1. science
2. medicine
3. surgery

IEEE SENSORS JOURNAL, VOL. 13, NO. 5, MAY 2013
1541
MEMS-Based Intraoperative Monitoring System for
Improved Safety in Lumbar Surgery
Xing Liu, Hui Chen, Qing-An Huang, Senior Member, IEEE, and Darrin J. Young, Member, IEEE
Abstract— This paper presents the design and characterization
of a microelectromechanical system (MEMS)-based intraoperative monitoring system for improving lumbar surgery safety.
A MEMS pressure-sensing module is designed and incorporated
into a nerve root retractor tip to directly monitor pressure exerted
on a nerve root during a lumbar surgery. Animal experiments are
conducted for intraoperative pressure monitoring to investigate
effects of nerve root retraction during a surgery. Amplitude
and latency of electrophysiological response of a nerve root
are measured during different time intervals after retraction
under various retraction magnitude and duration conditions.
Correlation between exerted pressure on a retracted nerve
root and its electrophysiological response is investigated. The
relationship between intraoperative pressure and alteration of
neural tissue structure is analyzed by morphological observation.
Experimental results indicate that a nerve root injury is strongly
related to the magnitude and duration of its retraction. The
prototype MEMS-based intraoperative monitoring system can
potentially alert surgeons about risk factors associated with
nerve root injury during a lumbar surgery as well as provide
critical surgical guidelines. The system can also serve as a basis
for implementing an intelligent robotically controlled closed-loop
lumbar surgical operating system in the future.
Index Terms— Iatrogenic nerve root injury, intraoperative
monitoring system, intraoperative pressure monitoring, lumbar
surgery, silicon pressure sensor.
I. I NTRODUCTION
A
LARGE population suffers from chronic low back pain
due to various medical reasons. With rapid development
of medical technology, an increasing number of patients, who
are unaided by the conservative therapies alone, have begun
to resort to lumbar surgery for a rapid effective resolution
of symptoms [1]. However, this type of surgery has associated potential risks of iatrogenic neurological damage due to
the surgical site being too close to the nerve root [2], [3].
Manuscript received September 17, 2012; revised December 1, 2012;
accepted January 21, 2013. Date of publication March 20, 2013; date of
current version March 27, 2013. This work was supported in part by the
Foundation of Science and Technology Commission of Nanjing, China under
Grant 201001093, and the National Natural Science Foundation of China
under Grant 61136006. The associate editor coordinating the review of this
paper and approving it for publication was Prof. Paul C.-P. Chao.
X. Liu and Q.-A. Huang are with the Key Laboratory of MEMS of
Ministry of Education, Southeast University, Nanjing 210096, China (e-mail:
[email protected]).
H. Chen is with the Medical College, Southeast University, Nanjing 210009,
China.
D. J. Young is with the Department of Electrical and Computer Engineering,
University of Utah, Salt Lake City, UT 84112 USA.
Color versions of one or more of the figures in this paper are available
online at http://ieeexplore.ieee.org.
Digital Object Identifier 10.1109/JSEN.2013.2243141
Fig. 1.
Schematic of nerve root retraction during a lumbar surgery.
Keeping away from an inadvertent contact or damage by
surgical instruments, the nerve root would typically be pulled
outside the surgical corridor by using a nerve root retractor
as depicted in Fig. 1. The degree of a nerve root retraction
typically depends on a surgeon’s manual manipulation. An
excessive nerve root retraction can cause neurological injury,
thus resulting in a postoperative symptom [4]–[6].
Electrophysiological monitoring is introduced into the
surgery for avoiding iatrogenic neurological injury [7]–[9].
To reveal the physiological integrity of the nerve root during
operation, the surgical procedure has to be interrupted and
the electrical stimulation is applied on the nerve root to
obtain electromyography (EMG) signals. The measurement
would be repeated multiple times during a surgery to alert the
surgeon to any deterioration before irreversible neural injury
of the nerve root occurs. The electrophysiological monitoring
can significantly increase treatment cost and operation time.
In most lumbar surgeries, such monitoring procedures are
not warranted [7], [10]. It is, therefore, highly desirable to
develop an effective, low cost and user-friendly intraoperative
monitoring system to address aforementioned concerns.
