Evaluation of a Multimodal Tactile Feedback System for Upper Limb-loss Users: Embodiment and Performance

Summary

The aim of this study is to evaluate the effect of integrating tactile feedback systems into a robotic upper-limb prosthesis. These systems deliver pressure stimuli (through small silicone chambers that inflate), vibration stimuli (through small circular actuators), or a combination of both to the arm, in order to improve the feeling of owning and controlling the artificial hand. In this way, when the robotic hand touches, grasps, and holds an object, the user receives sensory feedback that may make prosthesis use more natural, intuitive, and functional in everyday life. This is expected to improve the sense of bodily integration of the prosthesis, particularly by enhancing the perception of owning the bionic limb and the feeling of control over it, thereby improving the ability to perform daily activities with the prosthesis.

In addition, the study aims to investigate whether the simultaneous delivery of multiple stimuli may confuse or discomfort the user or they are well integrated by the sensitive system improving the experience of tactile sensation.

This is a pilot, open-label study, meaning that both the researchers and the participants will be aware of the different phases of the study. The study population will include individuals with unilateral transradial upper-limb loss, either acquired or congenital. The planned sample size is 9 participants who meet the inclusion and exclusion criteria and who provide written informed consent to take part in the study.

The study consists of two phases. Phase 1: Rubber Hand Illusion experiment During this phase, the feedback devices called WISH (pressure sensation provided by the inflation of silicone chambers), VIBES (vibration sensation), and PUSE (both devices applied and activated together to provide both sensations, either synchronously or with minimal delay) will be placed on the residual limb and secured with elastic Velcro straps. A robotic hand, controlled by the participant through electromyographic sensors, will be positioned on a table in front of the participant. The participant will see the robotic hand move while receiving sensory feedback synchronized with its movements. Different stimulation conditions (pressure only, vibration only, and combined feedback) will be tested. At the end of each condition, a questionnaire will be administered to assess the perception of ownership and agency.

Phase 2: Upper-limb prosthesis use In the second phase, the actuators will be integrated into the socket of a SoftHand robotic prosthesis, a myoelectric upper-limb prosthesis. Participants will be asked to wear the prosthesis and perform tasks under each of the feedback conditions tested in Phase 1. After a free-use familiarization period of approximately 10 minutes, participants will be asked to perform tasks involving object and surface recognition, as well as activities of daily living, which will be timed. The results of the different conditions will be compared to identify the feedback configuration associated with the best performance, defined as fewer errors and shorter execution time. At the end of each condition, a questionnaire will be administered to assess ease of use and tolerability of the prosthesis.

Conditions

• Amputees

Interventions

DEVICE

Pressure and vibrotactile feedbak

In this arm we will test the combination of a pressure and a vibrotactile feedback. The Prosthetic Upper Limb Sensory Enhancement (PULSE) device is a dual-feedback system, combining both the VIBES and WISH devices. It includes two silicone chambers (WISH) to transmit pressure stimuli related to grip force and two vibrotactile motors (VIBES) to provide high-frequency stimuli capable of conveying surface contact and texture signals. The subject will undergo a rubber hand illusion task, recognition task and daily live activity performance wearing the PULSE device.

DEVICE

Pressure feedback

The feedback configuration tested in this arm will give a pressure resembling the grip force of the robotic hand. The Wearable Integrated Soft Haptic (WISH) is a pneumatic device acting as a force feedback system, capable of transmitting pressure information related to the grip force of a robotic hand during grasping actions.

DEVICE

Vibrotactile feedback

We will evaluate the Vibro-Inertial Bionic Enhancement System (VIBES). This device can convert acceleration information from Inertial Measurement Units (IMUs) into vibratory stimuli that can be associated with texture and first contact with an object. The subject will undergo a rubber hand illusion task, recognition task and daily live activity performance wearing the VIBES device.

Sponsors & Collaborators

• University of Pisa

  lead OTHER

Study Design

Allocation

RANDOMIZED

Purpose

DEVICE_FEASIBILITY

Masking

NONE

Model

CROSSOVER

Eligibility

Min Age

18 Years

Max Age

80 Years

Sex

ALL

Healthy Volunteers

No

Timeline & Regulatory

Start

2026-01-09

Primary Completion

2026-08-31

Completion

2026-12-31

Countries

• Italy

Study Locations