Deflected Versus Preshaped Soft Pneumatic Actuators: A Design and Performance Analysis Toward Reliable Soft Robots.

Soft pneumatic actuators (SPAs) are customizable and conformable devices that enable desired motions in soft robots. Interactions with the environment or handling during their fabrication could introduce defects into SPAs that affect their performance. These defects could lead to high-stress concentrations in the SPA body and heterogeneous, unrepeatable, or inconsistent expansion affecting their reliability. In this work, we aim to improve the reliability of soft robots by modeling and characterizing the performance of SPAs with widely used chamber shapes and cross-sectional geometries under variable loading conditions. We also compare their capacity to provide homogeneous, repeatable, and time-wise consistent expansion with low-stress concentrations and provide a set of principles for the design of reliable SPAs. Expansion of SPAs with Straight chambers demonstrated to be more repeatable, with an average deviation of 0.06 mm and showed more than a thousand times less stress than any other chamber types. The expansion of preshaped SPAs with helical chambers showed to be up to 500% more homogeneous and 300% more efficient than their deflected counterparts. SPAs with squared cross-sectional geometries displayed more than 1000 times more time-wise consistent expansion over their circular counterparts. We conclude that SPAs that retain less potential energy or are less affected by its effects are more reliable. We derive these results into a set of principles for the design of reliable SPAs. These principles offer solutions to make informed decisions before fabrication to mitigate the most common reliability problems for SPAs and soft robots.

Flexible and Expandable Robot for Tissue Therapies - Modeling and Design.

OBJECTIVE: Implantable technologies should be mechanically compliant with the tissue in order to maximize tissue quality and reduce inflammation during tissue reconstruction. We introduce the development of a flexible and expandable implantable robotic (FEIR) device for the regenerative elongation of tubular tissue by applying controlled and precise tension to the target tissue while minimizing the forces produced on the surrounding tissue. METHODS: We introduce a theoretical framework based on iterative beam theory static analysis for the design of an expandable robot with a flexible rack. The model takes into account the geometry and mechanics of the rack to determine a trade-off between its stiffness and capability to deliver the required tissue tension force. We empirically validate this theory on the benchtop and with biological tissue. RESULTS: We show that FEIR can apply the required therapeutical forces on the tissue while reducing the amount of force it applies to the surrounding tissues as well as reducing self-damage. CONCLUSION: The study demonstrates a method to develop robots that can change size and shape to fit their dynamic environment while maintaining the precision and delicacy necessary to manipulate tissue by traction. SIGNIFICANCE: The method is relevant to designers of implantable technologies. The robot is a precursor medical device for the treatment of Long-Gap Esophageal Atresia and Short Bowel Syndrome.

Regenerative robotics.

Congenital diseases requiring reconstruction of parts of the gastrointestinal tract, skin, or bone are a challenge to alleviate especially in rapidly growing children. Novel technologies may be the answer. This article presents the state-of-art in regenerative robotic technologies, which are technologies that assist tissues and organs to regenerate using sensing and mechanotherapeutical capabilities. It addresses the challenges in the development of such technologies, among which are autonomy and fault-tolerance for long-term therapy as well as morphological conformations and compliance of such devices to adapt to gradual changes of the tissues in vivo. The potential as medical devices for delivering therapies for tissue growth and as tools for scientific exploration of regenerative mechanisms is also discussed.

In vivo tissue regeneration with robotic implants.

Robots that reside inside the body to restore or enhance biological function have long been a staple of science fiction. Creating such robotic implants poses challenges both in signaling between the implant and the biological host, as well as in implant design. To investigate these challenges, we created a robotic implant to perform in vivo tissue regeneration via mechanostimulation. The robot is designed to induce lengthening of tubular organs, such as the esophagus and intestines, by computer-controlled application of traction forces. Esophageal testing in swine demonstrates that the applied forces can induce cell proliferation and lengthening of the organ without a reduction in diameter, while the animal is awake, mobile, and able to eat normally. Such robots can serve as research tools for studying mechanotransduction-based signaling and can also be used clinically for conditions such as long-gap esophageal atresia and short bowel syndrome.

Haptic wearables as sensory replacement, sensory augmentation and trainer - a review.

Sensory impairments decrease quality of life and can slow or hinder rehabilitation. Small, computationally powerful electronics have enabled the recent development of wearable systems aimed to improve function for individuals with sensory impairments. The purpose of this review is to synthesize current haptic wearable research for clinical applications involving sensory impairments. We define haptic wearables as untethered, ungrounded body worn devices that interact with skin directly or through clothing and can be used in natural environments outside a laboratory. Results of this review are categorized by degree of sensory impairment. Total impairment, such as in an amputee, blind, or deaf individual, involves haptics acting as sensory replacement; partial impairment, as is common in rehabilitation, involves haptics as sensory augmentation; and no impairment involves haptics as trainer. This review found that wearable haptic devices improved function for a variety of clinical applications including: rehabilitation, prosthetics, vestibular loss, osteoarthritis, vision loss and hearing loss. Future haptic wearables development should focus on clinical needs, intuitive and multimodal haptic displays, low energy demands, and biomechanical compliance for long-term usage.

Design and evaluation of a multi-modal haptic skin stimulation apparatus.

Human grasping and manipulation are facilitated by cutaneous mechanoreceptors that provide information about contact location, pressure, and events such as making and breaking contact. A challenge in designing haptic feedback devices for the wearer of a prosthetic hand is simultaneous display of multiple types of haptic information. We present the preliminary design and evaluation of an apparatus for relaying multi-modal haptic information. The apparatus moves a set of contact points tangentially over the skin at a controlled speed, with controlled normal force. We apply this stimulus to an artificial skin instrumented with an embedded accelerometer, and characterize the resulting signals. Vibration frequency increases with applied normal force and tangential speed, whereas vibration amplitude increases with normal force and depends on skin properties. The results indicate that different forces and speeds can, under some conditions, be discriminated using vibration signals alone. Accurate identification of speeds is provided by series of vibration events that depend on the spatial distribution of contact points. This study motivates future work to perform human perception studies and create a wearable haptic display for prosthetics based on this concept.