MEMS technology has been widely employed for medical
applications [11]–[16], greatly improving the functionality
and performance of surgical devices, lowering risk to improve
surgical outcomes, and providing real-time feedback on the
operations [17]–[19]. In this paper, a MEMS-based intraoperative monitoring system design, implementation, and characterization for improving lumbar surgery safety is presented. The
MEMS-based intraoperative monitoring would be beneficial
for monitoring neural function integrity of the nerve root
without interrupting the surgical procedure. A MEMS pressure
sensing module is designed and incorporated into a prototype
nerve root retractor to directly monitor pressure exerted on
a nerve root during a lumbar surgery. Animal experiments
have been conducted for intraoperative pressure monitoring
to investigate effects of nerve root retraction during a surgery.
1530-437X/$31.00 © 2013 IEEE
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IEEE SENSORS JOURNAL, VOL. 13, NO. 5, MAY 2013
Fig. 2.
Fig. 3.
Schematic of intraoperative monitoring system.
Prototype of nerve root retractor with embedded pressure sensor.
(a)
The prototype system can potentially alert surgeons about
risk factors associated with nerve root injury during a lumbar
surgery, provide critical surgical guidelines, and serve as a
basis for implementing an intelligent robotically controlled
closed-loop lumbar surgical operating system in the future.
II. I NTRAOPERATIVE M ONITORING S YSTEM D ESIGN
The components of intraoperative monitoring system are
shown in Fig. 2. The MEMS pressure sensor is installed inside
the nerve root retractor, which measures the retraction pressure
and sends the output signal in the millivolts (mV) range to
an interface electronic system. The interface electronic system
further amplifies the signal within a range of 5 V. The signal is
then sent to a digital display unit, which displays the measured
pressure values converted from the voltage signals. Finally,
the data acquisition computer receives the signal by RS-232
interface, which saves and processes the collected data.
Fig. 3 presents an overview of prototype nerve root retractor
design. The retractor structure is made of stainless steel
exhibiting a lateral length of 166 mm and a height of
100 mm, which is typical and convenient for a lumbar surgical
operation.
The tip of the nerve root retractor is designed with an
embedded MEMS pressure sensing module covered by a cambered thin silicone sensing membrane, which can effectively
couple the exerted pressure on a nerve root to a MEMS
pressure sensor underneath [20]. The pressure sensing region
exhibits a height of 2.3 mm, length of 7.5 mm, and width
of 6.7 mm. Fig. 4 presents a detailed schematic view of the
pressure sensing module design with respect to the retractor
structure and a nerve root. The deformation of a nerve root
before and after retraction is also depicted for an illustration
purpose. Exerted force on the nerve root causing structural
deformation is responsible for its neurological injury as will
be discussed in Section IV.
(b)
Fig. 4. Schematic view of intraoperative pressure monitoring module design.
(a) Before retraction. (b) After retraction.
A MEMS piezoresistive pressure sensor is attached over
a thin flexible printed circuit board (PCB) and covered by
a silicone layer for surface protection, forming a pressure
sensing module. Electrical connections are formed by bonded
wires and soldered wires, which can be channeled through
the hallow retractor handle to interface with an external data
acquisition unit. The piezoresistive sensing scheme is chosen
due to its straight forward electronic interface and a nearly
constant operating temperature for the targeted application.
Silicon-silicon-structure-based absolute pressure sensor is used
for retraction pressure measurement. The membrane is fabricated by anisotropic etching. The vacuum chamber is formed
between the membrane and the silicon substrate by silicon-onsilicon bonding technology. The piezoresistors, made by boron
implantation into n-type silicon membrane, placed on the
membrane form a full bridge and provide the voltage output
according to the induced strain from the external pressure.
The sensing module is housed inside the retractor tip
and further encapsulated by a thin silicone membrane as shown
in Fig. 4. The silicone sensing membrane is shaped to exhibit
a cambered surface for achieving an intimate contact with a
nerve root under retraction, thus a more sensitive pressure
coupling for the measurement.
