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Piezoelectric effect

In 1880, Jacques and Pierre Curie discovered that a mechanical stress applied to the surfaces of various crystals (ex; quartz) results in generation of a corresponding electrical potential across the crystal. This behavior is known as the piezoelectric effect. By application of voltage across the crystal, mechanical strain of quartz generates. This effect is also known as converse piezoelectric effect.
Converse piezoelectric effect is the basis of our sensing technology. AT-cut quartz crystal is sandwiched by gold electrodes on both sides. Application of an alternative electric current across the quartz crystal results in thickness-shear mode oscillation of quartz crystal. This oscillation is highly stable, which contributes the decreasing the noise and increasing the sensitivity of our system.


Quartz Crystal Microbalance (QCM)

When molecules bound on oscillating quartz crystal, oscillating frequency decrease in proportional to binding amount of molecules on the surface. Sauebrey's equation is well known as basic relationship between the frequency changes and the binding amount on surface.


sensor fast > sensor mid > sensor slow

Delta F is the measured frequency change (Hz), F0 is the fundamental frequency of the quartz crystal (27x 106 Hz), Delta m is the mass change (g), A is the electrode area (0.049 cm2), rho q is the density of quartz (2.65 gcm-3), and mu q is the shear modulus of quartz
(2.95 x 1011 dyncm-2).
According to this equation, 1 Hz frequency change corresponds to 0.62 ngcm-2 of binding amount on surface. Highly fundamental resonance frequency (F0) can give highly frequency change (Delta F). We used 27 MHz of fundamental frequency quartz crystal that means our quartz crystal is about 30 times more sensitive than 5 MHz conventional quartz crystal microbalance.

Information obtained by AFFINIX experiments

Interaction analyses between each biomolecules (protein-protein, protein-DNA and protein-ligand, etc.) are essential to understand the function of biomolecules and evaluation of any biomaterials and biotechnological compound. AFFINIX series can analyze binding amount and its specificity, equilibrium constants and kinetic constants of biomolecular interactions. Binding (association) constant (Ka) and dissociation constant (Kd) are well known as equilibrium constants that indicate the strength of affinity between two molecules at the equilibrium state. Binding (association) rate (kon) and dissociation rate (koff) are well known as kinetic constants that indicate how fast its interaction occurs. kon and koff are also known as k1 and k-1.

1. Binding amount
2. Specific binding analysis
3. Equilibrium constant (binding constant (Ka) and dissociation constant (Kd))
4. Kinetic parameters (binding rate (kon) and off rate (koff))

Schematic image of interaction between molecule A and B is below. Molecule B is immobilized on QCM sensor surface, and molecule A that is in solution binds onto molecule B-immobilized surface.

Figure 1 Figure 1