Interview with David Platus, President and Founder
of Minus K Technology, Inc. and principal inventor
of Negative-Stiffness Mechanism vibration isolation
PSD: Tell us about Minus K Technology.
DP: Minus K Technology was founded in 1993 to develop,
manufacture and market state-of-the-art vibration isolation
products based on the company's patented Negative-Stiffness
(NSM) technology. The company's products are used in a broad
spectrum of applications including photonics, nanotechnology,
biological sciences, semiconductors, materials research,
zero-g simulation of spacecraft and high-end audio.
PSD: What is Negative-Stiffness vibration isolation?
DP: Negative-Stiffness isolators employ a completely mechanical
concept in low-frequency
vibration isolation. It is really quite unique to the field
of laser/optical systems. In particular, the transmissibility
? that is the vibrations that transmit through the isolator
relative to the input vibrations ? is substantially improved
over air systems and active isolation systems.
PSD: How does Negative-Stiffness vibration isolation work?
DP: Negative-Stiffness isolators typically use three isolators
stacked in series: a tilt-motion isolator on top of a horizontal
motion isolator on top of a vertical motion isolator. Vertical
motion isolation is provided by a stiff spring that supports
a weight load, combined with a Negative-Stiffness mechanism.
The net vertical stiffness is made very low without affecting
load-supporting capability of the spring. Beam columns connected
in series with the vertical-motion isolator provide horizontal-motion
PSD: What specific performance results does Negative-Stiffness
vibration isolation deliver?
DP: The isolators adjusted to 0.5 Hz achieve 93 percent
isolation efficiency at 2 Hz, 99 percent at 5 Hz, and 99.7
percent at 10 Hz.
PSD: What advantage do Negative-Stiffness systems have
over air tables?
DP: Negative-stiffness systems provide substantially lower
natural frequencies vertically and horizontally enabling
them to isolate lower frequency vibrations and provide improved
isolation over the entire range of building and floor frequencies.
Further, the need for pneumatics and electric power is eliminated
with Negative-Stiffness systems.
PSD: How does Negative-Stiffness compare to active isolation
DP: Active isolation systems start isolating as low as
0.7 Hz. But, because active systems run on electricity,
(NSM does not require electricity) they can be negatively
influenced by problems of electronic dysfunction and power
modulation, which can interrupt scanning. Active systems
also have a limited dynamic range which is easy to exceed,
causing the isolator to go into positive feedback and generate
noise underneath the equipment. Although active systems
have fundamentally no resonance, their transmissibility
does not roll off as fast as NSM isolators.
PSD: Has the photonics industry embraced Negative-Stiffness
DP: Negative-Stiffness vibration isolation has become a
growing choice for laser and optical applications. Not only
is it a highly workable vibration solution, its cost is
significantly less ? up to one third the price compared
to active and traditional passive systems ? making it an
economical solution to cost-conscious administrators.
PSD: What three Minus K achievements are you most proud
DP:1. Being selected to provide the isolation system for
ground testing of the James Webb Space Telescope (JWST)
and other major NASA and DOD programs. 2. Solving a customer's
vibration problem with a TEM on the fifth floor out of spec
between 1.5 and 2.5 Hz. 3. Getting rave reviews from audiophiles
who are "blown away" by the improved sounds from
their audio systems and passing jump tests on wood frame