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

The V.P. C.D.R. (Vibrating Probe). Presented by Zac Eichmeyer And BEMsS (BioElectromagnetic student Society). What's a Vibrating Probe (V.P.)?. The V.P. is an instrument capable of measuring current densities in a biological medium Capable of measuring 10 nA/cm 2

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

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  1. The V.P. C.D.R.(Vibrating Probe) Presented by Zac Eichmeyer And BEMsS (BioElectromagnetic student Society)

  2. What's a Vibrating Probe (V.P.)? • The V.P. is an instrument capable of measuring current densities in a biological medium • Capable of measuring 10 nA/cm2 • It was developed in the 70’s to measure current pulses from an Oocyte • Non-Destructive measurements • Can measure activities in live cells • Offers an order of magnitude increase from current detection methods, and is more versatile than dyes

  3. The Vibrating Probe In Action

  4. How does the V.P. Work? • The V.P. works by vibrating a high impedance probe horizontally ~10mm • The vibration is controlled by a Piezoelectric Actuator • The Probe is connected to a Preamplifier which conditions the signal for the Lock-In Amplifier • The Lock-in amplifier locks the probes measurement to that of its vibration so to only read current density at its max displacement • Reducing Noise, and giving a voltage reading at the max of its amplitude • The data is then collected via a data logger and fed into a computer for analyzing

  5. Project Definition • The V.P. Requirements: • The probe • High impedence, greater than 5 MW • Low length to mass ratio • Piezoelectric Actuator (the bender) • Operate between ± 45V • Bend at least 30mm • The Lock-in Amplifier • Lock on to a 150 Hz – 1kHz signal • The Pre-Amp • Low Noise

  6. Project Definition, Con't • The DAQ • Capable of sampling faster than the vibration frequency • <1 kHz max • The Oscillator • Capable of driving a Piezoelectric Actuator at a frequency less then 1kHz • The Mechanical Manipulator • Connects the probe to the microscope • Rigid • Have 1 degree of motion (up and down) • Thermally and electrically neutral

  7. Project Goals • To be able to measure current densities <100 nA/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 • Track Ion concentrations as they relate to Neutrophils

  8. Project Overview (Top Down) • The V.P. Overview(subsystems) • Probes • Piezoelectric Actuator (Bender) • Pre Amp • Lock In Amplifier • Oscillator • DAQ • Housing • Mechanical Manipulator

  9. Project Overview (Top Down)

  10. V.P. Subsystems and DiversThe Probes • Two Probes • Ref Probe • Used to find a Common • Sensing Probe • Used to find the Potential in a given medium • Construction: • Plate probe in gold • Gold is more bio-friendly than steel • Connect to Housing • Drivers • Length to mass ratio • Impedance of the probe • Material

  11. V.P. Subsystems and DiversThe Probe Selection • Sensing Probe • The Elgiloy Stainless Steel Microelectrodes • Dimensions (D x L) 225mm x 80mm • Impedence is 12 MW • Tip Diamter, 1-2 mm

  12. V.P. Subsystems and DiversThe Piezoelectric Acutator • A Piezoelectric Actuator is a device which can deflect when given a voltage • Will use as the vibration device • Capable of vibrating • Between 100 Hz to 1 kHz • Amplitude of ± 10 mm • Operate with a Vpp of 60 Volts • Must be Mountable onto the microscope test setup

  13. V.P. Subsystems and DiversThe Piezoelectric Acutator • Selection: Physik Instumente-PICMA® Ceramic-Encapsulated Piezo Bender Actuator, PL112.10 • Size (L x W x T): 17.8 x 9.6 x .65 [mm] • Deflection: 160 mm (nominal) • Input Voltage Nominal Voltage ± 45 V • Max Voltage ± 90 V

  14. V.P. Subsystems and DiversThe Pre Amplifiers • Pre-Amplifier Drivers • This conditions the signal to feed it into the Lock-in Amp • Low Noise • Differential input • High Input Impedance • At least a 10x gain • Selection: Model 100 Preamplifier • Available at Applicable electronics

