assembling the wearable flexible supernumerary robotic limb and its testing with healthy volunteers

Revolutionizing Stroke Rehabilitation with Enhanced Grasping and Finger Recovery

According to previous research1, as of 2019, there were more than 100 million cases of stroke worldwide. Approximately two-thirds of these cases resulted in hemiplegic sequelae, and over 80% of severe hemiplegic stroke patients could not fully recover hand and arm function2. Furthermore, the aging population is expected to continue growing in the coming decades, leading to a significant increase in the number of potential stroke victims. The persistent upper extremity impairments following a stroke can significantly affect activities of daily living (ADLs), and hand rehabilitation has been clinically recognized as a critical objective for enhancing the activity and participation of chronic stroke patients3.
Traditional motor-driven robotic upper limb devices can provide substantial driving force, but their rigid structures often translate into large sizes and high weights. Moreover, they pose the risk of causing irreversible harm to the human body if they were to malfunction. In contrast, soft pneumatic actuators have demonstrated considerable potential in rehabilitation4, assistance5, and surgical applications6. Their advantages include safety, lightweight construction, and inherent compliance.
In recent years, numerous flexible wearable robots have emerged, designed and developed around soft pneumatic actuators. These robots have been intended for the rehabilitation and post-rehabilitation assistance of stroke patients&#39; upper limbs. They primarily encompass hand exoskeletons7,8, and supernumerary limbs9,10. Although both are used in the fields of wearable robotics and rehabilitation, the former directly interacts with the human body, potentially constraining muscles or joints, while the latter supplements the human workspace or movement without direct constraint11,12. Wearable supernumerary robotic fingers based on servo motors were developed to assist occupational therapists in activities of daily living (ADLs) training9. A similar approach can be found in other research10. These two categories of robotic fingers have introduced novel possibilities for the application of such robots in the rehabilitation assistance of hemiparetic patients. Nonetheless, it is worth noting that the rigid structure employed in these robotic designs may introduce potential considerations regarding user comfort and safety. The design, fabrication, and evaluation of a soft wearable robotic glove were presented13, which can be used for hand rehabilitation and task-specific training during functional Magnetic Resonance Imaging (fMRI). The glove utilizes soft pneumatic actuators made of silicone elastomers to generate finger joint motion, and the device is MR-compatible without causing artifacts in fMRI images. Yun et al. introduced the Exo-Glove PM, a customizable soft pneumatic assistive glove that utilizes an assembly-based approach14. This innovative design features small modules and adjustable distances between them, allowing users to customize the glove based on their phalange length using spacers. This approach maximizes comfort and performance without the need for custom manufacturing. Researchers presented soft actuators composed of elastomeric materials with integrated channels functioning as pneumatic networks15. These actuators generate bending motions that safely conform to human finger movements. Additionally, researchers introduced the AirExGlove, a lightweight and adaptable inflatable soft exoskeleton device16. This system is cost-effective, customizable for different hand sizes, and has successfully accommodated patients with varying levels of muscle spasticity. It offers a more ergonomic and flexible solution compared to rigid-linked robotic systems. While these studies have made significant contributions to the development of flexible wearable hand rehabilitation and assistive robots, it&#39;s worth noting that none of them have achieved complete portability and human-robot interaction control.
Numerous studies have explored the correlation between biological signals, such as electroencephalogram (EEG)17 or electromyogram (EMG) signals18, and human intention. However, both approaches have certain limitations within the constraints of existing devices and technological conditions. Invasive electrodes require surgical procedures on the human body, while non-invasive electrodes suffer from issues such as high noise levels and unreliability in signal acquisition. Detailed discussions of these limitations can be found in the literature19,20. Therefore, the pursuit of research into the portability and user-friendly human-machine interaction capabilities of flexible wearable supernumerary robotic limbs remains highly relevant.
In this study, a unique flexible wearable supernumerary robotic limb was designed and fabricated to assist chronic stroke patients in finger rehabilitation and gripping assistance. This robotic limb is characterized by its lightweight, safety, compliance, waterproofing, and impressive output-to-weight/pressure ratio. Two gripping modes, envelope and fingertip grasping, have been achieved while maintaining portability and ensuring a user-friendly human-robot interaction. The protocol details the design and fabrication process of the pneumatic gripper and the wearable scheme. Additionally, a human-robot interaction method based on flexible bending sensors has been proposed, allowing for convenient and user-friendly control through threshold segmentation. All these aspects have been validated through practical experiments.
The main contributions of this study are summarized as follows: (1) A lightweight, friendly, and wearable flexible supernumerary robotic limb for chronic stroke patients has been designed and fabricated. (2) A reliable method of human-robot interaction has been realized based on flexible bending sensors. (3) Real-world experiments have been conducted to verify the effectiveness and reliability of the proposed mechanism and method, which include output force testing and involve six chronic stroke patients.

