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Nature · 2019

Stretchable pumps for soft machines

V. Cacucciolo, J. Shintake, Y. Kuwajima, S. Maeda, D. Floreano, H. Shea
Nature 572, 516–519 (2019) — EPFL · Shibaura Institute of Technology
First
fully soft pump in the world
0
moving parts
100%
stretchable and bendable
1 g
order of magnitude of the weight

The problem

For over a decade, soft robotics has been developing artificial muscles driven by pressurised fluids. But the fluid has to be pumped, and conventional pumps are rigid, heavy and noisy, anchored outside the robot with tubes and compressors. A soft-bodied machine remained tethered to hard infrastructure — the bottleneck of the entire field.

The innovation

This research demonstrated the first fully soft, stretchable pump: an elastomer channel with flexible electrodes that moves fluid through electrohydrodynamics (EHD). An electric field injects charge into the dielectric liquid and the migrating ions drag the fluid along with them. No gears, no membrane, no rotor: pressure arises directly from electricity, in silence.

working principle of the stretchable pump
Fig. 1 — Working principle: electrodes along the channel inject charge into the liquid, and the ions drag it along, creating a net flow. Cacucciolo, Shintake, Kuwajima, Maeda, Floreano, Shea. Nature 2019
stretchable pump bent between the fingers
Fig. 2 — The pump keeps its performance even when bent, twisted or stretched: it can be integrated into the robot's own body. Cacucciolo, Shintake, Kuwajima, Maeda, Floreano, Shea. Nature 2019
stretchable pump rolled into a ring
Fig. 3 — Fully soft: electrodes and channel bend with the elastomer, here rolled into a ring. Cacucciolo, Shintake, Kuwajima, Maeda, Floreano, Shea. Nature 2019

Why it matters

With a soft, lightweight and silent pump, the fluidic circuit can finally live inside the robot or inside a wearable garment. It is the result that opened the lab's research line on portable fluidic muscles — and the conceptual foundation from which, four years later, the fiber pumps would emerge.

stretchable pump held up to the light
Fig. 4 — Thin, transparent and flexible: a pump small enough to sit inside the machine it drives. Cacucciolo, Shintake, Kuwajima, Maeda, Floreano, Shea. Nature 2019
glove with a stretchable pump on the back of the hand
Fig. 5 — A wearable application: the pump on the back of the hand, inside the glove's fluidic circuit. Cacucciolo, Shintake, Kuwajima, Maeda, Floreano, Shea. Nature 2019