Nanotechnology gets even stranger

Nanotechnology is interesting.  When one starts to think that we have a reasonable knowledge of particle behavior, someone finds something new and interesting.  A basic assumption in thermodynamics is that objects change temperature (warming up or cooling down) at the same rate as a function of the environment of the particles.  Researchers at the Max Planck Institute of Biophysical Chemistry have predicted temperature change asymmetry based on mathematical models of confined nanoparticles [Ref. 1].  This modeling effort predicts that the motion of the warmer particles ends to bring them more quickly into the center of the probability distribution.  The researchers think that their results will improve the understanding of temperature change in nanoscale systems and provide insights into the Mpemba effect.  This phenomenon is the effect that warmer particles more quickly when its starting temperature is warmer.  They hope to confirm the theoretical results thought physical experiments. 

Researchers at the University of Arkansas have developed a graphene-based circuit, which they claim can produce clean power.  Their work appears to contradict Feynman’s theory that Brownian motion can not perform work.  The researchers contend that micron sized sheets of freestanding graphene move in a manner that is conducive to energy harvesting.    Their lab tests have indicated that freestanding sheets of graphene can generate an alternating current.  The researchers content that the thermal movement in the graphene is inherent in the material and not a result of temperature differential. 

Suhas Kumar of HP Labs, R. Stanley Williams at Texas A&M, and Ziwen Wang at Stanford have developed an electronic device that functions like a neuron.  The device combines resistance, capacitance, and Mott memristance. The most crucial part is the nanometers-thin niobium oxide (NbO2) layer.  (Note: Memristors are devices that hold memory based on the resistance of the current that has flowed through them. Mott memristors add the ability to incorporate any temperature-driven change in resistance.)  The structure of the material layers requires a high degree of precision.  The researchers developed the circuit through lengthy trial and error.

Most materials get thinner when they are stretched.  (A rubber band is a good example where it gets thinner as the length is elongated.)  Auxertic materials are different.  HELEN Gleeson, University of Leeds, has led research on auxertic materials that can be defined as material that also expands in one of the directions perpendicular to the elongation.  While these materials were originally formed in the 1970-80s, research into the development of synthetic auxetics ahs not been highly investigated.  The materials occur naturally in complex biomaterials.  Examples include human tendons.  Inorganic auxetics include copper, gold, and other face centric cubic materials.  When these materials are stretched, they undergo an internal reorganization, which forms voids that lowers the overall density.  The thoughts on potential applications include automotive windshields.  When an impact can cause a delamination between the various layers, incorporation of an auxertic could create an expansion where the base material undergoing an elongations and thinning.  This would increase the strength of the initial product.

As always, the world of nanotechnology provides unexpected insights into he property of materials at the nanorealm.

References:

  1. https://physicsworld.com/a/nanoparticles-warm-up-faster-than-they-cool-down/
  2. https://www.upi.com/Science_News/2020/10/02/Graphene-based-circuit-yields-clean-limitless-power/1571601661030/
  3. https://spectrum.ieee.org/nanoclast/semiconductors/devices/memristor-first-single-device-to-act-like-a-neuron?
  4. https://physicsworld.com/a/new-auxetic-material-stretches-the-limits/?

About Walt

I have been involved in various aspects of nanotechnology since the late 1970s. My interest in promoting nano-safety began in 2006 and produced a white paper in 2007 explaining the four pillars of nano-safety. I am a technology futurist and is currently focused on nanoelectronics, single digit nanomaterials, and 3D printing at the nanoscale. My experience includes three startups, two of which I founded, 13 years at SEMATECH, where I was a Senior Fellow of the technical staff when I left, and 12 years at General Electric with nine of them on corporate staff. I have a Ph.D. from the University of Texas at Austin, an MBA from James Madison University, and a B.S. in Physics from the Illinois Institute of Technology.

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