A low retractor tip profile is critical for lumbar surgery
because it determines the minimum displacement of a nerve
root before applying any retraction. In our prototype design,
a 1 mm × 1 mm × 0.6 mm MEMS piezoresistive pressure
sensor is chosen along with a 0.4 mm-thick flexible PCB to
achieve a small tip height of 2.3 mm. Further minimizing the
sensor and PCB thickness will be considered in the future to
reduce the tip height.
A typical nerve root exhibits a diameter around 4 mm.
Surgical retraction can flatten the nerve root as depicted in
LIU et al.: MEMS-BASED INTRAOPERATIVE MONITORING SYSTEM
Fig. 5.
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Schematic of calibration process for the MEMS sensor.
Fig. 7.
Animal experimental research model.
retracted nerve root contacts the silicone sensing membrane is
less than 1 K. In the future, capacitive MEMS pressure sensors
will be considered for the system design due to their zero DC
power dissipation. The obtained performance is adequate for
the proposed intraoperative pressure monitoring application.
III. A NIMAL E XPERIMENTAL M ODEL AND P ROCEDURE
Fig. 6.
Measured sensor cyclic load response.
Fig. 3, resulting in an enlarged nerve root width around
6 mm. Therefore, the pressure sensing region is designed with
a length of 7.5 mm to ensure a reliable contact with the nerve
root. The width of the retractor tip is chosen to be 6.7 mm for
readily installing the pressure sensing module.
A maximum pressure load of 100 kPa was chosen as the
worst-case pressure exerted on a nerve root based on previous
surgical data. The excitation voltage of the MEMS sensor
at the retractor tip is 5 V. This sensor employs a differential Wheatstone bridge architecture and exhibits a nominal
resistance of 5 k. The calibration process for the MEMS
sensor with the components of gas cylinder, digital pressure
calibrator, pressure test fixture and digital multimeter is shown
in Fig. 5. The accuracy of the pressure calibrator is 0.02%.
A special pressure test fixture is used to limit the gas flow
loading to the retractor tip, where MEMS pressure sensor is
located. Three sensor cyclic load processes are conducted for
calibration with gas pressure set by the calibrator equidistantly
among the measurement range and the output voltage signal
measured by the multimeter.
The measured cyclic load response is plotted in Fig. 6,
indicating a repeatability and hysteresis of 0.06% full-scale
(FS) and 0.10% FS, respectively. The device nonlinearity and
sensitivity are as a function of an applied pressure. The worstcase nonlinearity is 0.13% FS and an average sensitivity is
59.74 μV/V/kPa.
The power consumption of the MEMS sensor is
4.73 × 10−3 W. The resulting heat distribution from the
MEMS sensor is insignificant, thus would not cause damage
to the nerve root. The temperature rise at the surface where the
The intraoperative pressure information can be effectively
used to investigate potential neurological injury occurred in a
retracted nerve root. The research results can be used to alert
surgeons about potential risk factors associated with nerve
root injury as well as provide critical surgical guidelines.
Animal experiments were first conducted to characterize the
effectiveness of our prototype monitoring system and obtain
correlation between intraoperative pressure and alteration of
neural tissue structure and related injury. An experimental
research model was established as shown in Fig. 7.
Pressure exerted on a nerve root is monitored by the MEMS
pressure sensing module incorporated in the tip of a nerve root
retractor and is recorded by an external data acquisition unit.
Electrophysiological monitoring and morphological observation are standard medical procedures for characterizing nerve
root injury [21], [22]. Electrophysiological analysis based on
EMG signals is effective for detecting nerve root injury, thus
employed for the prototype development and research. EMG
parameters can be measured after each nerve root retraction,
revealing its functional integrity. A needle electrode is inserted
in an appropriate muscle group innervated by the selected
nerve root. An electrical stimulation is then applied to the
nerve root followed by EMG monitoring. EMG abnormalities
such as a reduction in amplitude and/or an increase in latency
[21], corresponding to a particular surgical manipulation, are
used to correlate with the measured intraoperative pressure.
In addition to the electrophysiological response, morphological observation of the nerve root is also conducted after
retractions. Through optical microscopy, pathological sections
of a nerve root can be inspected. Morphological alteration
of distorted nerve fibers and deformation of nervous tissues
and cells can reflect how neural structure of a nerve root is
damaged, thus confirming injury occurrence.
