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Material emissivity engineering can boost energy efficiency in cooling and heating systems by tailoring radiative heat exchange. However, practical energy saving often faces challenges due to environmental temperature inhomogeneity, such as building walls encountering both cold sky and hot ground in the summer. Matching the inhomogeneous temperature requires angle-selective emissivity materials. We present a micro-wedge structure for directional thermal emission control. Our design shows a large broadband contrast in directional emissivity (0.9–0.1), with the angular emission range controlled by the micro-wedge geometry and tunable through magnetic coupling. The angle-selective emitter offers better daytime radiative cooling for outdoor vertical surfaces (2°C below isotropic emitters), potentially saving 10%–40% cooling energy, and efficient indoor radiant heating. Harnessing the directional characteristic of thermal emission opens new opportunities in energy efficiency enhancements across various applications, such as space heating and cooling, waste heat recovery, and solar thermal power generation.

Tactile sensing is paramount for robots operating in human-centered environments to help understand interactions with objects. One challenging issue in tactile sensing is the slip detection problem. Currently, most slip detection methods use passive sensors, which only measure force or vibration, but not directly the contact area, which is one of the most reliable parameters for slip detection. Other methods, which do measure contact area such as optical methods often suffer from complex sensor configurations and lack of flexibility for customization. Active sensing, in contrast, has simple sensor configurations, and can also directly measure the contact area to improve the efficiency for slip detection. In this article, a novel active sensing smart skin was developed for incipient slip detection, which leverages piezoelectric transducers as actuators/sensors. First, a robotic fingertip with embedded actuator and sensor was created in which the actuator generates ultrasonic guided waves received by the sensor during a slip scenario. By analyzing the received signals using an attenuation-based method, the entire contact condition evolution can be monitored within 1 ms. Then, an optical method was used to validate the signal attenuation, which correlated consistently with the contact area. Finally, a unique robotic skin was created which demonstrated robust and sensitive response for incipient slip detection.

Political, economic, and technological forces are changing the landscape of engineering. As the world's economies become more interconnected and more competitive, there is an increasing need for organizations to form […]

AbstractThis article describes a creative design activity to introduce engineering students to mechatronic prototyping. Our goal was to find a creative task to increase student confidence and skills in mechanical design, electrical circuits, microcontrollers, and programming. We present the Paper Robot exercise, a design activity that blends everyday materials such as cardboard, with electronic components. This activity was introduced during the 2010–2011 academic year and has been repeated every year since, in a global, industry-sponsored design course at Stanford University. The Paper Robot exercise resulted from the observation that students were intimidated to create functional prototypes with microcontrollers. The teaching team needed a way to quickly introduce tools for programming electronic components and to encourage creative experimentation early in the course. Results include a 100% task performance rate of students that successfully made a robot meeting the minimum requirements. 76% of students reported an increase in knowledge in programming microcontrollers (Arduino), and 69% increased their knowledge in creating electronic circuits out of raw components. This activity may be modified to introduce younger students to mechatronic platforms in STEM education curriculum.

Annuloplasty ring choice and design are critical to the long-term efficacy of mitral valve (MV) repair. DynaRing is a selectively compliant annuloplasty ring composed of varying stiffness elastomer segments, a shape-set nitinol core, and a cross diameter filament. The ring provides sufficient stiffness to stabilize a diseased annulus while allowing physiological annular dynamics. Moreover, adjusting elastomer properties provides a mechanism for effectively tuning key MV metrics to specific patients. We evaluate the ring embedded in porcine valves with an ex-vivo left heart simulator and perform a 150 million cycle fatigue test via a custom oscillatory system. We present a patient-specific design approach for determining ring parameters using a finite element model optimization and patient MRI data. Ex-vivo experiment results demonstrate that motion of DynaRing closely matches literature values for healthy annuli. Findings from the patient-specific optimization establish DynaRing's ability to adjust the anterior–posterior and intercommissural diameters and saddle height by up to 8.8%, 5.6%, 19.8%, respectively, and match a wide range of patient data.

Shared control represents a middle ground between supervisory control and traditional bilateral control in which the remote system can exert control over some aspects of the task while the human operator maintains access to low-level forces and motions. In the case of dexterous telemanipulation, a natural approach is to share control of the object handling forces while giving the human operator direct access to remote tactile and force information at the slave fingertips. We describe a set of experiments designed to determine whether shared control can improve the ability of an operator to handle objects delicately and to determine what combinations of force, visual, and audio feedback provide the best level of performance and operator sense of presence. The results demonstrate the benefits of shared control and the need to carefully choose the types and methods of direct and indirect feedback.

In the fabrication of directional gecko-inspired adhesives, a new capability made possible by the availability of metal molds is hot compression molding. This molding process allows the use of elastomers with much higher toughness than those cast at ambient temperature and pressure, as has been the common case in fabricating adhesives. In addition, it permits fast cycle times (minutes instead of hours), which is useful for volume manufacturing. We present the results of hot compression molding of elastomers in metal molds created with overhanging and tapered microscopic surface features, which give rise to anisotropic adhesion. We show that the adhesive performance so obtained is equivalent to that obtained earlier with polydimethylsiloxane (PDMS).

