A reconfigurable tactile display based on polymer MEMS technology

This research focuses on the development of polymer microfabrication technologies for the realization of two major components of a pneumatic tactile display: a microactuator array and a complementary microvalve (control) array. The concept, fabrication, and characterization of a kinematically-stabilized polymeric microbubble actuator (¡°endoskeletal microbubble actuator¡±) were presented. A systematic design and modeling procedure was carried out to generate an optimized geometry of the corrugated diaphragm to satisfy membrane deflection, force, and stability requirements set forth by the tactile display goals. A refreshable Braille cell as a tactile display prototype has been developed based on a 2x3 endoskeletal microbubble array and an array of commercial valves. The prototype can provide both a static display (which meets the displacement and force requirement of a Braille display) and vibratory tactile sensations. Along with the above capabilities, the device was designed to meet the criteria of lightness and compactness to permit portable operation. The design is scalable with respect to the number of tactile actuators while still being simple to fabricate. In order to further reduce the size and cost of the tactile display, a microvalve array can be integrated into the tactile display system to control the pneumatic fluid that actuates the microbubble actuator. A piezoelectrically-driven and hydraulically-amplified polymer microvalve has been designed, fabricated, and tested. An incompressible elastomer was used as a solid hydraulic medium to convert the small axial displacement of a piezoelectric actuator into a large valve head stroke while maintaining a large blocking force. The function of the microvalve as an on-off switch for a pneumatic microbubble tactile actuator was demonstrated. To further reduce the cost of the microvalve, a laterally-stacked multilayer PZT actuator has been fabricated using diced PZT multilayer, high aspect ratio SU-8 photolithography, and molding of electrically conductive polymer composite electrodes.Ph.D.Committee Chair: Allen,Mark; Committee Member: Bucknall,David; Committee Member: Book,Wayne; Committee Member: Griffin,Anselm; Committee Member: Yao,Donggan

Progress and prospects in flexible tactile sensors

Flexible tactile sensors have the advantages of large deformation detection, high fault tolerance, and excellent conformability, which enable conformal integration onto the complex surface of human skin for long-term bio-signal monitoring. The breakthrough of flexible tactile sensors rather than conventional tactile sensors greatly expanded application scenarios. Flexible tactile sensors are applied in fields including not only intelligent wearable devices for gaming but also electronic skins, disease diagnosis devices, health monitoring devices, intelligent neck pillows, and intelligent massage devices in the medical field; intelligent bracelets and metaverse gloves in the consumer field; as well as even brain–computer interfaces. Therefore, it is necessary to provide an overview of the current technological level and future development of flexible tactile sensors to ease and expedite their deployment and to make the critical transition from the laboratory to the market. This paper discusses the materials and preparation technologies of flexible tactile sensors, summarizing various applications in human signal monitoring, robotic tactile sensing, and human–machine interaction. Finally, the current challenges on flexible tactile sensors are also briefly discussed, providing some prospects for future directions

Ground Robotic Hand Applications for the Space Program study (GRASP)

This document reports on a NASA-STDP effort to address research interests of the NASA Kennedy Space Center (KSC) through a study entitled, Ground Robotic-Hand Applications for the Space Program (GRASP). The primary objective of the GRASP study was to identify beneficial applications of specialized end-effectors and robotic hand devices for automating any ground operations which are performed at the Kennedy Space Center. Thus, operations for expendable vehicles, the Space Shuttle and its components, and all payloads were included in the study. Typical benefits of automating operations, or augmenting human operators performing physical tasks, include: reduced costs; enhanced safety and reliability; and reduced processing turnaround time

