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

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?