Intraoperative pressure monitoring experiments were performed under nerve root retractions on laboratory goats
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Fig. 10.
Fig. 8.
Fig. 9.
Pressure and output voltage in a retraction process.
Nerve root retraction experiment conducted in laboratory goat.
Measured electrophysiological response-based EMG signal.
weighting about 20 kg as shown in Fig. 8. A laboratory
goat was placed prone and a midline longitudinal incision
was made, followed by bilaterally retracting the paravertebral
muscle. A lamina was partially resected to explore the lumbar
nerve root.
Two groups of lumbar nerve root were retracted under
different magnitude and duration while the exerted pressure
was monitored by the pressure monitoring module installed
at a retractor tip. A nerve root was retracted for a short
period of time around one minute and then released for a
few minutes to let it recover followed by repeating the same
procedure, thus emulating a real-time surgical environment
and effects. After each retraction, the nerve root was electrically stimulated at three different time intervals to monitor
the corresponding EMG amplitude and latency. The exerted
retraction pressure and cumulative retraction pressure, which is
the sum of the exerted pressure during a retraction period, were
then related to the electrophysiological response to investigate
potential neurological damage.
Neural structural alternations after multiple retraction cycles
were investigated by morphological observation. Pathological
sections of retracted and nonretracted nerve roots were viewed
by optical microscopy for comparison, indicating that effects
of nerve root retraction and associated injury can be revealed
in the nerve root morphological structures, thus serving an
effective procedure to confirm neurological injury.
IV. M EASUREMENT R ESULTS AND D ISCUSSION
A. Effects of Retraction Magnitude on Nerve Root
Two groups of nerve root were retracted under different
amount of pressure to investigate the effect of retraction
magnitude. The pressure sensing module incorporated in the
retractor tip monitored the exerted pressure. The nerve root
electrophysiological test was then conducted at one minute,
three minutes and five minutes after a retraction. The amplitude and latency of the EMG response were recorded. Fig. 9
shows a measured EMG signal after an electrical stimulation
was applied to a nerve root, illustrating the response amplitude
and latency.
The retraction style in animal experiments is the same as
the one in operation, to retract the nerve root by hand for
a short time and then release it. As shown in Fig. 10, the
pressure at the figures following Fig. 10 in this section is the
weighted average value of original pressures in a retraction
process. The weighted average for the retraction process in
Fig. 10 is 15.3 kPa, which is the first pressure data point
presented in Fig. 11(a).
S1 nerve root and adjacent L5 nerve root are usually
involved in lumbar surgery. They exhibit similar properties
for retraction. In the following figures shown in this section,
Group I presents S1 nerve roots of goats and Group II presents
L5 nerve roots of goats.
Fig. 11 presents the measured EMG amplitude versus the
exerted pressure. The amplitude is normalized to a baseline
value, which is the EMG amplitude obtained prior to any
retraction applied to the nerve root. The measurement results
reveal that an increased pressure exerted on a nerve root causes
a reduced EMG amplitude response, indicating an increased
degree of injury to the nerve root.
At each retraction pressure, the measured EMG amplitude
response increases with a prolonged delay time from one
minute to five minutes. This increased amplitude response is
associated with an inherent nerve root recovery process. Note
that the experiments were performed under a limited pressure
range to avoid a permanent injury to the nerve root.
Latency of the electrophysiological response was also measured after each retraction. Fig. 12 presents the measured EMG
latency versus the exerted pressure.
The latency is also normalized to its baseline value. Pressure
exerted on a nerve root causes a prolonged latency, relating
to an increased degree of injury to the nerve root. At each
retraction pressure, it is found that the latency decreases
with a prolonged measurement delay time from one minute
to five minutes. The reduced latency is associated with an
inherent nerve root recovery process. Through the retraction
LIU et al.: MEMS-BASED INTRAOPERATIVE MONITORING SYSTEM
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(a)
(a)
(b)
(b)
Fig. 11. Measured EMG amplitude versus exerted pressure with different
measurement delay times. (a) Group I presents S1 nerve roots of goats.