Design and Development of Sensor Integrated Robotic Hand

Most of the automated systems using robots as agents do use few sensors according to the need. However, there are situations where the tasks carried out by the end-effector, or for that matter by the robot hand needs multiple sensors. The hand, to make the best use of these sensors, and behave autonomously, requires a set of appropriate types of sensors which could be integrated in proper manners. The present research work aims at developing a sensor integrated robot hand that can collect information related to the assigned tasks, assimilate there correctly and then do task action as appropriate. The process of development involves selection of sensors of right types and of right specification, locating then at proper places in the hand, checking their functionality individually and calibrating them for the envisaged process. Since the sensors need to be integrated so that they perform in the desired manner collectively, an integration platform is created using NI PXIe-1082. A set of algorithm is developed for achieving the integrated model. The entire process is first modelled and simulated off line for possible modification in order to ensure that all the sensors do contribute towards the autonomy of the hand for desired activity. This work also involves design of a two-fingered gripper. The design is made in such a way that it is capable of carrying out the desired tasks and can accommodate all the sensors within its fold. The developed sensor integrated hand has been put to work and its performance test has been carried out. This hand can be very useful for part assembly work in industries for any shape of part with a limit on the size of the part in mind. The broad aim is to design, model simulate and develop an advanced robotic hand. Sensors for pick up contacts pressure, force, torque, position, surface profile shape using suitable sensing elements in a robot hand are to be introduced. The hand is a complex structure with large number of degrees of freedom and has multiple sensing capabilities apart from the associated sensing assistance from other organs. The present work is envisaged to add multiple sensors to a two-fingered robotic hand having motion capabilities and constraints similar to the human hand. There has been a good amount of research and development in this field during the last two decades a lot remains to be explored and achieved. The objective of the proposed work is to design, simulate and develop a sensor integrated robotic hand. Its potential applications can be proposed for industrial environments and in healthcare field. The industrial applications include electronic assembly tasks, lighter inspection tasks, etc. Application in healthcare could be in the areas of rehabilitation and assistive techniques. The work also aims to establish the requirement of the robotic hand for the target application areas, to identify the suitable kinds and model of sensors that can be integrated on hand control system. Functioning of motors in the robotic hand and integration of appropriate sensors for the desired motion is explained for the control of the various elements of the hand. Additional sensors, capable of collecting external information and information about the object for manipulation is explored. Processes are designed using various software and hardware tools such as mathematical computation MATLAB, OpenCV library and LabVIEW 2013 DAQ system as applicable, validated theoretically and finally implemented to develop an intelligent robotic hand. The multiple smart sensors are installed on a standard six degree-of-freedom industrial robot KAWASAKI RS06L articulated manipulator, with the two-finger pneumatic SHUNK robotic hand or designed prototype and robot control programs are integrated in such a manner that allows easy application of grasping in an industrial pick-and-place operation where the characteristics of the object can vary or are unknown. The effectiveness of the actual recommended structure is usually proven simply by experiments using calibration involving sensors and manipulator. The dissertation concludes with a summary of the contribution and the scope of further work

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

Ultra conformable and multimodal tactile sensors based on organic field-effect transistors

Cognitive psychology is the branch of psychology related to all the processes by which sensory input is transformed, processed and used. Academic and industrial research has always invested time and resources to develop devices capable to simulate the behavior of the organs where the perceptions are located. In recent years, in fact, there have been numerous discoveries related to new materials, and new devices, capable of reproducing, in a reliable manner, the sensory behavior of humans. Particular interest in scientific research has been aimed at understanding and reproducing of man's tactile sensations. It is known that, through the receptors of the skin, it is possible to detect sensations such as pain, changes in pressure and/or temperature. The development of tactile sensor technology had a significant increase in the last years of 1970s, thanks to the important surveys of Stojiljkovic, Harmon and Lumelsky who presented the firsts prototype of sensors for artificial skin applications, and summarized the main characteristics and requirements of tactile sensors. Recently, organic electronics has been deeply investigated as technology for the fabrication of tactile sensors using biocompatible materials, which can be deposited and processed on ultra flexible and ultra conformable substrates. In general, the most attractive property of these materials is mainly related to their high mechanical flexibility, which is mandatory for artificial skin applications. The main object of this PhD research activity was the development and optimization of an innovative technology for the realization of physical sensors able to detect pressure and temperature variations, which can be applied in the field of biomedical engineering and biorobotics. By exploiting the particular characteristics of the employed materials, such as mechanical flexibility, the proposed sensors are very suitable to be integrated with flexible structures (for example plastics) as a pressure and temperature sensor, and therefore, ideal for the realization of an artificial skin like. In Chapter 1, the basics of humans somatosensory system will be introduced: after a brief description of tactile thermoreceptors, mechanoreceptors and nociceptors, a definition of electronic skin and its characteristics will be provided. In Chapter 2, a wide analysis of the state of the art will be reported. Several and different examples of tactile sensor (in inorganic and organic technology) will be presented, underlining advantages and disadvantages for each approach. In Chapter 3, the firsts experimental results, obtained in the first part of my PhD program, will be presented. All the steps of the fabrication process of the devices will be described, as well as the measurement setup used for the electrical characterization of the sensors. In Chapter 4, the sensor structure optimization will be presented. It will be demonstrated how the presented devices are able to sense simultaneously thermal and mechanical stimuli. Moreover, it will be demonstrated that, thanks to an alternative and innovative fabrication process, the sensors can be transferred directly on skin, thus proving the suitability of the proposed sensor architecture for tactile applications

