Biomechanically, sea turtles could be perceived as birds of the ocean as they glide and flap their forelimbs to produce the necessary forces required for locomotion, making sea turtles an interesting animal to study. However, being an endangered species makes studying the sea turtle's biomechanics a complex problem to solve, both technically and ethically, without causing disturbance. This work develops a novel, non-invasive procedure to develop full three-dimensional kinematics for wild sea turtles by filming the animals in Australia's Great Barrier Reef using underwater drones without disturbing them. We found that the wild animals had very different swimming patterns than previous studies on juveniles in captivity. Our findings show that the flipper goes through a closed-loop trajectory with extended sweeping of the flipper tip towards the centre of the carapace to create a clapping motion. We have named this the “sweep stroke” and in contrast to previously described four-stage models, it creates a five-stage cycle swimming locomotion model. The model presented here could lead to a better comprehension of the sea turtle propulsion methods and their fluid–structure interaction.

Children with physical disabilities often have limited performance in daily activities, hindering their physical development, social development and mental health. Therefore, rehabilitation is essential to mitigate the adverse effects of the different causes of physical disabilities and improve independence and quality of life. In the last decade, robotic rehabilitation has shown the potential to augment traditional physical rehabilitation. However, to date, most robotic rehabilitation devices are designed for adult patients who differ in their needs compared to paediatric patients, limiting the devices’ potential because the paediatric patients’ needs are not adequately considered. With this in mind, the current work reviews the existing literature on robotic rehabilitation for children with physical disabilities, intending to summarise how the rehabilitation robots could fulfil children’s needs and inspire researchers to develop new devices. A literature search was conducted utilising the Web of Science, PubMed and Scopus databases. Based on the inclusion–exclusion criteria, 206 publications were included, and 58 robotic devices used by children with a physical disability were identified. Different design factors and the treated conditions using robotic technology were compared. Through the analyses, it was identified that weight, safety, operability and motivation were crucial factors to the successful design of devices for children. The majority of the current devices were used for lower limb rehabilitation. Neurological disorders, in particular cerebral palsy, were the most common conditions for which devices were designed. By far, the most common actuator was the electric motor. Usually, the devices present more than one training strategy being the assistive strategy the most used. The admittance/impedance method is the most popular to interface the robot with the children. Currently, there is a trend on developing exoskeletons, as they can assist children with daily life activities outside of the rehabilitation setting, propitiating a wider adoption of the technology. With this shift in focus, it appears likely that new technologies to actuate the system (e.g. serial elastic actuators) and to detect the intention (e.g. physiological signals) of children as they go about their daily activities will be required.

Sea turtles are recognised as one of the ocean’s most remarkable migratory species, accomplishing journeys that cover thousands of kilometres. This fact is even more extraordinary when considering sea turtles consume mostly low-energy foods. The biology of sea turtles dominates the literature; however, the swimming strategies they employ to achieve their migratory success from a biomechanical and hydrodynamic viewpoint is relatively unexplored. In past research, the sea turtle’s upstroke has been debated among researchers as to whether it is passive or for thrust production. In this work, we recreate a model based on the green sea turtle (Chelonia mydas) and develop an ad hoc testing rig to uncover the secrets behind the sea turtle’s upstroke. Our findings suggest sea turtles utilise a passive upstroke that can substantially lower the animal’s drag coefficient to levels that cause insignificant losses in swim speed despite not developing any thrust force. This can conceivably save the animal a notable amount of energy as the upstroke is responsible for a large percentage of the overall limb beat cycle. These findings could potentially pave a path towards developing high-efficiency bioinspired underwater drone technologies.

