Probably the first thing that comes to mind when you hear the word “robot” is a hard, mechanical body that is impervious to harm. Robots aren’t typically required in modern society to protect against hostile attacks, though. Instead, they must carry out more routine duties including handling fragile goods and dealing with people.
Regrettably, conventional robots struggle to complete these ostensibly easy jobs. They are also bulky and frequently noisy. This is where “soft” robots have the upper hand.
Soft robots are safer than traditional robots because they can adapt to their environments better, absorb shocks better, and are made of “elastomers” (materials with high viscosity and elasticity). This has made it possible for a wide range of applications, including manipulation, wearable technology, and medicine and surgery.
However, many of these soft robots rely on fluidic systems, which still use pumps operated by mechanical parts (motors and bearings). As a result, they are still heavy and noisy.
Using chemical reactions to power pumps is one solution to this issue. Such systems are undoubtedly small and quiet, but they don’t work as well as traditional pumps.
Is there a way to beat this trade-off? Turns out, the answer is yes.
A team of researchers from Shibaura Institute of Technology (SIT), Japan, led by Prof. Shingo Maeda, introduced an “electrohydrodynamic” (EHD) pump that uses electrochemical reactions to drive pumps. The EHD pumps have all the advantages of pumps driven by chemical reactions and none of their issues.
Self-sensing technology has attracted much attention recently for compactifying soft robots. Incorporating sensors in soft robots enhances their multifunctionality, but often makes for complex wiring and bloating. Self-sensing actuation technology can help solve this issue and allow for the miniaturization of soft robots.
Professor Shingo Maeda
Now, in a recent study, the team, including Prof. Maeda, Yu Kawajima, Dr. Yuhei Yamada (all from the Department of Engineering Science and Mechanics, SIT), and Associate Professor Hiroki Shigemune (Department of Electrical Engineering, SIT) has gone one step further, designing a “self-sensing” EHD pump that uses an electrochemical dual transducer (ECDT) to sense the fluid flow, which, in turn, activates electrochemical reactions and increases current.
“Self-sensing technology has attracted much attention recently for compactifying soft robots. Incorporating sensors in soft robots enhances their multifunctionality, but often makes for complex wiring and bloating. Self-sensing actuation technology can help solve this issue and allow for the miniaturization of soft robots,” explains Prof. Maeda.
This paper was made available online on 7th January 2022 and was published in Volume 14 Issue 2 of the journal ACS Applied Materials & Interfaces on 19 January 2022.
The team based the ECDT design on the EHD pump they had previously designed. The pump consisted of a symmetrical arrangement of planar electrodes, which allowed an easy control of the flow direction by simply changing the voltage. Due to the equal strength of the electric fields on both sides, the setup also allowed for an obstruction-free flow in both directions.
The researchers employed mathematical modeling to explain the sensing mechanism and evaluated sensing performance in terms of range of observable flow, rate, sensitivity, responsiveness, and relaxation times.
“The ECDT can easily be integrated into a fluidic system without bloating or complexity,” says Yu Kuwajima, doctoral student at the Smart Materials Laboratory (SIT) and the first author of the study. Additionally, the researchers tested its performance by using it to drive a suction cup to detect, grab, and release objects.
“The advantages of the ECDT are that it does not require any special equipment or complex processing for its fabrication. Moreover, it is small, lightweight, and demonstrates a wide range of sensitivity,” says Prof. Maeda.
However, the ECDT is more than just about soft robot miniaturization. In the future, humans and robots will interact in a way that feels natural and fluid rather than merely coexisting. An exciting prospect to entertain, for sure!
