Robotic artificial muscles (RAMs) are promising power sources for medical fields such as surgical robotics. However, existing RAMs are challenged by scalability, material costs and fabrications. The nonlinear hysteresis in fluid-driven RAMs causes oscillations in open-loop systems. To circumvent these limitations, this letter introduces hydraulically soft microtubule artificial muscle (SMAM) that is low-cost and scalable, yet simple to fabricate. The SMAM, which only requires a flexible silicone microtube and a hollow micro-coil, is elongated or contracted under a fluid pressure. The SMAM presents an ideal candidate for flexible robotic systems such as endoscopic surgical robots. Experiments are conducted to characterize the SMAMs. Results show that the hysteresis profiles between the input syringe plunger position and output position are stable regardless of its configuration, as opposed to the highly variable responses for the tendon-sheath mechanisms. A new nonlinear model is developed to characterize the asymmetric hysteresis phenomena of the SMAM. Compared to the Bouc-Wen hysteresis models, the developed model presents a better capture of hysteresis. To demonstrate the muscle capability, a SMAMs-driven pulley and a flexible surgical arm are given. The new SMAM and its asymmetric hysteresis model are expected to provide a path for the development of rapidly efficient and low-cost soft actuators for use in flexible medical devices and surgical robotic systems.

Soft actuators (SAs) have been used in many compliant robotic structure and wearable devices, due to their safe interaction with the wearers. Despite advances, the capability of current SAs is limited by scalability, high hysteresis, and slow responses. In this paper, a new class of soft, scalable, and high-aspect ratio fiber-reinforced hydraulic SAs is introduced. The new SA uses a simple fabrication process of insertion where a hollow elastic rubber tube is directly inserted into a constrained hollow coil, eliminating the need for the manual wrapping of an inextensible fiber around a long elastic structure. To provide high adaptation to the user skin for wearable applications, the new SAs are integrated into flexible fabrics to form a wearable fabric sleeve. To monitor the SA elongation, a soft liquid metal-based fabric piezoresistive sensor is also developed. To capture the nonlinear hysteresis of the SA, a novel asymmetric hysteresis model which only requires five model parameters in its structure is developed and experimentally validated. The new SAs-driven wearable robotic sleeve is scalable, highly flexible, and lightweight. It can also produce a large amount of force of around 23 N per muscle at around 30% elongation, to provide useful assistance to the human upper limbs. Experimental results show that the soft fabric sleeve can augment a user’s performance when working against a load, evidenced by a significant reduction on the muscular effort, as monitored by electromyogram (EMG) signals. The performance of the developed SAs, soft fabric sleeve, soft liquid metal fabric sensor, and nonlinear hysteresis model reveal that they can effectively modulate the level of assistance for the wearer. The new technologies obtained from this work can be potentially implemented in emerging assistive applications, such as rehabilitation, defense, and industry.

We developed a foot interface enabling an operator to control a robotic arm with four degrees of freedom in continuous directions and speeds. This interface may enable surgeons to operate one of the multiple tools required during robot-aided surgery. In this paper, we first test whether this interface can be used to carry out complex manipulation as is required in surgery. Second we compare the performance of ten naive operators using this new pedal interface and a traditional button interface providing axis-by-axis constant-speed control. Testing was carried out on geometrically complex path-following tasks similar to laparoscopic training. Movement precision, time and smoothness are analyzed. The results demonstrate that the continuous pedal interface can be used to control a robot for complex motion tasks. The subjects kept the average error rate at a low level of around 2.6% with both interfaces, but the pedal interface resulted in about 30% faster operation speed and 60% smoother movement, which indicates improved efficiency and user experience as compared with the button interface. A questionnaire shows that controlling the robot with the pedal interface was more intuitive, comfortable, and less tiring than with the button interface.

The heart’s intricate myocardial architecture has been called the Gordian knot of anatomy, an impossible tangle of intricate muscle fibers. This complexity dictates equally complex cardiac motions that are difficult to mimic in physical systems. If these motions could be generated by a robotic system, then cardiac device testing, cardiovascular disease studies, and surgical procedure training could reduce their reliance on animal models, saving time, costs, and lives. This work introduces a bioinspired soft robotic left ventricle simulator capable of reproducing the minutiae of cardiac motion while providing physiological pressures. This device uses thin-filament artificial muscles to mimic the multilayered myocardial architecture. To demonstrate the device’s ability to follow the cardiac motions observed in the literature, we used canine myocardial strain data as input signals that were subsequently applied to each artificial myocardial layer. The device’s ability to reproduce physiological volume and pressure under healthy and heart failure conditions, as well as effective simulation of a cardiac support device, were experimentally demonstrated in a left-sided mock circulation loop. This work also has the potential to deliver faithful simulated cardiac motion for preclinical device and surgical procedure testing, with the potential to simulate patient-specific myocardial architecture and motion.

The advent of soft robots has solved many issues posed by their rigid counterparts, including safer interactions with humans and the capability to work in narrow and complex environments. While much work has been devoted to developing soft actuators and bioinspired mechatronic systems, comparatively little has been done to improve the methods of actuation. Hydraulically soft actuators (HSAs) are emerging candidates to control soft robots due to their fast responses, low noise, and low hysteresis compared to compressible pneumatic ones. Despite advances, current hydraulic sources for large HSAs are still bulky and require high power availability to drive the pumping plant. To overcome these challenges, this work presents a new bioinspired soft and high aspect ratio pumping element (Bio-SHARPE) for use in soft robotic and medical applications. This new soft pumping element can amplify its input volume to at least 8.6 times with a peak pressure of at least 40 kPa. The element can be integrated into existing hydraulic pumping systems like a hydraulic gearbox. Naturally, an amplification of fluid volume can only come at the sacrifice of pumping pressure, which was observed as a 19.1:1 reduction from input to output pressure. The new concept enables a large soft robotic body to be actuated by smaller fluid reservoirs and pumping plant, potentially reducing their power and weight, and thus facilitating drive source miniaturization. The high amplification ratio also makes soft robotic systems more applicable for human-centric applications such as rehabilitation aids, bioinspired untethered soft robots, medical devices, and soft artificial organs. Details of the fabrication and experimental characterization of the Bio-SHARPE and its associated components are given. A soft robotic squid and an artificial heart ventricle are introduced and experimentally validated.