B:Ionic Glove: A Soft Smart Wearable Sensory Feedback Device for Upper Limb Robotic Prostheses

Upper limb robotic prosthetic devices currently lack adequate sensory feedback, contributing to a high rejection rate. Incorporating affective sensory feedback into these devices reduces phantom limb pain and increases control and acceptance. To address the lack of sensory feedback we present the B:Ionic glove, wearable over a robotic hand which contains sensing, computation and actuation on board. It uses shape memory alloy (SMA) actuators integrated into an armband to gently squeeze the user's arm when pressure is sensed in novel electro-fluidic fingertip sensors and decoded through soft matter logic. We found that a circular electro-fluidic sensor cavity generated the most sensitive fingertip sensor and considered a computational configuration to convey different information from robot to user. A user study was conducted to characterise the tactile interaction capabilities of the device. No significant difference was found between the skin sensitivity threshold of participants' lower and upper arm. They found it easier to distinguish stimulation locations than strengths. Finally, we demonstrate a proof-of-concept of the complete device, illustrating how it could be used to grip an object, solely from the affective tactile feedback provided by the B:Ionic glove. The B:Ionic glove is a step towards the integration of natural, soft sensory feedback into robotic prosthetic devices.</p

Characterizing Screen-printed Resistive Tactile Sensors

This bachelor’s thesis characterizes resistive tactile sensor prototypes made by master’s thesis worker Ahmed Elsayes in Tampere University biomedical engineering laboratory. He has manufactured several sensors but only one is examined in this thesis. The sensor is characterized by drawing a curve illustrating the force–resistance relationship of each element in the sensor. It includes one larger sensing element and two smaller ones that are the same size. The elements are fixed between two layers of flexible plastic film. They are connected to an electrical circuit through thin screen-printed conductors that run inside the sensor. The intention behind the tactile sensors is to create an artificial sense of touch to use in conjunction with a prosthetic hand. They could also be utilized in other flexible electronics and soft robotics applications. The sensor is used to measure the amount of force that is applied on it. The sensing elements are based on a phenomenon called piezoresistivity where a material’s electrical resistance is proportional to this force. The stress caused by the force is either compressive stress or tensile stress. However, only compressive forces are present in tactile sensing applications. The piezoresistive elements are pieces of insulating fabric doped with conducting nanoparticles. As the fabric is compressed, the distance between the particles inside the material decreases, creating a conductive path through the fabric. Thus, the fabric’s resistance diminishes. There are also other types of piezoresistive materials. Semiconductor materials, such as silicon, have been utilized in piezoresistive sensor for decades. Using a Stable Micro Systems texture analyzer, different amounts of force were exerted on the sensor. A straightforward voltage divider circuit was used to transform the change in resistance to a voltage signal. The voltage across the series resistor was input to a PC using a National Instruments DAQ device. The voltage curve was then manipulated using MATLAB and Excel to plot the final force–resistance curves. The characterized sensor indicated promising behavior. The force–resistance relationship of each piezoresistive element is logarithmic, as expected. The measurements were carried out without many errors as there was only one deviation in the data collected. The sensors seem largely suitable for the intended application. However, it was noted that when using extremely low forces, less than 0,5 N, the sensor’s output was sometimes unpredictable. Also, it was not possible to measure forces higher than 5 N with the available laboratory equipment. The results that were gathered show good promise, nonetheless. Further research is of course needed to clarify these uncertainties. The originality of this thesis has been checked using the Turnitin OriginalityCheck service

E-skin: from humanoids to humans

With robots starting to enter our lives in a number of ways (e.g., social, assistive, and surgery), the electronic skin (e-skin) is becoming increasingly important. The capability of detecting subtle pressure or temperature changes makes the e-skin an essential component of a robot's body or an artificial limb [1], [2]. This is because the tactile feedback enabled by e-skin plays a fundamental role in providing action-related information such as slip during manipulation/control tasks such as grasping, and estimation of contact parameters (e.g., force, soft contact, hardness, texture, and temperature during exploration [3]). It is critical for the safe robotic interaction - albeit as a coworker in the futuristic industry 4.0 setting or to assist the elderly at home

The SmartHand transradial prosthesis

<p>Abstract</p> <p>Background</p> <p>Prosthetic components and control interfaces for upper limb amputees have barely changed in the past 40 years. Many transradial prostheses have been developed in the past, nonetheless most of them would be inappropriate if/when a large bandwidth human-machine interface for control and perception would be available, due to either their limited (or inexistent) sensorization or limited dexterity. <it>SmartHand </it>tackles this issue as is meant to be clinically experimented in amputees employing different neuro-interfaces, in order to investigate their effectiveness. This paper presents the design and on bench evaluation of the SmartHand.</p> <p>Methods</p> <p>SmartHand design was bio-inspired in terms of its physical appearance, kinematics, sensorization, and its multilevel control system. Underactuated fingers and differential mechanisms were designed and exploited in order to fit all mechatronic components in the size and weight of a natural human hand. Its sensory system was designed with the aim of delivering significant afferent information to the user through adequate interfaces.</p> <p>Results</p> <p>SmartHand is a five fingered self-contained robotic hand, with 16 degrees of freedom, actuated by 4 motors. It integrates a bio-inspired sensory system composed of 40 proprioceptive and exteroceptive sensors and a customized embedded controller both employed for implementing automatic grasp control and for potentially delivering sensory feedback to the amputee. It is able to perform everyday grasps, count and independently point the index. The weight (530 g) and speed (closing time: 1.5 seconds) are comparable to actual commercial prostheses. It is able to lift a 10 kg suitcase; slippage tests showed that within particular friction and geometric conditions the hand is able to stably grasp up to 3.6 kg cylindrical objects.</p> <p>Conclusions</p> <p>Due to its unique embedded features and human-size, the SmartHand holds the promise to be experimentally fitted on transradial amputees and employed as a bi-directional instrument for investigating -during realistic experiments- different interfaces, control and feedback strategies in neuro-engineering studies.</p