  15. V.P. Subsystem and DriversThe Lock In Amplifier • Lock-in Amplifier • Needs to lock the signal from the probes to the oscillator • 150 Hz to 1 kHz ref input • Needs to be able to output out to a DAQ system • Selection: Stanford Research Systems • Model SR810 DAP Lock-In Amplifier

  16. V.P. Subsystems and DiversThe Oscillator • The Oscillator needs to provide a stable signal in the range of 150 Hz to 1 kHz at 45 Vpp • The probe will need to vibrate at its resonance frequency • This range covers all possible frequencies for the probes • Must be relatively stable • Not crucial because the Lock In amplifier will compensate • Selection: Hewlett Packard Model 204C Oscillator

  17. V.P. Subsystem and DriversThe Housing • Holds the Probe and allows the actuator to vibrate the probe • Requirements • Electrically and thermally neutral • Rigid • Allow light through • Selection: • Custom Made according to specification • Material: Lucite

  18. V.P. Subsystem and Drivers Mechanical Manipulator • Test Setup Drivers • Needs to be mechanically stable • Any vibration will be detected as extraneous noise • Needs to be precise • Accurate to ~5 mm • Needs to mount to a microscope setup

  19. V.P. Subsystems and DiversDAQ • The Data Acquisition System • A/D conversion (Measure voltage) • Data logging capabilities • Needs to sample at least every 10 ms • The HOBO Data Logger • HOBO U12 Temp/RH/2 External Channel Logger • USB connection to Computer • Analog Voltage measurement • 12 bit resolution (.6mV) • 0-2.5 v sensor range • Accuracy 1%

  20. Test Plan • Three Phases : Preliminary, Intermediate and Final • Preliminary • Probes • Measure Impedance • Measure Mass • Piezoelectric Actuator • Verify vibration modes • Oscillator • Verify stability and range • DAQ • Connect to computer and start to log • Mechanical manipulator • Connect to Microscope, show degree of freedom • Lock-in Amplifier • Verify its ability to lock onto a signal

  21. Test Plan con't • Intermediate: • Mechanical • Housing • Make sure everything attaches snuggly • Verify the vibration mode with the Probe • Show light can still get through • Mechanical manipulator • Attach housing, show stability • Electrical • Pre-Amp • Verify the gain • Show stability • Probes • Attach to Pre-amp • Calibrate (as shown in the appendix)

  22. Test Plan Con't • Final phase: • Mechanical • Attach everything to the microscope test setup • Show functionality • 3 degrees of movement (2 by the microscope slide) • Electrical • Connect the Pre-amp and Oscillator to Lock in Amp • Verify its sampling correctly • Connect the Lock in amp to the DAQ • Verify its outputting accurately • Measure well known cell actions • To prove calibration • Start measuring voltages off of live cells

  23. Planned Delverables • Mile Stone 1 Deliverables • Construct housing • Make and Prep the Probes • Complete all of the preliminary testing phase • Milestone 2 Deliverables • Complete all of the intermediate testing phase • Physically attach all pieces together • Begin Live cell tests • Design Expo • A fully working VP system, that can be demonstrated live

  24. Schedule

  25. Budget

  26. 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

  27. Conclusion • The VP is an instrument capable of measuring current densities as low as 10 nA/cm2 • Used primarily for measurements in biological mediums • The V.P. Overview(subsystems) • Probes • Piezoelectric Actuator (Bender) • Pre Amp • Lock In Amplifier • Oscillator • DAQ • Housing • Mechanical Manipulator

  28. 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 • Reid, Nuccitell, Zhao, “Non-invasive measurement of bioelectric currents with a vibrating probe” Nature Protocols, Vol 2, #3, 2007, p 661-669 • 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 • Reid, Nuccitell, Zhao, “Non-invasive measurement of bioelectric currents with a vibrating probe” Nature Protocols, Vol 2, #3, 2007, p 661-669

  29. Any Questions?

  30. AppendixCalibration

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