Author Spotlight: Enhancing Grasping Abilities for Hemiplegic Patients with Flexible Robotic Limbs 

A Flexible Wearable Supernumerary Robotic Limb for Chronic Stroke Patients

Our research focuses on developing supernumerary robotic limbs to help hemiplegic patients with grasping movements. By employing flexible sensors, we aim to interpret patient's intentions and enable robots to perform various grasping tasks, ultimately enhancing patient's quality of life. This study introduces a novel, flexible, wearable robotic limb for chronic stroke patients.It aids finger rehabilitation and gripping, featuring lightness, safety, compliance, waterproofing, and an impressive output to weight or pressure ratio. It offers envelope and fingertip grasping modes, maintains portability, and ensures user-friendly interaction. In our upcoming research, we will primarily concentrate on the domain of human-machine interaction control, specifically in the context of grasping intent among individuals afflicted by hemiplegia.Additionally, a concrete research goal involves refining mechanical design to enhance grasping performance.

Watch this Scientific Journal Video about Assembling the Wearable Flexible Supernumerary Robotic Limb and its Testing with Healthy Volunteers at JoVE.com

Assembling the Wearable Flexible Supernumerary Robotic Limb and its Testing with Healthy Volunteers  

To begin, take the designed pneumatic gripper and secure it with 3D printed parts. Using adhesive tape, attach it to the appropriate position on the glove. Embed three flexible bending sensors into the glove.Instruct the participants to flex and extend their fingers. Use a data acquisition card to record sensor signals, amplify the sensor signals and route them to an RDU o. Now, collect data on the range and pattern of sensor changes during finger movements.Instruct participants to move their fingers freely within their range of ability. After determining the threshold, determine the appropriate time to stop inflating the air and cease further finger bending. Set the maximum air pressure for the pneumatic gripper to 100 kilo Pascals.Solicit feedback from the wearers regarding their experience. The survey of six patients showed a consensus among most participants regarding the comfort and user friendliness of the designed wearable system. Participant five provides a less favorable evaluation and raises significant concerns about the device.

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Research

JoVE Journal

Engineering

349 Views.  Huazhong University of Science and Technology. To begin, take the designed pneumatic gripper and secure it with 3D printed parts. Using adhesive tape, attach it to the appropriate position on the glove. Embed three flexible bending sensors into the glove.Instruct the participants to flex and extend their fingers. Use a data acquisition card to record sensor signals, amplify the sensor signals and route them to an RDU o. Now, collect data on the range and pattern of sensor changes during finger movements.Instruct participants...

Video: Assembling the Wearable Flexible Supernumerary Robotic Limb and its Testing with Healthy Volunteers  

In this study, we present a flexible wearable supernumerary robotic limb that helps chronic stroke patients with finger rehabilitation and grasping movements. The design of this innovative limb draws inspiration from bending pneumatic muscles and the unique characteristics of an elephant's trunk tip. It places a strong emphasis on crucial factors such as lightweight construction, safety, compliance, waterproofing, and achieving a high output-to-weight/pressure ratio. The proposed structure enables the robotic limb to perform both envelope and fingertip grasping. Human-robot interaction is facilitated through a flexible bending sensor, detecting the wearer's finger movements and connecting them to motion control via a threshold segmentation method. Additionally, the system is portable for versatile daily use. To validate the effectiveness of this innovation, real-world experiments involving six chronic stroke patients and three healthy volunteers were conducted. The feedback received through questionnaires indicates that the designed mechanism holds immense promise in assisting chronic stroke patients with their daily grasping activities, potentially improving their quality of life and rehabilitation outcomes.

This protocol introduces a flexible wearable supernumerary robotic limb tailored to assist in finger rehabilitation for stroke patients. The design incorporates a bending sensor to facilitate seamless human-robot interaction. Validation through experiments involving both healthy volunteers and stroke patients underscores the efficacy and dependability of the proposed study.

In this study, we present a flexible wearable supernumerary robotic limb that helps chronic stroke patients with finger rehabilitation and grasping ...

Designing and Fabricating the Pneumatic Gripper to Assist in Finger Rehabilitation for Stroke Patients

To begin, assemble the pre-designed mold, then use hot melt glue to secure the glass fibers at the designated positions in the mold. Weigh an appropriate amount of component A and B of the silicone elastomer and mix them in the specified ratio. Use a vacuum mixing and degassing machine with a variable centrifugal force to mix and degas the elastomer mixture.Promptly inject the mixture into the assembled mold and let it sit for approximately 30 seconds. Then place the mold in a vacuum dryer for about one minute to enable any tiny air bubbles in the silicone rubber to escape. Remove the mold from the dryer and place it in a thermostatic chamber set at 30 degrees Celsius for 12 hours.Position the demolded rubber body into the mold filled with silicone rubber. Place the entire assembly in a thermostatic chamber set at 30 degrees Celsius for 12 hours to allow the silicone rubber to cure. Remove the cured silicone rubber body from the mold and trim any excess silicone rubber.