A Review of Smart Materials in Tactile Actuators for Information Delivery

As the largest organ in the human body, the skin provides the important sensory channel for humans to receive external stimulations based on touch. By the information perceived through touch, people can feel and guess the properties of objects, like weight, temperature, textures, and motion, etc. In fact, those properties are nerve stimuli to our brain received by different kinds of receptors in the skin. Mechanical, electrical, and thermal stimuli can stimulate these receptors and cause different information to be conveyed through the nerves. Technologies for actuators to provide mechanical, electrical or thermal stimuli have been developed. These include static or vibrational actuation, electrostatic stimulation, focused ultrasound, and more. Smart materials, such as piezoelectric materials, carbon nanotubes, and shape memory alloys, play important roles in providing actuation for tactile sensation. This paper aims to review the background biological knowledge of human tactile sensing, to give an understanding of how we sense and interact with the world through the sense of touch, as well as the conventional and state-of-the-art technologies of tactile actuators for tactile feedback delivery

Aerospace medicine and biology: A continuing bibliography with indexes (supplement 352)

This bibliography lists 147 reports, articles and other documents introduced into the NASA Scientific and Technical Information System during July 1991. Subject coverage includes: aerospace medicine and psychology, life support systems and controlled environments, safety equipment, exobiology and extraterrestrial life, and flight crew behavior and performance

Piezoelectric Materials for Medical Applications

This chapter describes the history and development strategy of piezoelectric materials for medical applications. It covers the piezoelectric properties of materials found inside the human body including blood vessels, skin, and bones as well as how the piezoelectricity innate in those materials aids in disease treatment. It also covers piezoelectric materials and their use in medical implants by explaining how piezoelectric materials can be used as sensors and can emulate natural materials. Finally, the possibility of using piezoelectric materials to design medical equipment and how current models can be improved by further research is explored. This review is intended to provide greater understanding of how important piezoelectricity is to the medical industry by describing the challenges and opportunities regarding its future development

Flexible tactile digital feedback for clinical applications

Trauma and damage to the delicate structures of the inner ear frequently occurs during insertion of electrode array into the cochlea. This is strongly related to the excessive manual insertion force of the surgeon without any tool/tissue interaction feedback. The research is examined tool-tissue interaction of large prototype scale (12.5:1) digit embedded with distributive tactile sensor based upon cochlear electrode and large prototype scale (4.5:1) cochlea phantom for simulating the human cochlear which could lead to small scale digit requirements. This flexible digit classified the tactile information from the digit-phantom interaction such as contact status, tip penetration, obstacles, relative shape and location, contact orientation and multiple contacts. The digit, distributive tactile sensors embedded with silicon-substrate is inserted into the cochlea phantom to measure any digit/phantom interaction and position of the digit in order to minimize tissue and trauma damage during the electrode cochlear insertion. The digit is pre-curved in cochlea shape so that the digit better conforms to the shape of the scala tympani to lightly hug the modiolar wall of a scala. The digit have provided information on the characteristics of touch, digit-phantom interaction during the digit insertion. The tests demonstrated that even devices of such a relative simple design with low cost have potential to improve cochlear implants surgery and other lumen mapping applications by providing tactile feedback information by controlling the insertion through sensing and control of the tip of the implant during the insertion. In that approach, the surgeon could minimize the tissue damage and potential damage to the delicate structures within the cochlear caused by current manual electrode insertion of the cochlear implantation. This approach also can be applied diagnosis and path navigation procedures. The digit is a large scale stage and could be miniaturized in future to include more realistic surgical procedures

Soft Tactile Sensors for Mechanical Imaging

Tactile sensing aims to electronically capture physical attributes of an object via mechanical contact. It proves indispensable to many engineering tasks and systems, in areas ranging from manufacturing to medicine and autonomous robotics. Biological skin, which is highly compliant, is able to perform sensing under challenging and highly variable conditions with levels of performance that far exceed what is possible with conventional tactile sensors, which are normally fabricated with non-conforming materials. The development of stretchable, skin-like tactile sensors has, as a result, remained a longstanding goal of engineering. However, to date, artificial tactile sensors that might mimic both the mechanical and multimodal tactile sensory capabilities of biological skin remain far from realization, due to the challenges of fabricating spatially dense, mechanically robust, and compliant sensors in elastic media. Inspired by these demands, this dissertation addresses many aspects of the challenging problem of engineering skin-like electronic sensors. In the first part of the thesis, new methods for the design and fabrication of thin, highly deformable, high resolution tactile sensors are presented. The approach is based on a novel configuration of arrays of microfluidic channels embedded in thin elastomer membranes. To form electrodes, these channels are filled with a metal alloy, eutectic Gallium Indium, that remains liquid at room temperature. Using capacitance sensing techniques, this approach achieves sensing resolutions of 1 mm$^{-1}$. To fabricate these devices, an efficient and robust soft lithography method is introduced, based on a single step cast. An analytical model for the performance of these devices is derived from electrostatic theory and continuum mechanics, and is demonstrated to yield excellent agreement with measured performance. This part of the investigation identified fundamental limitations, in the form of nonmonotonic behavior at low strains, that is demonstrated to generically affect solid cast soft capacitive sensors. The next part of the thesis is an investigation of new methods for designing soft tactile sensors based on multi-layer heterogeneous 3D structures that combine active layers, containing embedded liquid metal electrodes, with passive and mechanically tunable layers, containing air cavities and micropillar geometric supports. In tandem with analytical and computational modeling, these methods are demonstrated to facilitate greater control over mechanical and electronic performance. A new soft lithography fabrication method is also presented, based on the casting, alignment, and fusion of multiple functional layers in a soft polymer substrate. Measurements indicate that the resulting devices achieve excellent performance specifications, and avoid the limiting nonmonotonic behavior identified in the first part of the thesis. In order to demonstrate the practical utility of the devices, we used them to perform dynamic two-dimensional tactile imaging under distributed indentation loads. The results reflect the excellent static and dynamic performance of these devices. The final part of the thesis investigates the utility of the tactile sensing methods pursued here for imaging lumps embedded in simulated tissue. In order to facilitate real-time sensing, an electronic system for fast, array based measurement of small, sub-picofarad (pF) capacitance levels was developed. Using this system, we demonstrated that it is possible to accurately capture strain images depicting small lumps embedded in simulated tissue with either an electronic imaging system or a sensor worn on the finger, supporting the viability of wearable sensors for tactile imaging in medicine. In conclusion, this dissertation confronts many of the most vexing problems arising in the pursuit of skin-like electronic sensors, including fundamental operating principles, structural and functional electronic design, mechanical and electronic modeling, fabrication, and applications to biomedical imaging. The thesis also contributes knowledge needed to enable applications of tactile sensing in medicine, an area that has served as a key source of motivation for this work, and aims to facilitate other applications in areas such as manufacturing, robotics, and consumer electronics.Ph.D., Electrical Engineering -- Drexel University, 201

