TWIN: Lightweight Robotic Exoskeleton for the Lower Limbs
Author: Istituto Italiano di Tecnologia - IIT
Published: 23 Feb 2024 - Updated: 8 Nov 2026
Publication Type: Announcement
Table of Contents:
Synopsis - Definition - Overview - FAQs - Insights, Updates - Related Content
Synopsis
This information introduces TWIN, a powered lower-limb exoskeleton prototype presented in Milan in February 2024 by Rehab Technologies, a joint laboratory of the Italian Institute of Technology (IIT) and the Prosthetic Center of INAIL, Italy's national workplace accident insurer. Designed for people with reduced or absent leg function, such as after a complete spinal cord injury, it lets users stand, walk with crutches or a walker and sit down, with motors at the hips and knees. It is built from lightweight aluminum in modular parts with adjustable leg lengths, and a physiotherapist controls it through a tablet app using walk, retrain or TwinCare modes for different levels of impairment. The device matters to wheelchair users and rehabilitation teams because regular standing and walking can benefit muscles, bones, circulation, digestion and mood.*
At a Glance
- 1 - The battery lasts about four hours and recharges in one hour.
- 2 - TWIN is not self-balancing, so users need crutches or a walker.
- 3 - TwinCare mode supports people with one healthy leg and one leg that needs assistance.
- 4 - Testing took place at INAIL, the Montecatone Rehabilitation Institute and Villa Beretta.
Topic Definition
- Powered Exoskeleton
A powered exoskeleton is a wearable robotic frame with motors at the joints that supports and moves a person's limbs, allowing people with paralysis or weakness to stand, walk or perform tasks they could not do unaided. Lower-limb exoskeletons are used mainly in rehabilitation for spinal cord injury, stroke and other neurological conditions, and some models are approved for personal use at home and in the community.
Overview
TWIN is the name of the new robotic exoskeleton for lower limbs, designed and developed by Rehab Technologies IIT - INAIL, the joint laboratory between the Istituto Italiano di Tecnologia (IIT-Italian Institute of Technology) and the Prosthetic Center of INAIL (the prosthetic unit of the National Institute for Insurance against Accidents at Work), which will allow patients to wear it more easily. Presented in Milan during a press conference held at the Museum of Science and Technology, TWIN was demonstrated by two patients who were involved in testing the system during its development. TWIN is currently a prototype, but researchers hope to bring it to industrialization soon.
The exoskeleton TWIN originates from the IIT's Rehab Technologies Lab, which is the joint laboratory between the IIT in Genoa and the Prosthetic Center of INAIL in Budrio (Bologna), coordinated by Matteo Laffranchi. The collaboration began at the end of 2013 with the goal of developing innovative, high-tech, cost-effective solutions for patients with physical impairments.
One of the patients who wore TWIN at the presentation was Alex Santucci, who accompanied technicians and researchers throughout the entire design period of the device, participating in clinical experimentations as a tester. The clinical experiments took place not only at the Prosthetic Center of INAIL in Vigorso di Budrio but also at the Montecatone Rehabilitation Institute in Imola and at Villa Beretta in Costa Masnaga (LC).
The motorized exoskeleton TWIN is an external structure capable of enhancing the physical abilities of the wearer. It has been designed to allow individuals with reduced or even absent motor abilities in the lower limbs, such as in cases of complete spinal cord injuries, to maintain an upright position, walk with the assistance of crutches or walkers (as the exoskeleton is not self-balancing), and to stand up and sit down.
Two features make TWIN unique in the world: it is made of lightweight materials, such as aluminum alloy, and it is composed of modular components, facilitating usability and transportation. Furthermore, the structure is adjustable based on the patient's physical characteristics through telescopic links placed at the level of the femur and tibia. Ankles and foot support are available in various sizes to adapt to the ergonomics of the user, whether female or male, young or adult. TWIN's operating modes are also adaptable to the patient, evaluating the degree of motor deficit of the person wearing it, particularly their ability to perform autonomous walking.
