Minus K Technology

Minus K Technology Helps Alternating Current Scanning Tunneling Microscopes (ACSTM ) Illuminate Unprecedented Details of Single Molecule Chemical Behavior

Developed in the early 1990s by Prof Paul Weiss, the nano-pioneering Director of the Weiss Group, a nanotechnology research unit at UCLA's California NanoSystems Institute, the ACSTM's single-molecule measurement techniques have illuminated unprecedented details in chemical behavior, including observations of the motion of a single molecule and even the vibration of a single bond within a molecule.

"The ACSTM enables interactions within and between molecules to be designed, directed, measured, understood, and exploited," said David McMillan, lead technician at the Weiss Group. "The group examines how these interactions influence chemistry, dynamics, structure, electronic function, and other properties. "

The Challenge:
To achieve these nano-level chemical and spectroscopic data sets requires that the ACSTM be positioned in an ultra-stable operating environment, one free of low-frequency vibrations. "The lab was using almost exclusively optical tables on pneumatic isolation," said McMillan. "One of our big problems has been space constraint. We needed smaller pneumatic optical tables to fit, but as the air tables get smaller, their vibration isolation performance diminishes."

"Space was not the only issue," continued McMillan. "Our lab was occasionally moved to different locations at UCLA. In 2009, we were located on the sixth floor of a steel-structure building that had significant movement creating low-frequency vibrations. Under these conditions, the pneumatic tables were highly perturbable, and difficult to get vibration isolation and thermal stability. We were not able to functionally run our microscopes using the air tables. So, we began looking for another vibration isolation solution."

The Solution:
The team looked at both an active vibration isolation unit as well as a Minus K Negative-Stiffness system. "We compared the two systems," explained McMillan "and the Negative Stiffness system performed better with the frequencies of our concern, which were the lower frequencies caused by the movements of the building - between 10 and 24 hertz. Compared to the optical tables, the Minus K Negative-Stiffness isolator performed significantly better. Where before, we could not even use our microscopes with the air tables, when we put in the Negative-Stiffness isolator we had full vibration and thermal functionality." "Over the past four years we have put six Negative-Stiffness isolation systems into the lab," McMillan concluded, "and since then, we have relocated into quarters with less movement. Although we still have some air tables in use, our staff and graduate students prefer the Negative-Stiffness isolators."

Full article here: https://minusk.com/content/in-the-news/R&D_0616.html?newsletter-lp

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