vibration kills and other lessons

8/13/2019 vibration kills and other lessons

1/21

“Vibration Kills” and otherLessons from the Trenches

Hal Amick & Michael Gendreau


2/21


3/21

O tical Devices

“Jiggle” or blurring of images – Impairment of visualobservationMisalignment of sequential photographic images

Misinterpretation by visual processing software

Electron Beam Devices –measurement errors

Probe-Type Devices

Long-beam-path DevicesBeams deflected , often causing energy loss or misalignment


4/21

• -

device

• A surgeon’s vibration-induced nausea (durings ine sur er … ouch!

• Lab mice and vibration-induced startle

•


5/21

Serendipitous discoveryof life-saving medical device


6/21

• Stent: A slender catheter

inserted into a bloodvessel, to provide supportafter balloon an io lastor to facilitate expansionof the vessel diameter

• Stenosis: Theconstriction or narrowing

vessel after angioplastyor insertion of stent


7/21

• Balloon angioplasty developed to unclog coronary

arteries• A certain fraction of them collapsed or grew inward to

• Stents introduced to keep them open

• Artery grew through the “cage” of the stent and inwardrom ere

• Several drugs have been developed to fight this• A researcher discovered that one of them could be

delivered directly to the artery by coating the stent


8/21

- • Several million drug-eluting stentshave been “installed”

• The drug is applied to the stentskeleton

• A chemical “trick” is employed torelease the drug over time

• The “trick” is the result of aserendipitous observation of a

chemical gradient that could beexploited to deliver the drug

• The researcher repeated theexperiment a few months ago,artificially increasing the floor

v ra on o gener c a eve s(VC-A) – The chemical gradient did not

form. He would not have made


9/21

A surgeon’s

vibration-induced nausea

oops!


10/21

• Some t es of

surgery requiremicrosco 10x to 50x) – – Spine


11/21

•

four operating rooms, two dedicated tomicrosur er , usin floor-mountedmicroscopes

– One Leica, one Zeiss• “Occasionally” there are vibrations which

cause the image to jiggle• One of the surgeons is about to start

refusing patients.


12/21

…• , ,

• The “typical” vibration environment in these OR’sis below VC-A OR criterion is 2*VC-A

• Footfall below VC-A• -• “Problem” occurs a few minutes at a time, a few

times a da• One surgeon routinely experiences nausea

durin the “ roblem”


13/21

Routine Floor Measurements(why such a problem?)

- -

10000during vibration inducedvisibility interference

w ithout vibration inducedProblem

1000

i t y , µ

m / s

Perception

VC-A

10

100

r m s

V e

l o c

1

1 1.3 1.6 2 2.5 3.2 4 5 6.3 8 10 12.5 16 20 25 31.5 40 50 63 80

One-Third Octave Band Center Frequency, Hz


14/21

Compare Floor and Eyepiece(in Narrowband) Over 100 arc-sec

at 50mm

1000

w/ Interference

w/o Interference

1000

w / Interference

w /o Interference

100

i t y ,

u m

/ s 100

t y , u m

/ s12 Hz

24 Hz

1 r m s

V e

l o 10

r m s

V e

l o c

i

0.1 0.1

Frequency, Hz0 10 20 30 40 50

Frequency, Hz


15/21

Compare Floor and Eyepiece(in Narrowband)

1000

Eyepiece

Floor

1000

Eyepiece

Floor

100

t y , u m

/ s100

i t y , u m

/ s

10

r m s

V e

l o c

i10

r m s

V e l o c

0.1 0.10 10 20 30 40 50

Frequency, Hz

0 10 20 30 40 50

Frequency, Hz


16/21

…•

– 8-12 Hz, 18-21 Hz, in this configuration

• er e v r r e

equipment (12.0 Hz and harmonics) only-• Improve the vibration isolation on the

mechanical equipment• Was VC-A adequate?


17/21

Cell Death

Patch-Clamp Experimentation


18/21

Whole-Cell Patch Clamp Work(e.g., Electrophysiology)

•

electrostatically “attached” to a cell – Can in ect material into cell – Can remove material

– Can monitor cell – Can stimulate cell

• Excessive vibration can dama e theattachment, causing leakage and celldeath


19/21

– • Excessive vibration can

amage an t us ce sduring electrophysiologyexperiments. –

ectrop ys o ogyprobe (1 microndiameter at contact)

setup. Movie shows cell deathafter nearby “heel drop” on

floor • xcess ve v ra on can

prevent important discoveriesfrom happening –

Living muscle cell(40 micron x 140micron)

process “just doesn’t work”and not realize it didn’t workbecause of vibration

Images and movies courtesy Dr. Harold Spurgeon, NIH


20/21

• Most criteria used by acousticians and vibrationconsu an s are ase upon spass ona e parame ers

• Some criteria associated with biolo ical and medicalresearch communities deal with life-and-death issues – Test specimens – Ultimate beneficiaries of research

• In some cases, we know conceptually what to avoid, butdon’t have a criterion – The “easy out” is to be conservative—use VC-A – Value Engineering (VE) is challenging uses of conservatism


21/21

Questions?

Documents

vibration kills and other lessons