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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

A shape memory alloy (SMA) spring actuator for an active catheter was fabricated by the heat treatment of wound SMA wire on a mandrel. In order to evaluate the characteristics of the fabricated SMA spring actuator, four types of tests were performed, as follows: isothermal loading and unloading, measurement of shape recovery force, temperature follow-up, and load follow-up tests. In this work, it was first developed that the prediction method of the shape recovery force was based on the neural network theory. The prediction results were better than the results from the conventional constitutive equation of SMA. From the experimental results, it was also proved that the following characteristic for loads was better than that for temperature and the following characteristics could be enhanced according to cooling and control methods.

https://iopscience.iop.org/article/10.1088/0964-1726/9/6/311/pdf

Evaluation of the characteristics of a shape memory alloy spring actuator

A simulation study on the thermal buckling behavior of laminated composite shells with embedded shape memory alloy (SMA) wires

The active buckling control of laminated composite beams with embedded shape memory alloy wires

Shape memory alloy (SMA) actuators have attractive advantages such as high power to volume ratio. However, they also have hard nonlinearities including backlash-like hysteresis and saturation. These nonlinearities result in steady-state errors and limit cycle problems when conventional controllers are used for trajectory control. In this paper, time delay control (TDC) is applied to SMA actuators. The TDC is a well-known robust nonlinear controller and does not require a precise mathematical plant model. The dynamics of an SMA actuator was derived based on Liang's model. This dynamics does not only describe the characteristics of SMA actuators very effectively but also helps tune the TDC gains. A control strategy for the SMA actuator was established and examined from the point of view of the influence of an anti-windup scheme and high gain tuning on the control performance. We also conducted experiments on the position control of the SMA actuator and show the results of the TDC in comparison with other control schemes.

https://iopscience.iop.org/article/10.1088/0964-1726/13/1/027/pdf

Time delay control of a shape memory alloy actuator

A co-cured joint, which uses excess resin extracted from the composite material (or the polymer material) as the adhesive, has several advantages compared with the adhesively bonded joint. It has no need of the surface treatment of the composite adherend and any adhesive for bonding. In addition, its manufacturing process is very simple because the bonding process is achieved during the curing process of the composite adherend. Thermal residual stresses are important in analyzing failure of the co-cured joint because composite materials are different from metal alloys in thermal and mechanical properties. In general, effects of the thermal residual stresses on failure of the adhesive joint are analyzed through experimental and analytical results. Therefore in this paper, two design parameters, namely the surface roughness of the steel adherend and the stacking sequence of the composite adherend, are considered for static and fatigue tensile tests of the co-cured single and double lap joints. Stress distribution at the interface between the two adherends is used to analyze failure of the co-cured lap joints through the finite element method. Based on the stress distribution, two failure criteria, namely the three-dimensional Tsai–Wu failure criterion and the Ye-delamination failure criterion, are considered to predict the tensile load bearing capacity of the co-cured lap joints. Finally, effects of thermal residual stresses on failure of the co-cured single and double lap joints with the steel and composite adherends under static and fatigue tensile load conditions are presented through comparing the experimental and analytical results.

Effects of thermal residual stresses on failure of co-cured lap joints with steel and carbon fiber–epoxy composite adherends under static and fatigue tensile loads

Jung-Ju Lee

Papers

Evaluation of the characteristics of a shape memory alloy spring actuator

A simulation study on the thermal buckling behavior of laminated composite shells with embedded shape memory alloy (SMA) wires

The active buckling control of laminated composite beams with embedded shape memory alloy wires

Time delay control of a shape memory alloy actuator

Effects of thermal residual stresses on failure of co-cured lap joints with steel and carbon fiber–epoxy composite adherends under static and fatigue tensile loads