The present project has a specific focus on expanding the current knowledge and enhancing technique about 3D-printed sensors with many potential applications. Neuro-muscular diseases cause motor impairment in subjects with different level of severity. Rehabilitation plays a fundamental role in the treatment. In the last decade, exoskeleton solutions were introduced. Currently their application is not so widespread because of their weight, design and assembly complexity, and high cost. Effective improvements could be obtained through new emerging paradigms such as soft robotics and lightweight exoskeletons. The soft and sensing 3D printed exoskeleton with embedded force sensors, proposed in this project, will represent the groundbreaking approach to design a new generation of wearable robotic devices.
Beside the application in soft robotics, the recent development of soft and bio-compatible materials for 3D-printing, opens to an unprecedented scenario where implantable motion sensors could be manufactured in a few hours and in a single piece. This could finally put together the characteristics of biocompatibility and high compliance needed for implantable devices, with the advantages of 3D-printing, paving the way for the future approach to neuromuscular disease treatments.
Recent developments in artificial neural networks could help in designing algorithms trained on the specific sensor output, for filtering the sensor signal and generating a linearized output, capable also to compensate for hysteresis and anisotropy, improving the metrological characteristics of the solution.
Although in the last decade robotic technologies have changed the paradigms of rehabilitation, enhancing the traditional physiotherapy by introducing a tool for a more accurate and reproducible physical exercise, several disadvantages have been reported. Old-fashioned robotic exoskeletons were designed with rigid metal links, heavy batteries, and servomotors to deliver high forces and torques to the human joints and limbs of the wearer. However, the biggest drawbacks of using exoskeleton face with the high cost of product marketing. Currently, due to the expensive costs of a commercial exoskeleton, that can reach $100,000 for complex exoskeleton such as Ekso or Argo Medical Technology, the application of rehabilitation training with those technologies are limited to clinics and hospitals. Moreover, the significant inertia, the need for a perfect alignment between human and robot joints, the increased mechanical complexity and heaviness along with the strong cosmetic impact discourage the use of such robotics in daily living.
Besides, traditional exoskeleton technology has shown promising results only in those populations, such as paraplegics, where there is no longer the capability to walk autonomously. Conversely, in neuromuscular disorders such as Parkinson¿s disease in which patients maintain some capability to walk independently on their own, the rigid nature of most robotics could adversely affect both kinematics, stability, rhythmicity, and movement expenditure as they can restrict natural movements. The recent developments in soft materials and in Additive Manufacturing processes allow the design of wearable robotics with a wide spectrum of benefits such as lightweight, low-profile, and lower cost.
Despite the 3D printed sensors build-in soft exoskeletons are still a proof of concept in the electrical and mechanical measuring field, the embedded technologies could provide capabilities that go far beyond those provided by commercial off-the-shelf sensors. The novel cutting edge technologies able to produce a ¿sensing¿ structure by a single manufacturing process will shorten production times and facilitate complex designing as per soft robotics exoskeleton. These manufacturing methods are based on melting and solidification procedures that lead to the production of a solid component with different mechanical properties and high dimensional accuracy. Geometrically compound parts, with various inner shapes and sizing, can be quickly realized with those promising technologies overcoming limitations of traditional manufacturing fabrications. The manufacture of various mechanical parts, such as electronic components and sensors, with these novel techniques, could enable measurements of different physical parameters such as force, pressures, displacements, and strain. In this context, the newly developed soft robotics made of sensing technologies highly flexible and unobtrusive will be the starting point for the 3D printed sensors application.
Regarding the implantable version of the 3D-printed sensors, the innovative and revolutionary aspect is even higher. The use of implantable devices in medicine is a reality that does not benefit all disease typologies. Prosthesis for bones, joints, cardiac valves, auditory system, as well as auxiliary devices as pacemakers or deep brain stimulators make living possible for a large pathologic population. Motor impairment, due to neuromuscular diseases, instead is tackled, as of today, by technology, only through external solutions, such as exoskeletons, as replacing or assistive devices for ¿internal¿ motor control has been long deemed too difficult and ambitious. The shifting of paradigm, from external to internal bioengineering implies the development of completely novel versions of ¿hardware¿. New implantable stimulators and/or actuators and, new implantable sensors. The development of such a technology will inform and inspire scientists and researchers to move towards the novel approach when dealing with a neuromuscular pathology, fueling the development of neural-inspired models, which, as a secondary outcome, will contribute to shed light on functioning of different areas of the brain.