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American Society for Testing and Materials

Human skin is a remarkable organ. It consists of an integrated, stretchable network of sensors that relay information about tactile and thermal stimuli to the brain, allowing us to maneuver within our environment safely and effectively. Interest in large-area networks of electronic devices inspired by human skin is motivated by the promise of creating autonomous intelligent robots and biomimetic prosthetics, among other applications. The development of electronic networks comprised of flexible, stretchable, and robust devices that are compatible with large-area implementation and integrated with multiple functionalities is a testament to the progress in developing an electronic skin (e-skin) akin to human skin. E-skins are already capable of providing augmented performance over their organic counterpart, both in superior spatial resolution and thermal sensitivity. They could be further improved through the incorporation of additional functionalities (e.g., chemical and biological sensing) and desired properties (e.g., biodegradability and self-powering). Continued rapid progress in this area is promising for the development of a fully integrated e-skin in the near future.

25th Anniversary Article: The Evolution of Electronic Skin (E-Skin): A Brief History, Design Considerations, and Recent Progress

Starting from human ?sense of touch,? this paper reviews the state of tactile sensing in robotics. The physiology, coding, and transferring tactile data and perceptual importance of the ?sense of touch? in humans are discussed. Following this, a number of design hints derived for robotic tactile sensing are presented. Various technologies and transduction methods used to improve the touch sense capability of robots are presented. Tactile sensing, focused to fingertips and hands until past decade or so, has now been extended to whole body, even though many issues remain open. Trend and methods to develop tactile sensing arrays for various body sites are presented. Finally, various system issues that keep tactile sensing away from widespread utility are discussed.

Tactile Sensing—From Humans to Humanoids

Advances in soft robotics, materials science, and stretchable electronics have enabled rapid progress in soft grippers. Here, a critical overview of soft robotic grippers is presented, covering different material sets, physical principles, and device architectures. Soft gripping can be categorized into three technologies, enabling grasping by: a) actuation, b) controlled stiffness, and c) controlled adhesion. A comprehensive review of each type is presented. Compared to rigid grippers, end-effectors fabricated from flexible and soft components can often grasp or manipulate a larger variety of objects. Such grippers are an example of morphological computation, where control complexity is greatly reduced by material softness and mechanical compliance. Advanced materials and soft components, in particular silicone elastomers, shape memory materials, and active polymers and gels, are increasingly investigated for the design of lighter, simpler, and more universal grippers, using the inherent functionality of the materials. Embedding stretchable distributed sensors in or on soft grippers greatly enhances the ways in which the grippers interact with objects. Challenges for soft grippers include miniaturization, robustness, speed, integration of sensing, and control. Improved materials, processing methods, and sensing play an important role in future research.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/adma.201707035

Soft Robotic Grippers.

This paper provides a broad overview of medical robot systems used in surgery. After introducing basic concepts of computer-integrated surgery, surgical CAD/CAM, and surgical assistants, it discusses some of the major design issues particular to medical robots. It then illustrates these issues and the broader themes introduced earlier with examples of current surgical CAD/CAM and surgical assistant systems. Finally, it provides a brief synopsis of current research challenges and closes with a few thoughts on the research/industry/clinician teamwork that is essential for progress in the field.

/pdf/medical-robotics-in-computer-integrated-surgery-551rsaf1dd.pdf

Medical robotics in computer-integrated surgery

The influence of a biasing electric field on the propagation of the lowest-order antisymmetrical a0 Lamb wave modes in a bi-layered piezoelectric plate is investigated in this paper. It is found that the velocity shifts for the a0 mode due to presence of the bias field on the 10- µm LiNbO3 film structure are comparable with those observed in surface acoustic waves and Lamb waves in LiNbO3 plates. The fractional change in phase velocity of the layered piezoelectric structure is a linear function of the biasing electric field and can be used in voltage sensors.

Nonlinear Acoustoelastic Interactions of Lamb Waves with LiNbO3 Films Deposited on Sapphire Substrates

In this paper, we present a newly designed flexible optical fiber force sensors which use fiber Bragg gratings and diaphragm and bridge type transducer, to detect a distributed normal force and which is the first step toward realizing a tactile sensor using optical fiber sensors (FBG). The transducer is designed such that it is not affected by chirping and light loss to enhance the performance of the sensors. We also present the design and fabrication process and experimental verification of the prototype sensors.

Flexible Force Sensors Using Fiber Bragg Grating

In this paper the tactile sensor system based on the bending loss of optical fiber sensor is presented. The sensor array was designed with fabric structure. The optical measuring system was composed of LED for light source and CCD camera for the signal light detector. Performance of this tactile sensor system was evaluated in various environments and compared with Harmon`s design criteria. The result shows that load range is 3 g100 g, resolution is 1.5 g, hysteresis error is 1.5%. The response linearity is good and flexibility of sensor array is excellent.

/pdf/development-of-fabric-based-optical-fiber-tactile-sensor-4ds99wzlom.pdf

Development of fabric-based optical fiber tactile sensor using optical fiber bending loss

Distributed optical fiber sensors are effective in the monitoring of large structures because of their large sensing range. In this research, the methods of strain and deflection measurement for bending beams using Brillouin distributed optical fiber sensors were presented. The deflection monitoring of beams makes possible the damage detection of large structures such as bridges. The measured strain with Brillouin distributed optical fiber sensors is expressed as the averaged value within its spatial resolution. Due to the characteristic of the spatial resolution, strain near the ends of a measurement range cannot be correctly measured with respect to the measuring position. Therefore, its compensation is required. The strain measurement method suitable to the sensor characteristic was proposed, and it was verified by the analysis of aluminum-tube beams. The beam deflection could be monitored using the distributed measurement more simply and effectively than using general point-measurement.

Monitoring of beam deflection subjected to bending load using Brillouin distributed optical fiber sensors

In this paper, a new Structural Health Monitoring (SHM) technique for composite laminates through the use of embedded FBG sensors is presented. This method monitors the ply stress states of a laminate and compares them with failure criteria continuously during structures’ service time. The ply stress state of each ply composing the composite laminate can be obtained by embedding three FBG sensors in the laminate based on the classical lamination theory. In this study FBG sensor embedded graphite/epoxy composite laminate specimens were fabricated. With ply stress states being monitored, tension and fatigue tests were performed until laminates’ failure. Experimental results show that laminates experience fracture when the ply stress states are beyond the boundaries of failure criteria. Embedded FBG sensors had good fracture strain and reliability. Therefore, critical damage can be detected by the ply stress states which are close to the boundaries of failure criteria.

Jung-Ju Lee

Papers

Nonlinear Acoustoelastic Interactions of Lamb Waves with LiNbO3 Films Deposited on Sapphire Substrates

Flexible Force Sensors Using Fiber Bragg Grating

Development of fabric-based optical fiber tactile sensor using optical fiber bending loss

Monitoring of beam deflection subjected to bending load using Brillouin distributed optical fiber sensors

Structural Health Monitoring of Composite Laminates by Using Embedded FBG Optical Fiber Sensors