Staff member

Soft and flexible robotics is an emerging field that attracts a huge interest due to its ability to produce bioinspired devices that are easily adaptable to the environment. Biohybrid Machines (BHM) represent a category of soft robots that integrate biological tissues, such as engineered muscle tissues, as actuating systems. Although these devices present several advantages in some applications, their proper actuation still represents a challenge for researchers. This paper focuses on the development of a portable and programmable electrical stimulator designed to control muscle fiber-based biohybrid actuators. The stimulator, made using off-the-shelf components, was designed as a stacking of three independent printed circuit boards (PCBs), connected vertically in order to result in a final device with compact dimensions of 59 mm 28 mm 25 mm. The stimulation circuit is capable of delivering currents up to 18 mA with a voltage compliance of ± 90 V, and a power consumption of approximately 1.3 W. The device’s ability to induce twitch and tetanic contractions in a biohybrid actuator is demonstrated in different stimulation conditions. A practical application was also explored through a test case involving a flexible catheter prototype controlled by a biohybrid actuator, demonstrating its potential utility in a BHMs.

JTD

Gradients are widespread in nature, including within the human body, making the study of nanomotors’ collective dynamics in gradients crucial to advancing biomedical applications and deepening the understanding of natural active matters. However, the comprehensive understanding of nanomotors’ collective dynamics under gradients remains underexplored, particularly. This study employs urease-based nanomotors (UrNMs) as a model system to explore their collective dynamics within a urea gradient, revealing three fundamental principles that govern their behavior: density-driven convection, UrNMs’ response to the urea gradient, and a coupling effect between UrNMs and their environment. Initially, migration is dominated by convection-induced motion arising from the steep gradient. As convection gradually diminishes, UrNMs' positive response to the urea gradient becomes the dominant factor governing their migration. Notably, the coupling effect between nanomotors and the gel, plays a crucial role in the migration process. This coupling effect arises from hydrogen bonding between product anions and the gel, which generates ionic gradients. The dominant influence of electric force is validated by pH-controlled experiments. These insights advance the fundamental understanding of gradient-responsive nanomotor behavior and offer inspiration for the design of intelligent, environment-sensitive active systems.

JTD

Skeletal muscle tissue represents an attractive powering component for biohybrid robots, as traditional actuators used in the soft robotic context often rely on complex mechanisms and lack scalability at small dimensions. This article proposes a monolithic biohybrid flexure mechanism actuated by a bioengineered skeletal muscle tissue. The design leverages the contractile properties of a bioengineered skeletal muscle to produce a bending motion in a monolithic, tubular mechanism made of a soft and biocompatible silicone blend. This structure integrates two cylindrical pillars that facilitate force transmission from the bioengineered muscle tissue. Performance assessments reveal excellent contractile and stable behavior upon electrical stimulation, compared to current biohybrid actuation systems, with enhanced performance as the mechanism's internal and external diameters decrease. Finite-element simulations further reveal distinct force-displacement responses in mechanisms with different flexural rigidity. This innovative, scalable, and easy-to-fabricate design represents a significant step forward in the development of novel biohybrid machines.

JTD

Enzymatic nanomotors harvest kinetic energy through the catalysis of chemical fuels. When a drop containing nanomotors is placed in a fuel-rich environment, they assemble into ordered groups and exhibit intriguing collective behaviour akin to the bioconvection of aerobic microorganismal suspensions. This collective behaviour presents numerous advantages compared to individual nanomotors, including expanded coverage and prolonged propulsion duration. However, the physical mechanisms underlying the collective motion have yet to be fully elucidated. Our study investigates the formation of enzymatic swarms using experimental analysis and computational modelling. We show that the directional movement of enzymatic nanomotor swarms is due to their solutal buoyancy. We investigate various factors that impact the movement of nanomotor swarms, such as particle concentration, fuel concentration, fuel viscosity, and vertical confinement. We examine the effects of these factors on swarm self-organization to gain a deeper understanding. In addition, the urease catalysis reaction produces ammonia and carbon dioxide, accelerating the directional movement of active swarms in urea compared with passive ones in the same conditions. The numerical analysis agrees with the experimental findings. Our findings are crucial for the potential biomedical applications of enzymatic nanomotor swarms, ranging from enhanced diffusion in bio-fluids and targeted delivery to cancer therapy. Enzymatic nanomotors exhibit collective behaviour in fuel-rich environments, forming swarms with enhanced propulsion and coverage. This study investigates the factors affecting swarm movement, revealing that solutal buoyancy drives their motion, with potential biomedical applications like targeted drug delivery.

JTD Keywords: Ammonia, Behavior, Carbon dioxide, Catalysis, Computer simulation, Kinetics, Motion, Nanostructures, Powered nanomotors, Propulsion, Urease, Viscosity

The integration of flexible organic electronics in soft robotic devices is a valuable way to enhance their functionality, towards augmented controllability and performance. Nonetheless, this field is generally unexplored. Here, we report a preliminary study on the integration of soft robotic components with Organic Field-Effect Transistor-based strain sensors. Such sensors will be tested as deformation transducer for bioengineered muscle tissues operating as biohybrid actuators. Moreover, the integration of ultra-flexible devices on catheter-like soft robotic supports is discussed.

JTD Keywords: Biohybrid actuators, Biohybrid machine, Catheters, Ofets, Strain sensors