experiments. • New fabrication techniques that enable more complex but reliable DEMES design is also proposed. [ABSTRACT FROM AUTHOR]

In this paper, a purely data-driven modelling approach is presented for predicting and controlling the free bending angle response of a typical soft pneumatic actuator (SPA), embedded with a resistive flex sensor. An experimental setup was constructed to test the SPA at different input pressure values and orientations, while recording the resulting feedback from the embedded flex sensor and on-board pressure sensor. A calibrated high speed camera captures image frames during the actuation, which are then analysed using an image processing program to calculate the actual bending angle and synchronise it with the recorded sensory feedback. Empirical models were derived based on the generated experimental data using two common data-driven modelling techniques; regression analysis and artificial neural networks. Both techniques were validated using a new dataset at untrained operating conditions to evaluate their prediction accuracy. Furthermore, the derived empirical model was used as part of a closed-loop PID controller to estimate and control the bending angle of the tested SPA based on the real-time sensory feedback generated. The tuned PID controller allowed the bending SPA to accurately follow stepped and sinusoidal reference signals, even in the presence of pressure leaks in the pneumatic supply. This work demonstrates how purely data-driven models can be effectively used in controlling the bending of SPAs under different operating conditions, avoiding the need for complex analytical modelling and material characterisation. Ultimately, the aim is to create more controllable soft grippers based on such SPAs with embedded sensing capabilities, to be used in applications requiring both a ‘soft touch’ as well as a more controllable object manipulation. [ABSTRACT FROM AUTHOR]

Harvesting fruits and vegetables is a complex task worth to be fully automated with robotic systems. It involves several precision tasks that have to be performed with accuracy and the appropriate amount of force. Classical mechanical grippers, due to the complex control and stiffness, cannot always be used to harvest fruits and vegetables. Instead, the use of soft materials could provide a visible advancement. In this work, we propose a soft, sensorized gripper for harvesting applications. The sensing is performed by tracking a set of markers integrated into the soft part of the gripper. Different machine learning-based approaches have been used to map the markers' position and dimensions into forces in order to perform a close-loop control of the gripper. Results show that force can be measured with an error of 2.6% in a range from 0 to 4 N. The gripper was integrated into a robotic arm having an external vision system used to detect plants and fruits (strawberries in our case scenario). As a proof of concept, we evaluated the performance of the robotic system in a laboratory scenario. Plant and fruit identification reached a positive rate of 98.2% and 92.4%, respectively, while the correct picking of the fruits, by removing it from the stalk without a direct cut, achieved an 82% of successful rate. [Display omitted] • A soft, sensorized gripper for delicate but precise picking. • Each sensing unit contains a patterned, soft hemisphere and an RGB camera. • Forces estimated using K-Neighbor Regression using the deformed patterned data. • Integration with a robotic arm and external vision system to estimate the position and ripeness of the fruits. • The picking is controlled in a close-loop using the sensor data. [ABSTRACT FROM AUTHOR]

As a heat-triggered smart material, shape memory alloy (SMA) has been widely used in soft actuators and bioinspired robots. Coupled SMA wires are commonly chosen to achieve reversible actuation, while segment assembling methods are the main solutions for complicated bending modes. To address this, dual-stimulus responsive SMA/PDMS soft actuators were proposed in this research. As exerted by electrical current, the SMA/PDMS actuators showed a reversible bending process, which was beneficial for elastic energy storage and the release effect of PDMS elastomers wrapped around one-way shape memory SMA wires. The optimization of the current intensity and the PDMS thickness could be used to control bending amplitude, response time, and deformation recovery. This provided a reversible actuation manner with only single SMA wires instead of coupled SMA wire arrangements. In addition, photomechanical bending could be observed as the SMA/PDMA actuators were stimulated by near-infrared (nIR) light, which could be attributed to the localized photothermal effect of the SMA wires with nIR light illumination. Localized and continuous deformations were obtained that were dependent on the light intensity and the PDMS thickness and width. This demonstrated the ease of control that was beneficial with only a light stimulus instead of commonly utilized segment assembling. Two kinds of SMA/PDMS actuator-based soft grippers were used to grasp different shaped objects. Grasping and release actions could be achieved in electrically actuated conditions, while conformal grasping functions could be achieved as the light source illuminated. Our proposed SMA/PDMS actuators show potential applications in bioinspired soft hands and expand soft robots application areas. [Display omitted] • Dual-stimulus responsive SMA/PDMS soft actuators were fabricated with help of 3D printing. • Soft actuators showed electrically reversible bending tuned by optimizing current intensity and PDMS thickness. • Localized photomechanical deformation was enabled and dependent on light intensity, PDMS thickness and width. • Grasping-release was achieved in electrically-actuated gripper, while conformal grasping as nIR illuminated. [ABSTRACT FROM AUTHOR]

• First attempts to automatically control the deformation of SMA-based soft gripper. • Establishing a closed-loop PID control system with a camera as a vision sensor to detect and control the bending deformation of the soft finger in real-time. • Utilizing a SMA-based soft planar gripper with the desired deformation to successfully grip deformable objects. Integrating flexible sensors into a soft finger is a common approach to control the deformation of the finger. However, adding sensors, especially sensors with a degree of stiffness, sacrifices the overall compliance of the finger structure and increases the complexity of fabrication and control. This study provides an alternative approach, without the need for integrated sensors, to control the deformation of a shape memory alloy (SMA)-based soft planar gripper for grasping deformable objects. The gripper consists of one soft finger which is an SMA-based hinge actuator capable of producing hinge-like bending deformation. The soft finger can automatically achieve the desired deformation by introducing a closed-loop PID control system. A camera as a vision sensor, instead of integrated flexible sensors, was used to detect the bending deformation of the soft finger in real-time. With the feedback from the camera, the PID controller was implemented in a microcontroller with designed external circuits, to enable the soft finger to reach any targeted bending angle within its deformation range, according to the size of the manipulated object. As a demonstration, the soft planar grippers with the desired deformation were eventually used to grip deformable objects, including flowers and a panicle. Without the need for material characterization and analytical models, the proposed method can also be extended to other soft planar grippers based on different actuation techniques. Successful manipulation is demonstrated using the SMA-based soft planar grippers with the desired deformation to grip the delicate and deformable objects, including flowers and a panicle. Image, graphical abstract [ABSTRACT FROM AUTHOR]