Engineering derivatives from biological systems for advanced aerospace applications

The present study consisted of a literature survey, a survey of researchers, and a workshop on bionics. These tasks produced an extensive annotated bibliography of bionics research (282 citations), a directory of bionics researchers, and a workshop report on specific bionics research topics applicable to space technology. These deliverables are included as Appendix A, Appendix B, and Section 5.0, respectively. To provide organization to this highly interdisciplinary field and to serve as a guide for interested researchers, we have also prepared a taxonomy or classification of the various subelements of natural engineering systems. Finally, we have synthesized the results of the various components of this study into a discussion of the most promising opportunities for accelerated research, seeking solutions which apply engineering principles from natural systems to advanced aerospace problems. A discussion of opportunities within the areas of materials, structures, sensors, information processing, robotics, autonomous systems, life support systems, and aeronautics is given. Following the conclusions are six discipline summaries that highlight the potential benefits of research in these areas for NASA's space technology programs

Identification of Mechanical Properties of Nonlinear Materials and Development of Tactile Displays for Robotic Assisted Surgery Applications

This PhD work presents novel methods of mechanical property identification for soft nonlinear materials and methods of recreating and modeling the deformation behavior of these nonlinear materials for tactile feedback systems. For the material property identification, inverse modeling method is employed for the identification of hyperelastic and hyper-viscoelastic (HV) materials by use of the spherical indentation test. Identification experiments are performed on soft foam materials and fresh harvested bovine liver tissue. It is shown that reliability and accuracy of the identified material parameters are directly related to size of the indenter and depth of the indentation. Results show that inverse FE modeling based on MultiStart optimization algorithm and the spherical indentation, is a reliable and scalable method of identification for biological tissues based on HV constitutive models. The inverse modeling method based on the spherical indentation is adopted for realtime applications using variation and Kalman filter methods. Both the methods are evaluated on hyperelastic foams and biological tissues on experiments which are analogous to the robot assisted surgery. Results of the experiments are compared and discussed for the proposed methods. It is shown that increasing the indentation rate eliminates time dependency in material behavior, thus increases the successful recognition rate. The deviation of an identified parameter at indentation rates of V=1, 2 and 4 mm/s was found as 28%, 21.3% and 7.3%. It is found that although the Kalman filter method yields less dispersion in identified parameters compared to the variance method, it requires almost 900 times more computation power compared to the variance method, which is a limiting factor for increasing the indentation rate. Three bounding methods are proposed and implemented for the Kalman filter estimation. It was found that the Projection and Penalty bounding methods yield relatively accurate results without failure. However, the Nearest Neighbor method found with a high chance of non-convergence. The second part of the thesis is focused on the development of tactile displays for modeling the mechanical behavior of the nonlinear materials for human tactile perception. An accurate finite element (FE) model of human finger pad is constructed and validated in experiments of finger pad contact with soft and relatively rigid materials. Hyperfoam material parameters of the identified elastomers from the previous section are used for validation of the finger pad model. A magneto-rheological fluid (MRF) based tactile display is proposed and its magnetic FE model is constructed and validated in Gauss meter measurements. FE models of the human finger pad and the proposed tactile display are used in a model based control algorithm for the proposed display. FE models of the identified elastomers are used for calculation of control curves for these elastomers. An experiment is set up for evaluation of the proposed display. Experiments are performed on biological tissue and soft nonlinear foams. Comparison between curves of desired and recreated reaction force from subject's finger pad contact with the display showed above 84% accuracy. As a complementary work, new modeling and controlling approaches are proposed and tested for tactile displays based on linear actuators. Hertzian model of contact between the human finger pad and actuator cap is derived and curves of material deformation are obtained and improved based on this model. A PID controller is designed for controlling the linear actuators. Optimization based controller tuning approach is explained in detail and robust stability of the system is also investigated. Results showed maximum tracking error of 16.6% for the actuator controlled by the PID controller. Human subject tests of recreated softness perception show 100% successful recognition rate for group of materials with high difference in their softness

Advanced Sensing and Image Processing Techniques for Healthcare Applications

This Special Issue aims to attract the latest research and findings in the design, development and experimentation of healthcare-related technologies. This includes, but is not limited to, using novel sensing, imaging, data processing, machine learning, and artificially intelligent devices and algorithms to assist/monitor the elderly, patients, and the disabled population