Twisting and Stretching
Single Molecules
Adding a twist to DNA
<< previous
next >>

Micro Pipette Sensors

Micro pipette Setup

Micropipette Sensors are made using very thin glass capillary needles typically one micron thin and a millimeter long. These flexible devices are very easily bent by a small force pulling them perpendicularly away from their axis [1]. To build such a sensor requires a means to detect the small displacement of the needle: this may be done optically by analyzing the video image of the needle or by using an optical fiber [2] as the needle and imaging the light spot at the end of the needle on a four-quadrant diode detector [3].

The force sensitivity of a Micropipette Sensor is related to its stiffness. Typically on the order of 10-5 N/m, or 10 pN per micron of dislacement. A very common error consists in saying that the best sensor is the one with the smallest stiffness. We shall see that the best sensor (in term of signal to noise) in in fact the smallest device. Since the Micropipette is rather long compared to other sensors, they are usually not the best.

A. Ishijima, Y. Harada, H. Kojima, T. Funatsu, H. Higuchi, T. Yanagida,
Biochem. Biophys. Res. Commun. (1994) 199-2 p.1057 PubMed CrosRef
2DNA: An extensible molecule
P. Cluzel, A. Lebrun, C. Heller, R. Lavery, JL. Viovy, D. Chatenay, F. Caron,
Science (1996) 271-5250 p.792 Science publications CrosRef
3Mechanical separation of the complementary strands of DNA
B. Essevazroulet, U. Bockelmann, F. Heslot,
Proc. Natl. Acad. Sci. U. S. A. (1997) 94-22 p.11935 PNAS publications CrosRef
For further information please contact picotwist.