Molecular Electronic Transducers


Molecular Electronic Transducers

Molecular Electronic Transducers (MET) are a class of inertial sensors (which include accelerometers, gyroscopes, tilt meters, seismometers, and related devices) based on an electrochemical mechanism. METs capture the physical and chemical phenomena that occur at the surface of electrodes in electrochemical cells as the result of hydrodynamic motion. They are a specialized kind of electrolytic cell designed so that motion of the MET, which causes movement (convection) in the liquid electrolyte, can be converted to an electronic signal proportional to acceleration or velocity. MET sensors[1] have inherently low noise and high amplification of signal (on the order of 106).

Contents

History of Molecular Electronic Transducers

MET technology had its origins in the 1950s,[2][3][4][5] when it was discovered that very sensitive, low-power, low-noise detectors and control devices could be made based on specially designed electrochemical cells (which were referred to as “solions”, derived from the words solution and ions). Up through the 1970s, the US Navy and others supported development of solion devices for sensitive sonar and seismic applications, and a number of patents were filed.[6] However, early solion devices had a number of serious problems such as lack of reproducibility and poor linearity, and practical production of devices was abandoned in the US and progress languished for decades.

However, fundamental physics and mathematical studies of the underlying electrochemical and fluid flow dynamical processes continued, principally in Russia, where the field came to be known as “molecular electronics”.[7] In recent years both mathematical modeling and fabrication capabilities improved dramatically, and a number of high-performance MET devices have been developed.[8]

Principles of Operation

At the heart of a MET device are two (or more) inert electrodes at which a reversible redox reaction occurs, which does not involve either plating of a metal or evolution of a gas. Typically, the aqueous iodide-triiodide couple is used:

3 I- → I3- + 2 e- anode reaction

I3- + 2 e- → 3 I- cathode reaction

When a voltage in the range of ~ 0.2 to 0.9V is applied across the electrodes, these two reactions occur in a continuous fashion. After a short time, the electrochemical reactions deplete the concentration of triiodide ions [I3-] at the cathode and enrich it at the anode, creating a concentration gradient of [I3-] between the electrodes. When the cell is motionless, the electrochemical reaction is limited by the diffusion of I3- to the cathode (a slow process), and the current dies down to a low steady-state value.

Motion of the device causes convection (stirring) in the electrolyte. This brings more I3- to the cathode, which in turn causes an increase in the cell current proportional to the motion. This effect is very sensitive, with extremely small motions causing measurable (and low noise) inertial signals.

In practice, the design of the electrodes to create a device with good performance (high linearity, wide dynamic range, low distortion, small settling time) is a complex hydrodynamic problem.

Advantages of MET sensors

The main advantage of MET sensors over competing inertial technologies is their combination of size, performance and cost. MET sensors have performance comparable to fiber optic gyroscopes (FOGs) and ring laser gyros (RLGs) at a size close to that of MEMS sensors, and at potentially low cost (in the tens to hundreds of dollars range, in production). In addition, the fact that they have a liquid inertial mass with no moving parts makes them rugged and shock tolerant (basic survivability has been demonstrated to >20 kG); they are also inherently radiation hard.

Applications

Depending on the configuration of the MET device, a variety of inertial sensors can be produced including:

References

  1. ^ http://www.mettechnology.com
  2. ^ R. M. Hurd and R. N. Lane, “Principles of Very Low Power Electrochemical Control Devices”, J. Electrochem. Soc. vol.104, p. 727 – 730 (1957).
  3. ^ I. Fusca, “Navy wants industry to share burden of solion development”, Aviation Week, vol.66, #26, p.37, 1957.
  4. ^ A. F. Wittenborn, “Analysis of a Logarithmic Solion Acoustic Pressure Detector”, J. Acoust. Soc Amer. vol.31, p. 474 (1959).
  5. ^ C. W. Larkam, “Theoretical Analysis of the Solion Polarized Cathode Acoustic Linear Transducer”, J. Acoust. Soc. Amer. vol.37, p. 664-78 (1965).
  6. ^ See for example US Patents 3,157,832; 3,223, 639; 3,295,028; 3,374,403; 3,377,520; 3,377,521; and 3,457,466
  7. ^ N. S. Lidorenko et al., Introduction to Molecular Electronics [in Russian], Énergoatomizdat, Moscow (1985).
  8. ^ see www.mettechnology.com

Wikimedia Foundation. 2010.

Look at other dictionaries:

  • Nanowire — Part of a series of articles on Nanoelectronics Single molecule electronics …   Wikipedia

  • automata theory — Body of physical and logical principles underlying the operation of any electromechanical device (an automaton) that converts information input in one form into another, or into some action, according to an algorithm. Norbert Wiener and Alan M.… …   Universalium

  • ultrasonics — /ul treuh son iks/, n. (used with a sing. v.) the branch of science that deals with the effects of sound waves above human perception. [1930 35; see ULTRASONIC, ICS] * * * Vibrational or stress waves in elastic media that have a frequency above… …   Universalium

  • Sound from ultrasound — Contents 1 Parametric array 2 Applications 2.1 Commercial advertising …   Wikipedia

  • Medical ultrasonography — This article is about using ultrasound to image the human body. For imaging of animals in research, see Preclinical imaging. Sonography redirects here. For the tactile alphabet called sonography , see Night writing. Medical ultrasonography… …   Wikipedia

  • analysis — /euh nal euh sis/, n., pl. analyses / seez /. 1. the separating of any material or abstract entity into its constituent elements (opposed to synthesis). 2. this process as a method of studying the nature of something or of determining its… …   Universalium

  • Ceramic engineering — Simulation of the outside of the Space Shuttle as it heats up to over 1,500 °C (2,730 °F) during re entry into the Earth s atmosphere Ceramic engineering is the science and technology of creating objects from inorganic, non metallic… …   Wikipedia

  • Self-reconfiguring modular robot — Modular self reconfiguring robotic systems or self reconfigurable modular robots are autonomous kinematic machines with variable morphology. Beyond conventional actuation, sensing and control typically found in fixed morphology robots, self… …   Wikipedia

  • Electric motor — For other kinds of motors, see motor (disambiguation). For a railroad electric engine, see electric locomotive. Various electric motors. A 9 volt PP3 transistor battery is in the center foreground for size comparison. An electric motor converts… …   Wikipedia

  • Frequency comb — A frequency comb is the graphic representation of the spectrum of a mode locked laser. An octave spanning comb can be used for mapping radio frequencies into the optical frequency range or it can be used to steer a piezoelectric mirror within a… …   Wikipedia