High-speed pressure clamp.
We built a high-speed, pneumatic pressure clamp to stimulate patch-clamped membranes mechanically. The key control element is a newly designed differential valve that uses a single, nickel-plated piezoelectric bending element to control both pressure and vacuum. To minimize response time, the valve body was designed with minimum dead volume. The result is improved response time and stability with a threefold decrease in actuation latency. Tight valve clearances minimize the steady-state air flow, permitting us to use small resonant-piston pumps to supply pressure and vacuum. To protect the valve from water contamination in the event of a broken pipette, an optical sensor detects water entering the valve and increases pressure rapidly to clear the system. The open-loop time constant for pressure is 2.5 ms for a 100-mmHg step, and the closed-loop settling time is 500-600 micros. Valve actuation latency is 120 micros. The system performance is illustrated for mechanically induced changes in patch capacitance.
Besch
Stephen R
SR
Center for Single Molecule Biophysics, 320 Cary Hall, SUNY at Buffalo, Buffalo, NY 14214, USA. sbesch@acsu.buffalo.edu
Suchyna
Thomas
T
Sachs
Frederick
F
D000818:Animals; D002462:Cell Membrane / Q000502:physiology; D025802:Electric Capacitance; D004867:Equipment Design; D006801:Humans; D040542:Mechanotransduction, Cellular; D018408:Patch-Clamp Techniques; D010812:Physical Stimulation / Q000295:instrumentation*; D011312:Pressure; D013997:Time Factors