Liquid Salts Bring Pushbutton Lenses Into Focus
First-ever piezoelectric liquids could spark new technologies in optics and hydraulics:
Scientists have discovered the first known piezoelectric liquids, which are able to convert mechanical force to electric charge, and vice versa. The generally environmentally friendly nature of these materials suggests they may find many applications beyond standard piezoelectric compounds, such as novel, electrically controlled optics and hydraulics. However, much remains unknown about how they work, and therefore what they may be capable of.
Piezoelectricity was first discovered in 1880. The effect has since found a wide range of applications, including cellphone speakers, inkjet printers, ultrasound imaging, sonar equipment, pressure sensors, acoustic guitar pickups, and diesel fuel injectors.
Until now, all known piezoelectric materials were solid. Now scientists have for the first time discovered piezoelectric liquids. They detailed their findings in a study online 9 March in the Journal of Physical Chemistry Letters.
The researchers experimented with ionic liquids. These fluids are salts—compounds that are each made of both a positively charged cation and a negatively charged anion—that are liquid at unusually low temperatures. In comparison, table salt melts at roughly 800 ºC.
"They are often relatively viscous—think about them like motor oil, or maple syrup," says Gary Blanchard, one of the authors of the study and a professor of chemistry at Michigan State University, in East Lansing.
Blanchard says the team was conducting standard experiments designed to better understand the basic properties of liquid-state salts (also known as ionic liquids). The team found that two different room-temperature ionic liquids each generated electricity when a piston squeezed them within a cylinder. The strength of the effect the researchers observed was directly proportional to the force applied.
"It shocked the hell out of us to see that," Blanchard says. "Nobody had ever seen the piezoelectric effect in liquids before."
Blanchard and his colleagues found that the optical properties of these ionic liquids could alter dramatically in response to electric current. For instance, when the researchers placed these fluids in a lens-shaped container, they found that an electric charge could modify how much the liquids bent light, "changing the focal length of the lens," Blanchard says.
Journal Reference:
Ionic Liquids Exhibit the Piezoelectric Effect, Md. Iqbal Hossain and G. J. Blanchard, The Journal of Physical Chemistry Letters 2023 14 (11), 2731-2735
DOI: 10.1021/acs.jpclett.3c00329
(Score: 2) by VLM on Thursday March 30 2023, @02:50PM (1 child)
That's pretty cool, I remember playing with magnetorheological fluids in the 90s and they were incredibly abrasive whereas some of these might be industrially useful.
Your typical magnetic fluid at the time was ground up steel in oil.
(Score: 1, Interesting) by Anonymous Coward on Thursday March 30 2023, @03:41PM
Someone that works with magnetic fluid in automotive dampers commented that the iron in the fluid now is molecular, he compared it to the iron in hemoglobin (but a different molecule). Quite a few cars use these dampers, see list at the end of https://en.wikipedia.org/wiki/MagneRide [wikipedia.org]