A wearable skin stretch haptic feedback device: Towards improving balance control in lower limb amputees

Biomechanically-Consistent Skin Stretch as an Intuitive Mechanism for Sensory Feedback: A Preliminary Investigation in the Lower Limb

The proprioceptive loss accompanied by lower limb amputation can impair function and mobility. We explore a simple, mechanical skin-stretch array configured to generate superficial tissue behaviour that might occur with movement about an intact joint. Four adhesive pads attached around the circumference of the lower leg were connected via cords to a remote "foot" mounted on a ball joint attached to the underside of a fracture boot, such that "foot" reorientation would result in skin stretch. In two discrimination experiments performed with and without the connection, with no view of the mechanism, and with minimal training, unimpaired adults (i) estimated foot orientation following passive foot rotations (eight directions), either with or without contact between the lower leg and boot, and (ii) actively lowered the "foot" to estimate slope orientation (four directions). In (i), 56-60% of responses (depending on contact condition) were correct and 88-94% were either correct or one of the two adjacent choices. In (ii), 56% of responses were correct. In contrast, without the connection, participants performed near or no different to chance. A biomechanically-consistent skin stretch array may be an intuitive means to convey proprioceptive information from an artificial or poorly innervated joint.

HapticLink: A Force-based Haptic Feedback System for Single and Double Lower-Limb Amputees

Lower limb amputation affects an estimated 1.71 million people in the US. The lack of sensory feedback and proprioception often causes loss of balance which heightens the risk of falls and injury. In this presented paper, a haptic feedback system named HapticLink was developed based on the weight distribution of the prosthetic foot to increase the individual's balance and the self-attribution of the prosthesis. The repeatability and linearity of four different force sensors were tested. The FlexiForce A201 sensors were identified as the optimal choice for the parameters and scenarios investigated. HapticLink consists of four A201 sensors, a microcontroller, and four Vibration Motors (VM). The developed system can determine and convey weight distribution on a prosthetic foot to the wearer as haptic feedback. Initial tests with Lower-Limb Prosthetic (LLP) users were conducted with quantitative results (Directional, Frequency, and Manually Applied Directional Perception tests avg. 94.44^%, 79.17%, and 100%) and responses from the participants indicating that HapticLink may aid during single or double lower-limb amputee ambulation after establishing haptic feedback intensity comfort. Finally, the successful qualitative tests with a double lower-limb amputee imply the haptic feedback may be sufficient without requiring sensor fusion on the part of the participant from both the VMs and the proprioception of the contralateral leg. Clinical Relevance--- This establishes the utility of a simple, stand-alone 4:4 force sensor and haptic motor feedback system to aid during single or double lower-limb amputee ambulation.

Advanced Materials and Technologies for Touch Sensing in Prosthetic Limbs

Neuroscience studies have proved that the absence of proper tactile feedback can affect human behavior. A qualitative and quantitative growth in flexible artificial touch sensing technologies has been witnessed over the recent years. The development of flexible, sensitive, cost-effective, and durable artificial tactile sensors is crucial for prosthetic rehabilitation. Many researchers are working on realizing a smart touch sensing system for prosthetic devices. To mimic the human sensory system is extremely difficult. The practical uses of the newly invented techniques in the industry are limited by complex fabrication processes and lack of proper data processing techniques. Many compatible flexible substrates, materials, and strategies for tactile sensors have been identified to enhance the amputee population. This paper reviews the flexible substrates, functional materials, preparation methods, and several computational techniques for artificial tactile sensors.

Effects of vibrotactile feedback and grasp interface compliance on perception and control of a sensorized myoelectric hand

Current myoelectric prosthetic limbs are limited in their ability to provide direct sensory feedback to users, which increases attentional demands and reliance on visual cues. Vibrotactile sensory substitution (VSS), which can be used to provide sensory feedback in a non-invasive manner has demonstrated some improvement in myoelectric hand control. In this work, we developed and tested two VSS configurations: one with a single burst-rate modulated actuator and another with a spatially distributed array of five coin tactors. We performed a direct comparative assessment of these two VSS configurations with able-bodied subjects to investigate sensory perception, myoelectric control of grasp force and hand aperture with a prosthesis, and the effects of interface compliance. Six subjects completed a sensory perception experiment under a stimulation only paradigm; sixteen subjects completed experiments to compare VSS performance on perception and graded myoelectric control during grasp force and hand aperture tasks; and ten subjects completed experiments to investigate the effect of mechanical compliance of the myoelectric hand on the ability to control grasp force. Results indicated that sensory perception of vibrotactile feedback was not different for the two VSS configurations in the absence of active myoelectric control, but it was better with feedback from the coin tactor array than with the single actuator during myoelectric control of grasp force. Graded myoelectric control of grasp force and hand aperture was better with feedback from the coin tactor array than with the single actuator, and myoelectric control of grasp force was improved with a compliant grasp interface. Further investigations with VSS should focus on the use of coin tactor arrays by subjects with amputation in real-world settings and on improving control of grasp force by increasing the mechanical compliance of the hand.

Latest technology in minimally invasive thoracic surgery

From the introduction of video-assisted thoracoscopic surgery (VATS) in the 1990s, to performing major lung resections using a uniportal VATS approach, technology has paved the way for the development of minimally invasive thoracic surgery. Natural orifice access to achieve a 'no port' approach, is also on the rise, with advancements in bronchoscopic techniques for diagnosis and therapy, as well as development of soft robotics to achieve desired flexibility, dexterity and stability in future platforms, which may involve in vivo deployment to bring the surgeon totally inside the body. Development of haptic feedback in robotic platforms to enhance the surgical experience is also a major goal, with vibrotactile and mechanical feedback generation, to replicate the traditional touch. In addition, the aid of technology in the form of procedural guidance mechanisms, like augmented reality, will further improve the safety and accuracy of future operations.

Portable haptic device for lower limb amputee gait feedback: Assessing static and dynamic perceptibility

Loss of joints and severed sensory pathway cause reduced mobility capabilities in lower limb amputees. Although prosthetic devices attempt to restore normal mobility functions, lack of awareness and control of limb placement increase the risk of falling and causing amputee to have high level of visual dependency. Haptic feedback can serve as a cue for gait events during ambulation thus providing sense of awareness of the limb position. This paper presents a wireless wearable skin stretch haptic device to be fitted around the thigh region. The movement profile of the device was characterized and a preliminary work with able-bodied participants and an above-knee amputee to assess the ability of users to perceive the delivered stimuli during static and dynamic mode is reported. Perceptibility was found to be increasing with stretch magnitude. It was observed that a higher magnitude of stretch was needed for the stimuli to be accurately perceived during walking in comparison to static standing, most likely due to the intense movement of the muscle and increased motor skills demand during walking activity.