The Soft-SixthFinger: a Wearable EMG Controlled Robotic Extra-Finger for Grasp Compensation in Chronic Stroke Patients

Abstract

This letter presents the Soft-SixthFinger, a wearable robotic extra-finger designed to be used by chronic stroke patients to compensate for the missing hand function of their paretic limb. The extra-finger is an underactuated modular structure worn on the paretic forearm by means of an elastic band. The device and the paretic hand/arm act like the two parts of a gripper working together to hold an object. The patient can control the flexion/extension of the robotic finger through the eCap, an electromyography-based (EMG) interface embedded in a cap. The user can control the device by contracting the frontalis muscle. Such contraction can be achieved simply moving his or her eyebrows upwards. The Soft-SixthFinger has been designed as tool that can be used by chronic stroke patients to compensate for grasping in many activities of daily living (ADL). It can be wrapped around the wrist and worn as a bracelet when not used. The light weight and the complete wireless connection with the EMG interface guarantee a high portability and wearability. We tested the device with qualitative experiments involving six chronic stroke patients. Results show that the proposed system significantly improves the performances of the patients in the proposed tests and, more in general, their autonomy in ADL

An EMG Interface for the Control of Motion and Compliance of a Supernumerary Robotic Finger

“…Such activities are generally bimanual tasks where one hand is used to restrain the motion of one object, while the other operates on it, e.g., unscrew the cap of a bottle, open a beans can, etc. The proposed supernumerary finger can be an effective aid in such tasks (Hussain et al, 2016). To demonstrate how the EMG interface can be used by patients, we asked to the subjects to execute different ADL involving a hold and manipulate task (see Figure 8).…”

“…In Salvietti et al (2016), we introduced an EMG interface that captures the frontalis muscle activation to control the finger flexion/extension. Finally, in Hussain et al (2016), we proposed an underactuated compliant extra finger as well as an EMG interface embedded in a cap. Concerning augmenting human healthy hand, in Prattichizzo et al (2014a), we presented a preliminary version of a robotic extra finger showing how this wearable device is able to enhance grasping capabilities and hand dexterity in healthy subjects.…”

“…In fact, while healthy subjects could potentially wear the interface on the same arm where the device is worn, patients cannot properly control hand motion and muscle contraction in their paretic upper limbs. Use the healthy arm is a possible solution as well as delocalizes the EMG reading in another part of the body, see, e.g., Hussain et al (2016). Note that the hand gestures are necessary only to select a predefined behavior of the device, so it is not necessary to keep a certain gesture for long period.…”

Playing the piano with a robotic third thumb: Assessing constraints of human augmentation

“…Robots have been used to augment the bodies of disabled humans, restoring some of their original capabilities (e.g. Aszmann et al, 2016;Hussain et al, 2016;Benabid et al, 2019;Shafti et al, 2019b). Similar setups can augment healthy users beyond their capabilities, e.g.…”

“…The introduction of supernumerary robotic fingers (SRF) developed as a grasp support device (Wu and Asada, 2014) led to further exploration on optimal materials and mechanical designs for supernumerary robotics (e.g. Hussain et al, 2016Hussain et al, , 2019Tiziani et al, 2017). SRF have been particularly envisioned, and successful in grasp restoration for stroke patients (e.g.…”