TWIN can be controlled by an operator, such as a physiotherapist, using a specific Android application installed on the provided tablet. The graphical interface allows for controlling the exoskeleton in the execution of various programmed activities, setting the kinematic parameters of movement, and choosing between different step execution modes.
The exoskeleton works in three operating modes:
- Walk mode: Designed for patients with absent motor function, in which the exoskeleton imposes a walking pattern according to programmed parameters.
- Retrain mode: Used for patients with partial impairment of lower limb motor function, capable of performing a more or less autonomous movement but with difficulty in some phases of the step - in this case, the exoskeleton supports the patient's movement with more or less intensity, directing them towards an optimal reference trajectory.
- TwinCare mode: Designed for patients with partial and differentiated motor impairment between the two limbs, where one leg is healthy and can move autonomously, while the other requires assistance, more or less pronounced, in some phases of the step.
The TWIN motors activate the knee and hip joints, imposing a completely configurable movement pattern on the patient's limbs, in terms of step length and type, and walking speed. The battery has a lifespan of approximately four hours and requires an hour to recharge.
In addition to rehabilitation clinics during physiotherapy sessions, TWIN can be worn daily, even for just a few hours, as assuming the upright position brings significant benefits in terms of musculoskeletal, circulatory, psychological, and digestive system functionality for wheelchair users.
TWIN's next goal is CE marking, which will occur in partnership with an industrial partner, followed by the industrialization process. Once TWIN is on the market, it can be used by patients in need, reintegrating severely injured workers into social and work environments.
More on this topic: Walking Aids Publications - Mobility Aids Publications - Spinal Cord Injury Publications
Frequently Asked Questions
NOTE: Researched FAQs by Disabled World (DW)
Can exoskeletons replace wheelchairs?
Not for most people. Exoskeletons are slower, need crutches or a walker and take time to put on, so they are usually used for exercise and standing rather than everyday travel.
Who can use a lower-limb exoskeleton?
Candidates often include people with spinal cord injury, stroke or multiple sclerosis who have enough upper body strength and bone health, and who meet height and weight limits.
What are the health benefits of standing for wheelchair users?
Regular standing can help bone density, circulation, bowel and bladder function, breathing and muscle stiffness, and many users report better mood.
Are any exoskeletons approved for home use?
Yes, a few exoskeletons have been cleared in the United States and Europe for personal use, usually after training and with a trained companion present.
Does insurance cover exoskeletons?
Coverage is limited and varies by country and insurer. Some veterans and workers compensation programs have funded personal exoskeletons.
What does CE marking mean?
CE marking shows that a product meets European Union safety and performance requirements, which is needed before a medical device can be sold in the EU.
What is INAIL?
INAIL is the Italian national institute for insurance against accidents at work, which also runs a prosthetics center that develops and supplies devices for injured workers.
How long does it take to learn to walk in an exoskeleton?
Most users need several supervised sessions with a physical therapist to learn to balance, shift weight and use crutches safely in the device.
Insights, Analysis, and Developments
Editorial Note: Exoskeletons have moved from science fiction to rehabilitation gyms over the past decade, but cost, weight and setup time still keep most of them out of homes. TWIN's lightweight modular design and adjustable frame aim to make the device easier to fit, carry and share among patients, which could matter for clinics with limited budgets. As a prototype awaiting CE marking and a manufacturing partner, it is not yet available to buy, and like other exoskeletons it is meant to support standing and walking practice rather than replace a wheelchair for everyday mobility. People interested in exoskeleton therapy can ask spinal cord injury rehabilitation centers whether they offer it and who is eligible.*
Attribution/Source(s): This quality-reviewed publication was selected for publishing by the editors of Disabled World (DW) due to its relevance to the disability community. Originally issued as a press release by Istituto Italiano di Tecnologia - IIT and published on 23 Feb 2024. Last updated on 8 Nov 2026. This content may have been edited for style, clarity, or brevity.
* Editorial additions by Ian C. Langtree.