University of Maryland:
A soft robotic hand with integrated fluidic circuitry that can play Nintendo
The Bioinspired Advanced Manufacturing (BAM) Laboratory, directed by Prof. Ryan D. Sochol, is a group of researchers at the A. James Clarck school of engineering, University of Maryland, College Park, USA. The BAM Lab focuses on pioneering alternative micro/nanofabrication strategies based on state-of-the-art additive manufacturing technologies, or “3D printing”, to advance biomedical fields. More specifically, they focus on cases requiring device architectures and/or functionalities that would be difficult or infeasible to achieve using conventional manufacturing methods. Recent research topics include 3D Microfluidic Technologies via Direct Laser Writing, Multi-Material Direct Laser Writing, and 3D-printed soft robotics with fluidic circuitry. In the latter topic, the group recently designed and actuated a soft robotic turtle and soft robotic hand by means of pressure. This work was published in Science Advances.
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“Typically, each appendage of a soft robot would typically need its own control line, which can limit portability and usefulness, but by 3D printing soft robots with integrated microfluidic circuits and networks, they can be controlled based on just one pressure input. Enhancing soft robot autonomy in this manner is critical for our emerging applications like soft robotic surgical tools.”
“Controlling soft robots based on a single pressure input is founded on the ability to precisely regulate the pressure magnitude at set times – a capability that we found the MFCS and accompanying Maesflo software was uniquely suited for accomplishing.”
Prof. Ryan D. Sochol
Over the past decade, the field of soft robotics has established itself as distinctively suited for applications that would be difficult or impossible to realize using traditional, rigid robots1,2. “Soft robotics” centers on creating new types of flexible, inflatable robots that are powered using water or air rather than electricity. Using compliant materials actuated by fluidic means brings several benefits, particularly in terms of safety for human-robot interactions, lower costs, and adaptability in geometry for manipulating complex and/or delicate objects1 (for instance, soft robotic sleeves for pumping ailing hearts). However, the emergence of soft robots has presented new challenges associated with controlling the underlying fluidics of such systems. Fabrication of fully-embedded soft robots (i.e. including soft actuators; body features; and fluidic circuit elements) can be challenging depending on the manufacturing method. In addition to manufacturing challenges, stable and fast fluidic control is often a prerequisite for the great functioning of soft robots.
Ryan Sochol’s group addressed manufacturing challenges by developing a novel strategy for additively manufacturing unified soft robotic systems with fully integrated fluidic circuitry in a single print run via multimaterial “PolyJet three-dimensional (3D) printing”. It is an inkjet-based process by which multiple photoreactive materials are dispensed in parallel to produce multi-material 3D objects in a line-by-line, layer-by-layer manner1. To ensure stable flow and fast-response actuation, the group used Fluigent pressure-based flow controllers and dedicated software.
In a research paper published in 2021, the group designed several soft robots and investigated their operation performances. Here, we summarize partial results obtained with the soft robotic hand.
Fluigent systems to finely actuate a soft robotic hand
Soft robotic turtles and a soft robotic hand were first produced by PolyJet 3D printing, and finite element analysis simulations were performed to predict the input pressures required for robot actuation. In addition, circuits elements characterization was performed using Fluigent Flow Units. More information about the design of the soft robots as well as their characterization can be found in the paper1.
To experiment the operation of the soft robotic hand with integrated fluidic circuitry, the group programmed the hand in order to play the Nintendo Entertainment System (NES) Super Mario Bros. video game in real time using a controller. Figure 1 illustrates the setup used for fluidic actuation. All experiments were performed using Fluigent pressure controllers along with the corresponding software. Pressure controllers are connected to two reservoirs, which are connected to inputs of the fluidic hand. Note that in the paper Fluigent MFCS were used, but we now provide the Flow EZ, more compact, and permitting local control if needed.
Figure 1: Illustrating schematic the setup for fluidic hand actuation
An input is kept at constant pressure (PSource = Ps) while the second input is dynamically regulated for actuating the hand (PGate = Pg) (figure 2). Pneumatic experiments are performed by running a custom script via the Fluigent MAESFLO software and Fluigent script module to dynamically regulate the Pg input while maintaining a constant Ps. The soft robotic hand is fixed in place using a clamp, while the base of each fingertip is affixed to the corresponding NES controller button.
Figure 2: Illustrations and analogous circuit diagrams of the four primary states based on distinct PG magnitudes, while a PS input remains constant1.
In this work, a constant Ps input of 18.5 kPa is used, allowing for four Pg states: (i) Pg,Off ≤ 5 kPa, none of the buttons are pressed—Mario is immobile (Fig. 3 i); (ii) Pg,Low ≥ 20 kPa, the right button of the D-pad is pressed—Mario walks (Fig. 3 i); (iii) Pg,Medium ≥ 40 kPa, the B button is also pressed—Mario runs (Fig. 3 iii); and (iv) Pg,High ≥ 60 kPa, all of the buttons are pressed—Mario jumps (Fig. 3 iv)1. It is possible to observe fast response time and high pressure stability for all states.
By taking into considerations time required when executing inflations or deflations in designing the program, the authors managed to complete the first level of Super Mario Bros. in real time, as shown in the short movie below!
Figure 3: Experimental results for completing the first level of the Super Mario Bros. video game in real time in response to a preprogrammed pressure inputs1. Photo credit: Joshua D. Hubbard, Ruben Acevedo and Kristen M. Edwards, University of Maryland, College Park.
In this case study, we demonstrated the use of Fluigent pressure-based flow controllers along with Fluigent Flow Units and dedicated software for precise and fast actuation of a soft robotic hand.
- Hubbard, J. D. et al. Fully 3D-printed soft robots with integrated fluidic circuitry. Sci. Adv. 7, (2021).
- Sochol, R. D. et al. 3D printed microfluidic circuitry via multijet-based additive manufacturing. Lab Chip 16, 668–678 (2016).