(b) Group II presents L5 nerve roots of goats.
Fig. 12.
Measured EMG latency versus exerted pressure with different
measurement delay times. (a) Group I presents S1 nerve roots of goats.
(b) Group II presents L5 nerve roots of goats.
experiments, the exerted pressure is correlated with the electrophysiological response, which relates to a neural functional
injury of the nerve root.
Nerve root retraction experiments over an extensive
pressure range or retraction distance were performed to
illustrate a pronounced resulting injury. Fig. 14 shows the
measured intraoperative pressure versus retraction distance for
a selected nerve root.
During the first cycle of retraction, the nerve root was pulled
to 3 mm, 6 mm, and 9 mm with a measured exerted pressure
of 20 kPa, 42 kPa, and 69 kPa, respectively, noting that
69 kPa exerted pressure or 9 mm retraction distance is
considered substantial in lumbar surgery. The nerve root
contains certain structures to resist the effect of retraction.
Neural tissues were extended to absorb the extra energy from
the retraction.
The same retraction procedure was repeated for the second
cycle. The resulting response at retraction distances of 3 mm
and 6 mm was slightly lower than that obtained during the first
cycle due to nerve root viscoelastic behavior [23] and possible
occurred injury. However, a significant reduction in response
was observed at 9 mm retraction distance, which indicates
the second-cycle 9 mm retraction went beyond mechanical
tolerance of the nerve root causing a severe neural tissue
structural breakdown and a permanent neurological damage
[23], [24].
The neural structure alternation due to retraction can be
revealed through morphological observation. After multiple retraction cycles, longitudinal sections of retracted and
nonretracted nerve root were observed by optical microscopy
for comparison as shown in Fig. 15.
B. Effects of Accumulative Pressure on Nerve Root
Besides retraction magnitude, retraction duration can have
a significant impact on a nerve root’s neurological condition.
The cumulative pressure, which is the sum of an exerted
pressure on a nerve root over a retraction duration, was
recorded and investigated for its related nerve root injury.
Fig. 13 presents the measurement data obtained from the two
selected groups of nerve roots under study. Fig. 13(a) shows
the exerted pressure along with the corresponding retraction duration versus measured EMG response amplitude for
Group I nerve root.
The plot consists of four retraction conditions with different exerted pressure and duration. The cumulative pressure
was then determined and plotted against the EMG response
amplitude as shown in Fig. 13(b), where the amplitude
is presented as a normalized quantity with respect to the
corresponding baseline amplitude. Fig. 13(c) shows the EMG
response latency versus the cumulative pressure. It is evident
that a large cumulative pressure causes a more severe injury
to the nerve root, thus a degraded neural function with a
decreased EMG response amplitude and an increased latency.
The measurement data obtained from Group II nerve root are
presented in Fig. 13(d)–(f), revealing a similar behavior.
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IEEE SENSORS JOURNAL, VOL. 13, NO. 5, MAY 2013
(a)
Fig. 14.
Nerve root response under multiple large retractions.
(b)
(c)
(d)
(e)
(f)
Fig. 13. Cumulative retraction effects on nerve root electrophysiological
response. (a) Pressure and retraction duration versus measured amplitude for
S1 nerve root. (b) Cumulative pressure versus measured amplitude for S1
nerve root. (c) Cumulative pressure versus measured latency for S1 nerve
root. (d) Pressure and retraction duration versus measured amplitude for L5
nerve root. (e) Cumulative pressure versus measured amplitude for L5 nerve
root. (f) Cumulative pressure versus measured latency for S1 nerve root.
Irregular arrangement of nerve fibers, accumulation of
inflammatory cells in the vicinity of nerve fibers and necrotic
nervous tissues were clearly observed in the retracted nerve
Fig. 15.
Optical micrographs showing the histology of nerve roots.
(a) Retracted nerve root. (b) Nonretracted nerve root. Hematoxylin-eosin staining of the longitudinal section of the samples. Arrow: Irregular arrangement
of nerve fibers. : Inflammatory cells. NNT: necrotic nervous tissues.
root compared to the nonretracted nerve root. The structural
alternations can impair the nerve conduction and affect its
neurological function.
