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Presented by Zac Eichmeyer And BEMSS (BioElectromagnetic Student Society) 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 The 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 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= 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 •The V.P. Overview(subsystems) •Probes •Amplifiers •Oscillator •Bender •DAQ •Mechanical Manipulator 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 Sensing Probe Currently available probes MicroProbes, inc. Stainless steel Platinum Custom 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 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 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 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 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 BUDGET Item Quantity Cost Total Probes 3 128 $ (384.00) Bender 2 150 $ (300.00) Pre-amp 1 $ (100.00) Miscellaneous $ (200.00) Cost $ (984.00) Funding Resources UROP 1000 Total 24 Lock-in Amplifier Waveform generator BEMSS Expand it into two or three dimensions Computer controlled Mechanically threw the computer Improve sampling rate Min>50ms Integrate into BEMSS reasearch 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 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 Any Questions?