During the past decade, wearable devices such as exoskeletons have gained popularity [1] in different fields, such as the military, [2] industry, [3] and rehabilitation. [4] In the latter, rehabilitation exoskeletons are used to restore or maintain the functionality and mobility of people with physical disabilities. [5] These are receiving greater attention as the number of people with disabilities affecting physical performance will increase in the following decades as the population ages and individuals live longer with noncommunicable conditions (e.g., cerebral palsy, stroke, acquired brain injuries, and muscular dystrophies). [6][7][8] Most current exoskeletons use electric motors and rigid links to realize actuation and often have heavy and bulky designs that are difficult to safely wear outside clinical facilities. [9] Hence, researchers in this area are working to develop soft wearable rehabilitation robots (SWRRs), featuring soft actuators that are agreeable to the users as they have increased compliance, adaptability, comfort, safety, and less weight. [10][11][12] Currently, SWRR relies mainly upon two soft robotic technologies, cable-driven and fluidic actuators. For a cable-driven system, the wire is embedded into clothes or tubes and attached to an anchor point. The other side of the wire is connected to an electric motor to generate the desired movement and force by pulling the cable [13,14] (Figure 1a). Alternatively, in fluidic actuation (Hydraulic/Pneumatic), a pressurized fluid is inserted into a chamber made of highly deformable material to generate a displacement [11,15,16] (Figure 1b). However, these require large and heavy external pumps and valves to compress the fluid. [17] Unfortunately, cable-driven and fluidic actuation need cumbersome components (e.g., electric motors, pumps, and valves) to work, compromising the portability of the systems when used in daily life. [18] Therefore, in recent years, research has been committed to developing new actuator technologies that can overcome the drawbacks of the current actuators used in SWRR. These technologies include artificial muscles based on smart materials (AMSMs). AMSMs are soft actuators composed primarily of material with a low Young's modulus similar to that of soft biological materials (10 ^4-10 ^9 Pa) that can sense and directly convert physical stimulus (e.g., light, electrical, heat) into physical displacement. [19][20][21][22][23] Some examples of smart materials are shape-memory alloy (SMA), [24] dielectric elastomer actuators (DEAs), [25] ionic polymer-metal composites (IPMC), [26] shapememory polymers (SMPs), [27] and twisted and coiled polymer actuators (TCPs). [28] Due to their inherent properties and manufacturing processes, AMSM can be fabricated in various shapes, allowing them to be embedded into flexible and deformable wearable devices. [29][30][31][32] Furthermore, it is possible to fabricate robots with a relatively small weight and volume as they present a power density comparable to the skeletal muscles. [33] Neverthe...

Background: Osteotomes are bone cutting tools commonly reused in orthopedic surgical procedures. Despite undergoing rigorous cleaning, visual inspection, and sterilization procedures between every use, the condition of the cutting blade edge is commonly not qualitatively assessed. Subjective feedback from surgeons suggests a large variation in osteotome cutting-edge sharpness is found during use. This study seeks to investigate the retention of osteotome cutting-edge sharpness by comparing the wear resistance of as-supplied, electroless nickel, and titanium nitride coated osteotomes following a series of bone cutting tests. Methods: Changes in edge sharpness were assessed using visual inspection, depth penetration testing that quantified change in the blade sharpness index, and scanning electron microscopy visual analysis. Visual inspection of each osteotome blade edge was then compared to qualitative blade sharpness index measurement. Results: After use, no cutting-edge damage or change in blade sharpness was detected by visual examination of all three osteotomes; however, the as-supplied osteotome demonstrated 50% loss of blade sharpness index compared to 30% and 15% reduction for the electroless nickel and titanium nitride coated osteotomes, respectively. This finding was supported by scanning electron microscopy evaluation that found greater mechanical damage had occurred along the cutting edge of the as-supplied osteotome compared to the two coated with wear resistant materials. Conclusions: The rapid loss of blade sharpness found in the as-supplied osteotome supports the degradation in cutting performance frequently reported by surgeons. The findings from this study demonstrate blade sharpness index better detects cutting-edge wear compared to visual inspection. Results from this pilot study also suggest the coating of osteotomes in hard-wearing biocompatible materials assists in retaining cutting-edge sharpness over multiple uses. Further study using a larger sample size is required to validate these findings.