It is expected that human nerve root injury is related
to the magnitude and duration of retraction in a similar
manner. Therefore, the obtained animal experimental results
and experiences can serves as a starting point for human trials
in the future. The collected clinic data can provide a general
guideline for human lumbar surgery.
V. C ONCLUSION
A MEMS-based intraoperative monitoring system for
improving lumbar surgery safety has been demonstrated.
Animal experiments reveal that a nerve root injury is strongly
related to the magnitude and duration of its retraction. It is
expected that a similar correlation exists for human nerve
roots. The prototype monitoring system can potentially alert
surgeons about risk factors associated with nerve root injury
during a lumbar surgery as well as provide critical surgical
guidelines. It can also serve as a basis for implementing an
intelligent robotically controlled closed-loop lumbar surgical
operating system in the future.
R EFERENCES
[1] M. Sutter, A. Eggspuehler, D. Grob, D. Jeszenszky, A. Benini,
F. Porchet, A. Mueller, and J. Dvorak, “The diagnostic value of
multimodal intraoperative monitoring (MIOM) during spine surgery:
A prospective study of 1,017 patients,” Eur Spine J., vol. 16, no. 2,
pp. 162–170, Nov. 2007.
[2] H. Matsui, H. Kitagawa, Y. Kawaguchi, and H. Tsuji, “Physiologic
changes of nerve root during posterior lumbar discectomy,” Spine,
vol. 20, no. 6, pp. 654–659, Mar. 1995.
LIU et al.: MEMS-BASED INTRAOPERATIVE MONITORING SYSTEM
[3] C. Feltes, K. Fountas, R. Davydov, V. Dimopoulos, and J. S. Robinson,
“Effects of nerve root retraction in lumbar discectomy,” Neurosurg.
Focus, vol. 13, no. 2, pp. 1–2, Aug. 2002.
[4] R. Nagayama, H. Nakamura, Y. Yamano, T. Yamamoto, Y. Minato,
M. Seki, and S. Konishi, “An experimental study of the effects of
nerve root retraction on the posterior ramus,” Spine, vol. 25, no. 4,
pp. 418–424, Feb. 2000.
[5] Y. R. Rampersaud, E. R. P. Moro, M. A. Neary, K. White, S. J. Lewis,
E. M. Massicotte, and M. G. Fehlings, “Intraoperative adverse events and
related postoperative complications in spine surgery: Implications for
enhancing patient safety founded on evidence-based protocols,” Spine,
vol. 31, no. 13, pp. 1503–1510, Jun. 2006.
[6] R. Kraemer, A. Wild, H. Haak, J. Herdmann, R. Krauspe, and
J. Kraemer, “Classification and management of early complications
in open lumbar microdiscectomy,” Eur. Spine J., vol. 12, no. 3,
pp. 239–246, Jun. 2003.
[7] N. R. Malhotra and C. I. Shaffrey, “Intraoperative electrophysiological
monitoring in spine surgery,” Spine, vol. 35, no. 25, pp. 2167–2179,
Dec. 2010.
[8] R. Bošnjak and M. Makovec, “Neurophysiological monitoring of S1
root function during microsurgical posterior discectomy using H-Reflex
and spinal nerve root potentials,” Spine, vol. 35, no. 4, pp. 423–429,
Feb. 2010.
[9] B. Bose, L. R. Wierzbowski, and A. K. Sestokas, “Neurophysiologic
monitoring of spinal nerve root function during instrumented posterior
lumbar spine surgery,” Spine, vol. 27, no. 13, pp. 1444–1450, Jul. 2002.
[10] J. H. Owen, “The application of intraoperative monitoring during surgery
for spinal deformity,” Spine, vol. 24, no. 24, pp. 2649–2662, Dec. 1999.
[11] X. Chen and A. Lal, “Integrated pressure and flow sensor in siliconbased ultrasonic surgical actuator,” in Proc. IEEE Ultrason. Symp., 2001,
pp. 1373–1376.
[12] K. J. Rebello, “Applications of MEMS in surgery,” Proc. IEEE, vol. 92,
no. 1, pp. 43–55, Jan. 2004.
