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@PHDTHESIS{Nolten:229156,
author = {Nolten, Ulrich},
othercontributors = {Mokwa,Wilfried},
title = {{E}ntwicklung und {C}harakterisierung dehnungsbasierter
{K}raft- und {M}omentensensoren für medizinische
{A}nwendungen},
address = {Aachen},
publisher = {Publikationsserver der RWTH Aachen University},
reportid = {RWTH-CONV-144129},
pages = {VII, 203 S. : Ill., graph. Darst.},
year = {2013},
note = {Aachen, Techn. Hochsch., Diss., 2013},
abstract = {Force and torque sensors are widely used in robotics today.
But in medicine, many surgeons rather rely on their own
senses than on sensors. But also in this field –
especially in orthopedics – these sensors can assist the
surgeon. Fields of application are the long-term measurement
of loads in implants and the intra-operational measurement
of forces and torques. Force and torque sensor are based on
the following working principle: the elastic deformation of
a structure caused by external forces or torques is
measured. Therefore, the strain on the surface of the
structure is measured with strain gauges. During this work,
platinum strain gauges were manufactured and characterized
for different applications. Multiple strain gauges were
additionally grouped on sensor foils and were combined to
form measurement circuits. Moreover, the strain gauges on
the sensor foils can be aligned more precisely to each other
than single strain gauges. Application-specific sensor foils
therefore help to meet the demands of the measurement task
in the best possible way. The miniaturized strain gauges for
the sensor foil were produced on a polyimide substrate. They
have a gauge factor of k = 3 and show a linear temperature
coefficient of a = 2.5 • 10-3 K-1. The metal resistor has
a length of 1.23 mm and a width of 0.84 mm. Furthermore a
special assembly technique for the strain gauges was
developed. Additionally, the sensors can be sterilized with
hot steam for 30 times. Sensor foils for three different
applications were developed and tested. In the first
application, a 190 mm long milling tool for the removal of
femoral bone cement in revision total hip replacement was
realized. A sensor foil on the shaft measured the
deformation of the tool in reaction to the milling forces.
This information can be used for position correction in
navigated surgery. The second application is a sensor clip
for uniaxial force measurement on surgical tools. The sensor
clip can be attached on various instruments with a quick
mount. The sensor clip allows it to measure
intra-operational forces acting on the instrument. The
sensor clip is capable of measuring forces reproducibly.
This was shown on test structures. The third application is
a universal force and torque sensor. With this sensor it is
possible to measure forces in all spatial directions and
also measure the torques around the axes. The working
principle of this sensor was shown. Besides the platinum
strain gauges, piezoresistive silicon strain gauges were
designed and manufactured. The piezoresistors were
structured by reactive ion etching of the 2 µm thick device
layer of a SOI wafer. By this method, the resistor is fully
isolated by the buried oxide and the surrounding air.
Ultrasonic flip-chip bonding connects the sensors with gold
stud bumps to a flexible circuit board. On these circuit
boards, the piezoresistive strain gauges can be connected to
sensor foils again. The piezoresistive sensors have a gauge
factor of k = 70 and a temperature coefficient of a = 3.6
• 10-3 K-1.},
keywords = {Kraftsensor (SWD) / Kraftmessung (SWD) /
Dehnungsmessstreifen (SWD) / Piezowiderstandseffekt (SWD)},
cin = {611510},
ddc = {620},
cid = {$I:(DE-82)611510_20140620$},
typ = {PUB:(DE-HGF)11},
urn = {urn:nbn:de:hbz:82-opus-46672},
url = {https://publications.rwth-aachen.de/record/229156},
}
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