Virtual reality (VR) technology has enormous applications in education, entertainment, and healthcare. Haptic feedback can significantly enhance the immersive experience in VR. However, most commercial hand/fingertip wearable VR haptic devices rely on bulky rigid structures, which are limited in the offered stimuli and cause fatigue. This study introduces a novel soft wearable fingertip device, T-Touch, that provides both thermal and multi-frequency haptic feedback for more realistic VR experiences. A flexible electrohydraulic actuator (EHA) is adopted for multi-frequency mechanical stimuli, and a flexible thermoelectric array (Flex-TEA) is utilized for distinct thermal stimuli. The EHA and Flex-TEA can be independently controlled to activate simultaneously or independently, thereby rendering ON/OFF contact stimuli, vibrations, controlled temperature stimuli, or any combination of the three modalities. Our T-Touch device features a compact form factor of 35 mm × 25 mm × 22 mm and weighs only ∼8 g. It can generate mechanical stimuli with the maximum stroke of ∼1 mm, a force of 0.47 N, at a bandwidth >10 Hz, and can render precise thermal stimuli in the range of 20 to 40 °C. The main performance of the EHA and Flex-TEA modules is characterized in extensive experiments and the effects of the key design and actuation parameters are investigated to optimise performance. Preliminary user tests verify the efficacy of our T-Touch design in immersive VR applications.

Pouch motors continue to attract research attention owing to their simple fabrication process, low cost, and excellent energy density. Existing pouch motors based on the liquid-gas phase transition (LGPT) principle exhibit significant stroke and force outputs but suffer from slow responses. Pouch motors that rely on the electrohydraulic actuation (EHA) demonstrate rapid responses and broad bandwidths, yet their stroke/force outputs remain limited. This paper presents a novel thermal-electrostatic dual-modal soft pouch motor (TES-SPM) that synergistically combines the advantages of LGPT and EHA. The output performance of the TES-SPM in both the LGPT and EHA modes is characterized by extensive experiments. The effects of key parameters including the liquid volumes and actuation voltage/current amplitudes are also investigated in experiments. In the EHA mode, the TES-SPM can exert a stroke of 2.5 mm within a rapid ~ 0.06 s, while in the LGPT mode, it is able to exhibit a maximum stroke of 22.8 mm and a blocking force of ~ 80 N. A novel folding fan-inspired actuator and accordion-inspired soft gripper based on the serially attached TES-SPM units are developed to demonstrate the potentials of soft robotic applications. The TES-SPM designed in this paper is envisioned to have promising applications in industrial soft grippers and wearable assistive devices.

Electro-adhesive clutches have become effective tools for variable stiffness functions in many robotic systems due to their light weight, high speed and strong brake force. In this paper, we present a novel, tubular design of an electro-adhesive clutch. Our clutch consists of flexible electrode sheets rolled into a tubular structure. This design allows encapsulating large electrode areas in a compact size for strong brake force. Additionally, the tubular structure acts as a guide for directional sliding without external guides. The structure also ensures that the electrode surfaces are encapsulated, preventing the accumulation of dust and thus leading to reliable performance. This structure is therefore an improvement over the commonly used planar designs. The characterization of the electro-adhesive tubular clutch shows that the frictional force increases with the increase of the electrode contact area, the decrease of the roll diameter and the dielectric layer thickness. A retractable tubular clutch is made by fixing an elastic cable along the clutch axis and achieves a stiffness change factor up to 260. Applications of this retractable clutch in robotics to achieve variable stiffness are demonstrated in two systems: a tensegrity structure and a wing skeleton. Changes in stiffness by 13.2 and 30.2 times are achieved for the two systems, respectively. The proposed tubular clutch is an effective means of achieving variable stiffness, particularly in the case of robotic systems that transmit forces through tensioned cables.

Robots using classical control have revolutionised assembly lines where the environment and manipulated objects are restricted and predictable. However, they have proven less effective when the manipulated objects are deformable due to their complex and unpredictable behaviour. The use of tactile sensors and continuous monitoring of tactile feedback is there-fore particularly important for pick-and-place tasks using these materials. This is in part due to the need to use multiple points of contact for the manipulation of deformable objects which can result in slippage with inadequate coordination between manipulators. In this paper, continuous monitoring of tactile feedback, using a liquid metal soft force sensor, for grasping deformable objects is presented. The trained data-driven model distinguishes between successful grasps, slippage and failure during a manipulation task for multiple deformable objects. Slippage could be anticipated before failure occurred using data acquired over a 30 ms period with a greater than 95% accuracy using a random forest classifier. The results were achieved using a single sensor that can be mounted on the fingertips of existing grippers and contributes to the development of an automated pick-and-place process for deformable objects.

Handling of fabric is a crucial step in the manufacturing of garments. This task is typically performed by trained workers who manipulate one sheet at a time, thus introducing a bottleneck in the automation of the textile industry. This paper seeks to address the challenge of picking fabric up by proposing a new method of achieving ply-separation. Our approach relies on a finger-tip sized (2 cm2) electroadhesive skin to lift fabric up. A pinch-type grasp is then used to securely hold the separated sheet of fabric, enabling easy manipulation thereafter. The ability to successfully pick up and manipulate a variety of commercial fabrics with diverse materials, shapes, sizes and textures is demonstrated. The ability to handle fabrics 100s of times larger than the electroadhesive skin is unique to our approach. Additionally, we demonstrate the manipulation of non-flat fabrics, a challenge that has not been previously addressed by electroadhesive approaches. We believe that this method introduces a smarter way of handling flexible and limp materials, showing great potential towards automation of garment manufacturing.