J. DAVID CARLSON, PHYSICIST
When it comes to the shakes and shocks caused by potholes, washer-dryers, or when using prosthetic joints, even earthquakes, applied science has got a good vibe. â€œSmart fluidâ€? product technology has begun to put a damper on all that high joltage.
Smart fluids have already made inroads into the auto industry, in super-smooth shocks for high-end cars, including the 2004 Cadillac XLR and Chevrolet Corvette.
Magnetorheological fluid (MR fluid) is what gives vehicles that smoother ride. When a magnetic field is applied to minute iron particles suspended in a pourable liquid, the particles form a dense structure. The fluid then changes consistency to a semi-solid, changing back when the magnet is removed.
J. David Carlson is a physicist and engineering fellow at Lord Corporation, a Cary, N.C.-based company that develops MR fluids and devices. Lord's broad range of applications replaces intricate moving parts with smart fluids to dampen bad vibes.
Developed in the 1940s, MR fluids were a lab curiosity until the 1990s, as digital sensor technology made it possible to create smarter systems. This smart technology has appeared in Nautilus equipment, buildings and Delphi Automotive Systems' controllable shock absorbers, which debuted in the 2002 Cadillac Seville STS.
Carlson, who holds 56 patents relating to controllable materials, spoke with American Demographics recently about how MR fluids may improve our lives.
AD: How does an MR-fluid-based device work in a shock absorber?
DC: A sensor detects a change in conditions. It then tells the MR fluid device, which then reacts to counteract or dampen the motion or vibration.
AD: What products are you developing?
DC: Automotive, building-related and medical. We're working with a company in Germany that makes prosthetic limbs. We adapted a small shock absorber to be used in an artificial knee. Sensors measure forces, bending movements, knee angle and speed, field the information into a signal processor that feeds information into a microprocessor in the knee. It looks at these signals and determines whether a person is trying to walk on stairs, uphill or downhill. It compares what it sees to the overall gait and adjusts the shock absorber throughout the whole cycle, so it's always in the right position. The systems runs off of a couple of lithium batteries. It's almost a bionic knee.
AD: What are the comparative advantages of an MR fluid-based shock absorber?
DC: Standard passive shock absorbers in today's cars can't respond to changing conditions. They're set for one condition. MR fluid-based absorbers are faster and more reliable. They better counter pitch and roll, control vibration and the effects of bumps and how they're transmitted to the body. After a sudden step on the brake, you can limit how much you pitch forward. MR-fluid based valves respond to bumps much more quickly. When we design these, we look at how soft they get when you turn them off, not just how hard. That range gives you their power.
AD: What are the other benefits of using MR fluid-based devices?
DC: Automakers can run a car using electronics more easily and economically than mechanical forces. You would have a wheel at the dashboard that turns the sensor, and you have a wire that runs to the drive wheels, telling them what to do.
AD: What will we see in five or 10 years?
DC: Shock absorbers that use MR fluids can create forces to control or limit the movement of buildings in earthquakes. One of the problems with earthquakes is that it's hard to predict beforehand what kind of damping or controls you need to have in a building. With an MR shock absorber, you can control the vibrations that cause one floor to shift relative to the next floor. You could put shock absorbers in to absorb some of that unwanted energy so they don't build up and damage the structure of the building. Sometimes MR fluid dampers can let the ground move under the building, but if the vibrations become too large, it prevents the building from moving too far. MR fluid dampers have yet to be used in buildings in the U.S. People are far more cautious over here than in Japan in terms of building codes.
AD: What is your best market?
DC: The automotive market is huge. But it's tough getting into it because of all the testing and qualifications that are necessary.
AD: How big is the MR fluid and device market?
DC: Tens of millions of dollars and growing, but probably less than $50 million. It could be 10 times bigger in five years.
AD: What will spur that growth?
DC: We need to engineer these systems so that they are cheaper. That will make it possible to install them in more than just the high-end or high-performance vehicles. If I'm going to put this on my Saturn, cost becomes an issue.