STUDY OF ELECTROOSMOTIC FLUIDIC ACTUATORS FOR SOFT ROBOTS AND WEARABLES

Soft robotics and wearable devices require actuation technologies that combine mechanical compliance, lightweight structures, and safe operation in contact with the human body. Electro-osmotic pumps (EOPs) represent a promising solution for these applications, as they can generate fluid flow and pressure without moving mechanical components. The use of water as the working fluid is attractive for soft robotic and wearable systems due to its non-toxic nature and wide availability. It also enables the use of EOPs in biological and biomedical applications. However, when water is used, electrolysis can occur at the electrodes, leading to gas bubble formation within the system, compromising pump performance and operational stability. This thesis investigates the performance of water-based electro-osmotic pumps, focusing on the influence of the overall pump design and input signal on their hydraulic output, and on the presence of electrolysis. Different pump design, electrodes geometry and voltage levels (50 V and 100 V) were experimentally investigated by characterizing the pressure–flowrate relationship and evaluating the maximum and average achievable pressure and flow rate values, and therefore the pump efficiency. Scanning electron microscopy (SEM) was also employed to examine the electrode surfaces after repeated operating cycles to assess possible changes associated with degradation. The results obtained show that the mesh-electrode configuration achieved the highest overall performance among the tested designs. Compared with the single electrode configuration, the mesh electrode configuration increased the maximum flowrate of the small pump from 263.3 to 297.1 μL/min at 50 V (+ 13%) and from 531.8 to 796.7 μL/min at 100 V (+50%). Although an input voltage of 100 V produces higher peak flow rate and pressure values, operation at 50 V yields higher average performance over the selected measurement intervals. SEM observations after 20 operating cycles at 50 V and 100 V revealed possible electrode degradation, highlighting the need to investigate the effects of electrochemical processes on long-term performance. In addition, the formation of gas bubbles associated with electrolysis represents an important limitation to stable pump operation. Overall, the research highlights the trade-off between peak hydraulic performance and operational stability in water-based EOPs. For the mesh electrodes EOP, the peak flowrate and pressure at 100 V reach, respectively, 1,33×10^(-5) m^3/s and 52,45 Pa decreasing of about 50% after 200 seconds of operation, due to electrolysis formation. The results demonstrated that increasing the pump dimensions and optimizing the electrode geometry can improve its pressure and flowrate performance. In particular, the mesh-electrode configuration achieved promising results despite its smaller active area, suggesting that further improvements could be obtained by scaling up this design. These findings provide useful insights for the optimization of electro-osmotic pumps, towards their integration into soft robotic and wearable applications.