Dexter: A Smart Prosthetic Device for Transradial Amputees

Existing prosthetics require significant user input, inhibiting device function and convenience. An assistive intelligence that could “feel” and “see” its environment, perform grasps, and provide feedback without excessive user interaction would give everyday functionality back to the wearer. This device, called Dexter, is a below-the-elbow prosthesis that can adjust its position, orientation, and grip based on visual and force feedback to detect objects and perform everyday activities. Dexter is the first intelligent anthropomorphic hand for everyday use and advanced research applications alike and provides an inexpensive, intuitive, and intelligent alternative to existing prosthetic hands

Stretchable metallization technologies for skin-like transducers

The skin is not only the largest human organ, capable of accomplishing distributed and multimodal sensing functions. Replicating the versatility of skin artificially is a significant challenge, not only in terms of signal processing but also in mechanics. Stretchable electronics are an approach designed to cover human and artificial limbs and provide wearable sensing capabilities: motion sensors distributed on the hand of neurologically impaired patients could help therapists quantify their abilities; prostheses equipped with multiple tactile sensors could enable amputees to naturally adjust their grasp force. Skin-like electronic systems have specific requirements: they must mechanically adapt to the deformations imposed by the body they equip with minimal impediment to its natural movements, while also providing sufficient electrical performance for sensor transduction and passing electrical signals and power. A metallization ensuring stable conductivity under large strains is a prerequisite to designing and assembling wearable circuits that are integrated with several types of sensors. In this work, two innovative metallization processes have been developed to enable scalable integration of multiple sensing modalities in stretchable circuits. First, stretchable micro-cracked gold (Au) thin films were interfaced with gallium indium eutectic (EGaIn) liquid metal wires. The Au films, thermally evaporated on silicone elastomer substrates, combined high sheet resistance (9 to 30 Ohm/sq) and high sensitivity to strain up to 50%. The EGaIn wires drawn using a micro-plotting setup had a low gauge factor (2) and a low sheet resistance (5 mOhm/sq). Second, a novel physical vapor deposition method to deposit of thin gallium-based biphasic (solid-liquid) films over large areas was achieved. The obtained conductors combined a low sheet resistance (0.5 Ohm/sq), a low gauge factor (~1 up to 80% strain), and a failure strain of more than 400%. They could be patterned down to 10 µm critical dimensions. Skin-like sensors for the hand were assembled using the two processes and their capabilities were demonstrated. Thin (0.5 mm) silicone strips integrating EGaIN wires and micro-cracked Au strain gauges were mounted on gloves to encode the position of a biomimetic robotic finger and a human finger. In combination with soft pressure sensors, they enabled precise grasp analysis over a limited range of motion. Then, biphasic films were micro-patterned on silicone to assemble 50 µm thin epidermal strain gauges. The strain gauges were attached on a user's finger and accurately encoded fine grasping tasks covering most of the human hand range of motion. The biphasic films were also used to power wireless MEMS pressure sensors integrated in a rubber scaffold. The device was mounted on a prosthetic hand to encode normal forces in the 0 N to 20 N range with excellent linearity. The epidermal strain sensors are currently being used to quantify the tremors of patients with Parkinson's disease. In the future, the unique properties of the biphasic films could enable advanced artificial skins integrating a high density of soft transducers and traditional high-performance circuits

On the development of a cybernetic prosthetic hand

The human hand is the end organ of the upper limb, which in humans serves the important function of prehension, as well as being an important organ for sensation and communication. It is a marvellous example of how a complex mechanism can be implemented, capable of realizing very complex and useful tasks using a very effective combination of mechanisms, sensing, actuation and control functions. In this thesis, the road towards the realization of a cybernetic hand has been presented. After a detailed analysis of the model, the human hand, a deep review of the state of the art of artificial hands has been carried out. In particular, the performance of prosthetic hands used in clinical practice has been compared with the research prototypes, both for prosthetic and for robotic applications. By following a biomechatronic approach, i.e. by comparing the characteristics of these hands with the natural model, the human hand, the limitations of current artificial devices will be put in evidence, thus outlining the design goals for a new cybernetic device. Three hand prototypes with a high number of degrees of freedom have been realized and tested: the first one uses microactuators embedded inside the structure of the fingers, and the second and third prototypes exploit the concept of microactuation in order to increase the dexterity of the hand while maintaining the simplicity for the control. In particular, a framework for the definition and realization of the closed-loop electromyographic control of these devices has been presented and implemented. The results were quite promising, putting in evidence that, in the future, there could be two different approaches for the realization of artificial devices. On one side there could be the EMG-controlled hands, with compliant fingers but only one active degree of freedom. On the other side, more performing artificial hands could be directly interfaced with the peripheral nervous system, thus establishing a bi-directional communication with the human brain

Sensors for Robotic Hands: A Survey of State of the Art

Recent decades have seen significant progress in the field of artificial hands. Most of the surveys, which try to capture the latest developments in this field, focused on actuation and control systems of these devices. In this paper, our goal is to provide a comprehensive survey of the sensors for artificial hands. In order to present the evolution of the field, we cover five year periods starting at the turn of the millennium. At each period, we present the robot hands with a focus on their sensor systems dividing them into categories, such as prosthetics, research devices, and industrial end-effectors.We also cover the sensors developed for robot hand usage in each era. Finally, the period between 2010 and 2015 introduces the reader to the state of the art and also hints to the future directions in the sensor development for artificial hands