The V.P. P.D.R. (Vibrating Probe)

1. The V.P. P.D.R.(Vibrating Probe) Presented by ZacEichmeyer And BEMSS (BioElectromagnetic Student Society)

2. What's a Vibrating Probe • The Vibrating Probe is a device which detects current densities by • Vibrating a Probe about a micron in amplitude • Using a Piezo-Electric bender/oscillator • The Probe is fed into a lock in amplifier which allows the probe to be sampled at the same frequency as the bender • Reducing Noise, and giving a voltage reading at the max of its amplitude

3. The Vibrating Probe

4. Why build a Vibrating Probe • The Vibrating Probe is an instrument capable of measuring current densities up to 10 nA/cm2 • It is most commonly used to detect Current densities in biological mediums • Will be used in conjunction with other research that BEMSS is doing • Best way of getting sensitive data with out disturbing the cell

5. Project Definition • This Project will consist of designing, building, implementing and testing of a Vibrating Probe • This will consist of • Design the Probe • Finding the appropriate Oscillator • Piezo-electric is most applicable • Interfacing the Osillator with the probe • Pre amp in series with a Lock-in amplifier • Building the appropriate structure for implemention • Making a data Acquisition systems=

6. Project Goals • To be able to measure current densities <100 mA/cm2 • To eliminate/control extraneous noise • To build the appropriate test setup to implement the probe with a microscope • Implement into current BEMSS research • Measure current densities in other biological samples

7. Project Overview (Top Down) • The V.P. Overview(subsystems) • Probes • Amplifiers • Oscillator • Bender • DAQ • Mechanical Manipulator

8. V.P. Subsystems and DiversThe Probes • Two Probes • Ref Probe • Used to find a Common to measure off of • Placement is the most important Driver • Sensing Probe • Used to find the Potential in a given medium • Drivers • Length to mass ratio • directly influences what you can detect • Impedance of the probe • Lower the impedance the higher the resolution • Material • Directly influences

9. V.P. Subsystems and DiversThe Probes Con't • Sensing Probe • Currently available probes • MicroProbes, inc. • Stainless steel • Platinum • Custom

10. V.P. Subsystems and DiversThe Amplifiers • Two Types of Amplifiers • Pre-Amp • This conditions the signal to feed it into the Lock-in Amp • The main driver is low noise • Lock-in Amplifier • Needs to lock the signal from the probes to the oscillator • So to read the probe at its max amplitude • Needs to be able to output out to a DAQ system • Lock-in Amplifiers are expensive, might institute a PLL circuit instead

11. V.P. Subsystems and DiversThe Oscillator • The Oscillator needs to provide a stable signal in the range of 150 Hz to 1 kHz at 10 Vpp • This covers the frequency range of available probes • Can use the Wave Generators availble

12. V.P. Subsystems and DiversThe Bender • The Bender needs to be able to take an electrical signal and convert it to a mechanical force • Piezoelectric actuators are best suited for this • Allow a high degree of control • Many currently available to buy commercially • Drivers • Needs to be precise • Deflection of more than 1 mm

13. V.P. Subsystems and DiversDAQ and Test setup • The Data Acquisition System drivers • A/D conversion (Measure voltage) • Data logging capabilities • Needs to sample at least every 50 ms • Test Setup Drivers • Needs to be mechanically stable • Any vibration will be detected as extraneous noise • Needs to be precise • We are measuring Currents/Voltages on cells that are on the scale of 10mm • Needs to mount to a microscope setup • To be implemented with the BEMSS group later

14. V.P. Subsystems and DiversThe Interconnections • Mechanical • Between the bender and the probe • Needs to be sufficiently rigid to translate the bender’s vibration to the probe • Mechanical Manipulator • To move the Probe around on a sample • Needs to be rigid and thermally/electircally isolated • Electrical • NOISE!!! • Noise is the greatest problem/driver here • Keep connections short, don’t make loops • Connection from VP to Pre-Amp is the most vulnerable

15. Budget

16. Schedule

17. Expandability and the Future • Expand it into two or three dimensions • Computer controlled • Mechanically threw the computer • Improve sampling rate • Min>50ms • Integrate into BEMSS reasearch

18. Conclusion • The VP is an instrument capable of measuring current densities as low as 10 mA/cm2 • Used primarily for measurements in biological mediums • Consists of 5 main subsystems • Probes • Amplifiers • Oscillator • Bender • DAQ

19. References • Pictures: Nuccitelli, Jaffe, “AN ULTRASENSITIVE VIBRATING PROBE FOR MEASURING, STEADY EXTRACELLULAR CURRENTS”, www.jcb.org • UMASS Vibrating Probe Facility- http://marlin.bio.umass.edu/biology/kunkel/conte/polarized-probes.html • Information, background and resource • Nuccitelli, Jaffe, “AN ULTRASENSITIVE VIBRATING PROBE FOR MEASURING, STEADY EXTRACELLULAR CURRENTS”, www.jcb.org • “A simple method for preparing a Vibrating Probe” T Nakagawa, http://pcp.oxfordjournals.org

20. Any Questions?