Soft actuators, smart sensors: Innovative sensor allows real-time monitoring of complex systems

Fluidic Elastomer Actuators (FEAs) are pressurized tubes or membranes that can be easily rearranged into complex mechanical devices. They have gained significant attention for their lightweight, flexible nature, making them ideal for robotics and biomedical devices. However, the accurate measurement of their dynamic response and rearrangement is challenging because traditional sensors, such as piezoelectric accelerometers and piezoresistive sensors, are not suitable for freeform surfaces like domed roofs or complex shapes. Their rigid metallic casings restrict large deformations and affect the FEA’s performance.

Additionally, the accurate measurement of dynamic responses in FEAs plays an important role in automobile designing. While designing new cars with high efficiency and safety, the measurement of vibration and static pressure on the pressurized tires with an inflatable structure are inevitable. These measurements not only reveal the performance of the car, but also their structural health.

Motivated by this gap in technology, a team of scientists led by Professor Naoki Hosoya from Shibaura Institute of Technology (SIT), Japan, explored Dielectric Elastomer Sensor (DES) to address this challenge. The team consisted of Mr. Haruyuki Kurata from SIT, Japan, Dr. Ardi Wiranata from the University of Gadjah Mada, Professor Shingo Maeda from the Institute of Science Tokyo, Dr. David Garcia Cava from The University of Edinburgh, and Dr. Francesco Giorgio-Serchi from The University of Edinburgh. This study, published online in Measurement, on December 30, 2024, explored how DESs can be used to measure the pressure and vibration response on soft fluidic structures. As Prof. Hosoya notes, “Our study explores how DES can be effectively implemented for real-time state estimation and control of soft fluidic actuators.”

To understand the working of this sensor, the team of scientists fabricated a capacitive-type DES using polydimethylsiloxane (PDMS) and carbon nanotubes. This sensor was tested to measure the vibration response of soft fluidic systems under pneumatic actuation and was capable of measuring vibrations up to 100 Hz. The device measured vibration and static pressure by capturing the change in capacitance. When the DES is subjected to an external force, leading to a deformation, the capacitance increases. The team found that DES exhibited a linear response to vibration amplitude, with its sensitivity increasing as static pressure decreased.

Prof. Hosoya explains, “The mass and rigidity of the conventional sensors like piezoelectric accelerometers and piezoresistive sensors strongly influence the dynamic characteristics of the underlying inflatable structures, likely hindering the nominal operation of the actuator.” Unlike piezoresistive sensors, DES is flexible and can withstand large deformative rearrangements, making them ideal for real-time monitoring of FEAs.

These findings highlight the potential of DES as a valuable sensing device for soft robotics and health monitoring. The ability of DES to function in complex, deformative environments allows it to set a new standard for applications in robotics, biomedical devices, and large-scale infrastructure. Prof. Hosoya mentions, “DES allows capturing fast dynamic response of highly deformable devices or structure, revealing potential role in soft robotics control and structural monitoring.”

Finally, Prof. Hosoya concludes, “These results indicate that lightweight, highly stretchable DESs can be conveniently used as embedded units within complex fluidic networks, aiding in monitoring of this type of actuators, ultimately facilitating their observation and control without posing any constraint to their operation.”   

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Reference

Title of original paper: Dynamic response characterization of soft fluidic actuators via dielectric elastomer sensors

Journal: Measurement

DOI: https://doi.org/10.1016/j.measurement.2024.116616

About Shibaura Institute of Technology (SIT), Japan

Shibaura Institute of Technology (SIT) is a private university with campuses in Tokyo and Saitama. Since the establishment of its predecessor, Tokyo Higher School of Industry and Commerce, in 1927, it has maintained “learning through practice” as its philosophy in the education of engineers. SIT was the only private science and engineering university selected for the Top Global University Project sponsored by the Ministry of Education, Culture, Sports, Science and Technology and had received support from the ministry for 10 years starting from the 2014 academic year. Its motto, “Nurturing engineers who learn from society and contribute to society,” reflects its mission of fostering scientists and engineers who can contribute to the sustainable growth of the world by exposing their over 9,500 students to culturally diverse environments, where they learn to cope, collaborate, and relate with fellow students from around the world.

Website: https://www.shibaura-it.ac.jp/en/

About Professor Naoki Hosoya from Shibaura Institute of Technology, Japan

Dr. Naoki Hosoya is a Professor in the Department of Engineering Science and Mechanics

at Shibaura Institute of Technology. He holds a Ph.D. from Tokyo Metropolitan University and has over 180 publications, 25,000 reads, and more than 1,500 citations. His research focuses on dielectric elastomer actuator, laser techniques for vibration or acoustic testing, structural dynamics, vibrational control, and acoustic analysis. Prof. Hosoya is a member of several professional organizations, including the Japan Society of Applied Physics and Japan Society of Mechanical Engineers. He has held academic positions at SIT since 2007.

Funding Information

This study was funded by Japan Society for the Promotion of Science and their support under the Fostering Joint International Research (B) (Grant No. JP22KK0053) and Grant-in-Aid for Scientific Research (B) (Grant No. JP24K00838).