Out-of-Plane Soft Lithography for Soft Pneumatic Microactuator Arrays

Abstract

Elastic pneumatic actuators are fuelling new devices and applications in soft robotics. Actuator miniaturisation is critical to enable soft microsystems for applications in microfluidics and micromanipulation. This work proposes a fabrication technique to make out-of-plane bending microactuators entirely by soft lithography. The only bonding step required is to seal the embedded fluidic channels, assuring the structural integrity of the microactuators. The process consists of fabricating two SU8 mold halves using different lithographic layers.Polydimethilsiloxane (PDMS) is poured on the bottom mold, which is subsequently aligned and assembled with the top mould. The process allows for out-of-plane actuators with a diameter of 300 µm and for fabricating arrays of up to 36 actuators that are row-addressable.These active micropillars have an aspect ratio of 1:1.5 and when pressurized at 1 bar, show a bending angle of approximately 30°.

Artificial Cilia–Bridging the Gap with Nature

“…The pneumatic microactuator can bend up to 30° when pressurized at 1 bar. [105] To create more spatial asymmetry, Milana et al [25,63] introduced a second eccentric bending channel in the same cilia, enabling programmable spatial asymmetry on top of programmable metachronal, orientational and temporal asymmetry. To assess the role of the asymmetries, the cilia propulsion was tested in glycerol to experience low Reynolds number flow conditions.…”

“…Using lithographic processes, highly accurate cilia carpets can be made that are compatible with magnetic actuation, [93] electric actuation, [77,79] and fluidic actuation. [119] It should be noted that while some molded cilia use lithographically produced molds, [40,105] here lithography is used to directly shape the cilia, increasing the overall accuracy. Whereas molded cilia are typically cast in an upright position, sharing a common support layer, cilia that are fabricated by means of lithography typically show a planar architecture [79] (see Figure 4A).…”

“…This process is heavily applied in conventional soft robotics, [115] albeit on larger scale. In literature the molds are fabricated through either conventional (micro)machining, [104] lithography, [105,116] 3D printing, [97] or by using materials that feature elongated pores. [27] As cilia are high aspect-ratio structures, their release from the mold is particularly challenging.…”

“…(Deng) Reproduced with permission [ 84 ] copyright 2022, John Wiley & Sons. (Milana) Reproduced with permission [ 105 ] copyright 2023, Mary Ann Liebert. (Li) Reproduced with permission [ 83 ] copyright 2022, Nature Publishing Group.…”

Natural Cilia and Pine Needles Combinedly Inspired Asymmetric Pillar Actuators for All-Space Liquid Transport and Self-Regulated Robotic Locomotion

“…Although scientists have proposed some magnetic-response surfaces to enrich the forms of surface structures, − it is still challenging to design intelligent surfaces with flexible transport in all directions and controllable transport speeds. By contrast, magnetic artificial cilia systems, with the ability of active liquid transport, − stand out from various driving principles (light-driven, , electric-driven, , ultrasound-driven, and fluidic-driven , ) due to their convenient control, rapid response, and cross-scale applicability. Nevertheless, these artificial cilia systems are energy-consuming and have a limited transport space; i.e., only the liquid above the tip of artificial cilia can be transported. , Moreover, the switching of cilia-like beating modes still depends on changing external driving magnetic fields; , i.e., the nonself-regulating beating modes of artificial cilia lead to the inconvenient control of the system and make the multifunctional integration challenging.…”