Although simple in theory, bubbles and conductive liquids are sealed in a chamber surrounded by electrodes, but in reality the electron level is more complex.
If the liquid is an electrolyte, it should be driven by AC (without DC) to avoid chemical decomposition and corrosion. If the liquid is a metal like mercury or Galinstan, it works with a DC drive, but it’s in a squash ball that doesn’t flow well to the electrodes.
What is needed is a collection of materials and shapes with the right combination of conductivity wettability and viscosity, and the liquid will slosh in the right way.
After trying several, including galinstan, the liquid of choice was water, which was made conductive by a dilute suspension of carbon nanotubes.
It is in a flat-bottomed chamber, with a large number of regularly spaced copper electrodes (12 in the demonstrator) around the edges, and the rest of the floor is covered with a water-repellent fluoropolymer (“Cytop”). I am.
Inside, the top of the chamber is a shallow dome, on which a ring-shaped silver electrode is placed and connected to a voltage source.
The combination of dome angle, liquid properties, and floor repelling allows water to sit on the crescent moon around the wall if the sensor is not flat, and the crescent moon stretches to reach more electrodes when it is nearly flat and large. Tilt it to shorten it. .. The silver ring is arranged so that water is always available.
As a final result, using on-off conductivity without analog measurements allows you to estimate both the tilt direction and the tilt angle by detecting the electrodes shorted to the silver ring by the liquid and their number.
“By using a highly fluid conductive liquid, the sensor can measure not only the tilt direction but also the angle. In the tilted state, the air pocket moves to switch the conductivity and insulation of the electrode. This function “The tilt direction can be detected without an external calculation mechanism,” said Hiroki Ota, a research engineer at YNU. “This function can be extended to measure other physical quantities such as pressure and strain deformation at the same time. We aim to create multi-physical sensors. “
This work has been published by Advanced Materials Technologies as a “liquid-based digital readable tilt sensor”. Supplementary material can be downloaded for free, revealing the shape, materials, and manufacturing process, but only the abstract of the treatise is available for free.
Yokohama National University
Details of this news release
Simplified sensor measures tilt angle and direction with liquid
Yokohama National University
Advanced material technology
10.1002 / admt.202100490
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