(A) soft high-radix fluidic demultiplexer for controlling multi-chamber soft robot

Abstract

Soft robotics has made significant progress in the last decade, with applications in robotic grippers, rehabilitation devices, and field exploration. Soft robots are different from conventional robots in that they are made of stretchable and flexible materials, allowing for safe interactivity and structural adaptability. While fluidic actuation is a popular method for soft robots, there are still challenges to overcome, such as enhancing functionality and creating a more comprehensive control system that includes the soft controller or pump with the endpoint actuator. Conventional rigid valves and electronics control most soft robots, making them less soft and increasing power consumption. Additionally, independent analogous control of each actuator complicates the structure and control process. In the field of soft robotics, microfluidics has gained attention as a potential method for creating electronic-free, lightweight, and all-soft robots. This approach can also lead to more efficient and compact soft robots through digitization and miniaturization. Soft robots have a high degree of structural flexibility, but the transmission of force or torque depends heavily on the design. This means that if a soft robot bulges unintentionally, efficiency can be lost. To combat this issue, using an array of chambers that can be digitally controlled can improve functionality and reduce unintended expansion. Fluidic circuits are a suitable method for controlling these chambers digitally because they allow a small number of inputs to control many outputs, avoiding the need for excessive fluid or electronic peripherals that might restrict the movement of a relatively low-rigidity soft robot body. Although microfluidics is a promising technology for soft robots, there are limitations when applying the existing system due to differences in scale and physical properties. While microfluidic circuitry utilizes materials such as PDMS for soft robots, only the control membrane is made of soft materials, and most other structures remain rigid. This could hinder the movement of the soft robot if the control systems are not also soft. Furthermore, the current microfluidic circuit fabrication method needs to be modified to produce macro-sized circuits with adequate flow rates for soft robots. This research proposes a soft high-radix demultiplexer for macroscopic soft robots by designing and fabricating a stretchable and flexible fluidic circuit using a serpentine channel-based network. The serpentine structure maintains fluidic control ability through high-stiffness walls, while the soft structure allows controllers to be distributed throughout the robot body. The suggested fabrication process includes laser cutting and layer additive manufacturing, which offer increased design freedom and system scalability. This method ensures sufficient flow rate for driving the robot, and the structure maintains performance despite external stimuli. The demultiplexer, designed for controlling many outputs with few inputs, employs ternary and quaternary inputs with different pressure thresholds, enabling a significant increase in the number of outputs.