Materials are traditionally tested either by imposing controlled displacements and measuring the corresponding forces, or by imposing controlled forces. The first of these approaches is more common because it is straightforward to control the displacements of a stiff apparatus and, if the material suddenly fails, little energy is released. However, when testing gecko-inspired adhesives, an applied force paradigm is closer to how the adhesives are loaded in practice. Moreover, we demonstrate that the controlled displacement paradigm can lead to artefacts in the assumed behaviour unless the imposed loading trajectory precisely matches the deflections that would occur in applications. We present the design of a controlled-force system and protocol for testing directional gecko-inspired adhesives and show that results obtained with it are in some cases substantially different from those with controlled-displacement testing. An advantage of the controlled-force testing approach is that it allows accurate generation of adhesive limit curves without prior knowledge of the expected behaviour of the material or the loading details associated with practical applications.

We describe a process for creating durable metal molds for the fabrication of directional, gecko-inspired dry adhesives. The adhesives require microscopic inclined features with a challenging combination of tapered geometry, high aspect ratio, and smooth surface finish. Wedge-shaped features produced by the new metal mold exhibit the same geometry and surface finish as those cast from single-use wax molds and epoxy molds in previous fabrication methods. They also produce the same levels of adhesion and shear stress. The metal molds, and the adhesives cast from them, show no degradation after repeated molding cycles.

Slip, or accidental loss, of grasped biological tissue can have negative consequences in all types of surgery (open, laparoscopic, robot-assisted). This work focuses on slip in robot-assisted surgery (RAS) with the goal of improving the quality of grasping and tool–tissue interactions. We report on a survey of 112 RAS surgeons, the results of which support the value of detecting and reducing slip in a variety of procedures. We conducted validation tests using a thermal slip sensor in a surgical grasper on tissue in vivo and ex vivo. The results of the survey and validation informed a user study to assess whether tissue slip feedback can improve performance and reduce effort in a phantom tissue manipulation task. With slip feedback, experienced subjects were significantly faster to complete the task, dropped tissue less (3% versus 38%), and experienced decreased mental demands and situational stress. These results provide motivation to further develop the sensor technology and incorporate it in robotic surgical equipment.

We present a hand specialized for climbing unstructured rocky surfaces. Articulated fingers achieve grasps commonly used by human climbers. The gripping surfaces are equipped with dense arrays of spines that engage with asperities on hard rough materials. A load-sharing transmission system divides the shear contact force among spine tiles on each phalanx to prevent premature spine slippage or grasp failure. Taking advantage of the hand’s kinematic and load-sharing properties, the wrench space of achievable forces and moments can be computed rapidly. Bench-top tests show agreement with the model, with average wrench space errors of 10–15%, despite the stochastic nature of spine/surface interaction. The model provides design guidelines and control strategy insights for the SpinyHand and can inform future work.

Small aerial robots are limited to short mission times because aerodynamic and energy conversion efficiency diminish with scale. One way to extend mission times is to perch, as biological flyers do. Beyond perching, small robot flyers benefit from manoeuvring on surfaces for a diverse set of tasks, including exploration, inspection and collection of samples. These opportunities have prompted an interest in bimodal aerial and surface locomotion on both engineered and natural surfaces. To accomplish such novel robot behaviours, recent efforts have included advancing our understanding of the aerodynamics of surface approach and take-off, the contact dynamics of perching and attachment and making surface locomotion more efficient and robust. While current aerial robots show promise, flying animals, including insects, bats and birds, far surpass them in versatility, reliability and robustness. The maximal size of both perching animals and robots is limited by scaling laws for both adhesion and claw-based surface attachment. Biomechanists can use the current variety of specialized robots as inspiration for probing unknown aspects of bimodal animal locomotion. Similarly, the pitch-up landing manoeuvres and surface attachment techniques of animals can offer an evolutionary design guide for developing robots that perch on more diverse and complex surfaces.

Micro-aerial vehicles (MAVs) face limited flight times, which adversely impacts their efficacy for scenarios such as first response and disaster recovery, where it might be useful to deploy persistent radio relays and quadrotors for monitoring or sampling. Thus, it is important to enable micro-aerial vehicles to land and perch on different surfaces to save energy by cutting power to motors. We are motivated to use a downward-facing gripper for perching, as opposed to a side-mounted gripper, since it could also be used to carry payloads. In this paper, we predict and verify the performance of a custom gripper designed for perching on smooth surfaces. We also present control and planning algorithms, enabling an underactuated quadrotor with a downward-facing gripper to perch on inclined surfaces while satisfying constraints on actuation and sensing. Experimental results demonstrate the proposed techniques through successful perching on a glass surface at various inclinations, including vertical.

Bioinspiration is an increasingly popular design paradigm, especially as robots venture out of the laboratory and into the world. Animals are adept at coping with the variability that the world imposes. With advances in scientific tools for understanding biological structures in detail, we are increasingly able to identify design features that account for animals' robust performance. In parallel, advances in fabrication methods and materials are allowing us to engineer artificial structures with similar properties. The resulting robots become useful platforms for testing hypotheses about which principles are most important. Taking gecko-inspired climbing as an example, we show that the process of extracting principles from animals and adapting them to robots provides insights for both robotics and biology.

This paper presents design principles for compliant mechanisms used to support and load spines used in climbing rough vertical surfaces. The design principles ensure that constraints associated with spine/surface interactions are satisfied and that when multiple spines are placed in contact with a surface they share the load without premature failures or spine overloading. The design principles are demonstrated with a compliant mechanism that has been used for robotic and human climbing on surfaces such as brick, stucco and concrete.