Silicone-based highly stretchable multifunctional fiber pumps.

Recent advancements on electrohydrodynamic (EHD) soft pumps demonstrate their applicability to various fluid-driven systems such as soft robots, wearable devices, and stretchable electronics. In particular, fiber type EHD pumps reported more recently is a promising pumping element thanks to their versatile fibrous structure. Yet existing EHD fiber pumps are less stretchable and require sophisticated, complex fabrication equipment, implying opportunity for technology advancement. This paper presents a simplified method to create highly stretchable multifunctional fiber EHD pumps. The method employs highly compliant silicone elastomers for the fiber structure that is formed by simple dipping fabrication process. The fabricated pumps (length of 100 mm, inner diameter 4 mm, and mass 5.3 g) exhibit a high stretchability (up to 40% strain) and flow rate and pressure of 167.4 ± 7.6 mL/min (31.6 mL/min/g) and 4.1 ± 0.6 kPa (0.8 kPa/g), respectively. These performances are comparable or even higher than those of previously reported EHD pumps including fiber types. The output performance of the fabricated pumps remain constant for repeated strain cycles (0-25%, up to 2000 cycles) and bending angle up to 180° (corresponding to curvature of 0-30/m). Moreover, the pumps demonstrate unprecedented functionality as a sensor to distinguish the type of fluid inside the tube and to detect strains by reading the capacitance between the electrodes. The characterization result reveals the sensing ability of the pumps as high repeatability up to 30% strain with negligible hysteresis, which is consistent for 5000 cycles.

Polyvinyl chloride-added dibutyl adipate for high-performance electrohydrodynamic pumps.

Electrohydrodynamic (EHD) pumps are a promising driving source for various fluid-driven systems owing to features such as simple structure and silent operation. The performance of EHD pumps depends on the properties of the working fluid, such as conductivity, viscosity, and permittivity. This implies that the tuning of these parameters in a working fluid can enhance the EHD performance. This study reports a method to modify the properties of a liquid for EHD pumps by mixing an additive. Specifically, dibutyl adipate (DBA) and polyvinyl chloride (PVC) are employed as the working fluid and the additive, respectively. The results show that when the concentration of PVC is 0.2%, the flow rate and pressure at applied voltage of 8 kV take highest value of 7.85 µL/s and 1.63 kPa, respectively. These values correspond to an improvement of 109% and 40% for the flow rate and pressure, respectively, compared to the pure DBA (PVC 0%). When the voltage is 10 kV, the flow rate of 10.95 µL/s and the pressure of 2.07 kPa are observed for DBA with PVC concentration of 0.2%. These values are more than five times higher than those observed for FC40 at the same voltage (2.02 µL/s and 0.32 kPa). The results also suggest that optimal conductivity and viscosity values exist for maximizing the EHD performance of a liquid. This demonstrates the validity of the proposed method for realizing high-performance EHD pumps by using additives in the working fluid.

Peristaltic micropump using polyvinyl chloride gels with micropatterned surface.

This paper presents a pump using polyvinyl chloride (PVC) gel. PVC gels are compliant, have a simple structure, and exhibit large deformation at voltages in the range of 100-1000 V, which make them suitable for micropumps. In this study, a PVC gel sheet with a surface pattern that enhances active deformation in the thickness direction was employed for the fabrication of a pump. To this end, the PVC gel sheet was sandwiched between three sets of anode and cathode electrodes, after which voltages were sequentially applied to these electrodes to generate a peristaltic deformation of the gel sheet, thus pushing the liquid and creating a one-directional flow. Various pumps were fabricated using PVC gel sheets with different surface patterns, and the pumps were characterized. The pumps exhibited an outline dimension of 35 mm × 25 mm with a thickness of 4 mm, corresponding to a total volume of 3.5 × 103 mm3. The results revealed that the pump fabricated using a 174-µm-high pyramid-patterned gel sheet generated a flow rate of 224.1 µL/min at an applied voltage of 800 V and a driving frequency of 3 Hz. This observed value is comparable to or better than those of existing pumps based on smart materials.