DEVELOPMENT OF A NANOCOMPOSITE SENSOR AND ELECTRONIC SYSTEM FOR MONITORING OF LOCOMOTION OF A SOFT EARTHWORM ROBOT

The ability to detect external stimuli and perceive the surrounding areas represents a key feature of modern soft robotic systems, used for exploration of harsh environments. Although people have developed various types of biomimetic soft robots, no integratedsensor system is available to provide feedback locomotion. Here, a stretchable nanocomposite strain sensor with integrated wireless electronics to provide a feedbackloop locomotion of a soft robotic earthworm is presented. The ultrathin and soft strain sensor based on a carbon nanomaterial and a low-modulus silicone elastomer allows for a seamless integration with the body of the soft robot, accommodating large strains derived from bending, stretching, and physical interactions with obstacles. A scalable, costeffective, screen-printing method manufactures an array of strain sensors that are conductive and stretchable over 100% with a gauge factor over 38. An array of stretchable nanomembrane interconnectors enables a reliable connection between soft strain sensors and wireless electronics, while tolerating the robot’s multi-modal movements. A set of computational and experimental studies of soft materials, stretchable mechanics, and hybrid packaging provides key design factors for a reliable, nanocomposite sensor system. The miniaturized wireless circuit, embedded in the robot joint, offers a real-time monitoring of strain changes on the earthworm skin. Collectively, the soft sensor system shows a great potential to be integrated with other flexible, stretchable electronics for applications in soft robotics, wearable devices, and human-machine interfaces.M.S

A vector light sensor for 3D proximity applications: Designs, materials, and applications

In this thesis, a three-dimensional design of a vector light sensor for angular proximity detection applications is realized. 3D printed mesa pyramid designs, along with commercial photodiodes, were used as a prototype for the experimental verification of single-pixel and two-pixel systems. The operation principles, microfabrication details, and experimental verification of micro-sized mesa and CMOS-compatible inverse vector light pixels in silicon are presented, where p-n junctions are created on pyramid’s facets as photodiodes. The one-pixel system allows for angular estimations, providing spatial proximity of incident light in 2D and 3D. A two-pixel system was further demonstrated to have a wider-angle detection. Multilayered carbon nanotubes, graphene, and vanadium oxide thin films as well as carbon nanoparticles-based composites were studied along with cost effective deposition processes to incorporate these films onto 3D mesa structures. Combining such design and materials optimizations produces sensors with a unique design, simple fabrication process, and readout integrated circuits’ compatibility. Finally, an approach to utilize such sensors in smart energy system applications as solar trackers, for automated power generation optimizations, is explored. However, integration optimizations in complementary-Si PV solar modules were first required. In this multi-step approach, custom composite materials are utilized to significantly enhance the reliability in bifacial silicon PV solar modules. Thermal measurements and process optimizations in the development of imec’s novel interconnection technology in solar applications are discussed. The interconnection technology is used to improve solar modules’ performance and enhance the connectivity between modules’ cells and components. This essential precursor allows for the effective powering and consistent operations of standalone module-associated components, such as the solar tracker and Internet of Things sensing devices, typically used in remote monitoring of modules’ performance or smart energy systems. Such integrations and optimizations in the interconnection technology improve solar modules’ performance and reliability, while further reducing materials and production costs. Such advantages further promote solar (Si) PV as a continuously evolving renewable energy source that is compatible with new waves of smart city technology and systems