[13] S. Sokhanvar, M. Packirisamy, and J. Dargahi, “MEMS endoscopic
tactile sensor: Toward in-situ and in-vivo and tissue softness characterization,” IEEE Sensors J., vol. 9, no. 12, pp. 1679–1687, Dec. 2009.
[14] P. Peng and R. Rajamani, “Handheld microtactile sensor for elasticity measurement,” IEEE Sensors J., vol. 11, no. 9, pp. 1935–1942,
Sep. 2011.
[15] R. Ahmadi, M. Packirisamy, J. Dargahi, and R. Cecere, “Discretely
loaded beam-type optical fiber tactile sensor for tissue manipulation
and palpation in minimally invasive robotic surgery,” IEEE Sensors J.,
vol. 12, no. 1, pp. 22–32, Jan. 2012.
[16] X. Liu, Q. Huang, M. Qin, H. Chen, and D. Young, “Animal experimental study on the nerve root retraction with a silicon pressure sensor,”
in Proc. IEEE 16th Int. Solid-State Sensors, Actuat. Microsyst. Conf.,
Jun. 2011, pp. 1220–1223.
[17] A. Menciassi, G. Scalari, A. Eisinberg, C. Anticoli, P. Francabandiera,
M. C. Carrozza, and P. Dario, “An instrumented probe for mechanical
characterization of soft tissues,” Biomed. Microdevices, vol. 3, no. 2,
pp. 149–156, Jun. 2001.
[18] A. Pedrocchi, S. Hoen, G. Ferrigno, and A. Pedotti, “Perspectives on
MEMS in bioengineering: A novel capacitive position microsensor,”
IEEE Trans. Biomed. Eng., vol. 47, no. 1, pp. 8–11, Jan. 2000.
[19] J. Rosen, B. Hannaford, M. P. MacFarlane, and M. N. Sinanan, “Force
controlled and teleoperated endoscopic grasper for minimally invasive
surgery-experimental performance evaluation,” IEEE Trans. Biomed.
Eng., vol. 46, no. 10, pp. 1212–1221, Oct. 1999.
[20] P. Cong, W. H. Ko, and D. J. Young, “Wireless batteryless implantable
blood pressure monitoring microsystem for small laboratory animals,”
IEEE Sensors J., vol. 10, no. 2, pp. 243–254, Feb. 2010.
[21] J. Meulstee and F. G. A. van der Meche, “Electrodiagnostic criteria
for polyneuropathy and demyelination: Application in 135 patients with
Guillain-Barré syndrome,” J. Neurol. Neurosurg. Psychiatry, vol. 59,
no. 5, pp. 482–486, Nov. 1995.
[22] R. Jancalek and P. Dubovy, “An experimental animal model of spinal
root compression syndrome: An analysis of morphological changes of
myelinated axons during compression radiculopathy and after decompression,” Exp. Brain Res., vol. 179, no. 1, pp. 111–119, May 2007.
[23] A. Singh, Y. Lu, C. Chen, and J. M. Cavanaugh, “Mechanical properties
of spinal nerve roots subjected to a tension at different strain rates,”
J. Biomech., vol. 39, no. 9, pp. 1669–1676, 2006.
[24] A. Singh, S. Kallakuri, C. Chen, and J. M. Cavanaugh, “Structural
and functional changes in nerve roots due to tension at various strains
and strain rates: An in-vivo study,” J. Neurotrauma, vol. 26, no. 4,
pp. 627–640, Apr. 2009.
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Xing Liu received the B.S. degree from Huazhong
University of Science and Technology, Wuhan,
China, in 2004 and the M.S. degree from Tsinghua
University, Beijing, China, in 2007. She is currently
pursuing the Ph.D. degree at Southeast University,
Nanjing, China.
Her research focuses on biomedical sensor design
and application.
Hui Chen received the B.S.M. degree and the
M.S.M degree from Southeast University, School
of medicine, Nanjing, China, in 1982 and 2004,
respectively.
He joined the Department of Orthopaedics,
Zhongda Hospital, affiliated hospital of Southeast
University, Nanjing, China, as a resident in 1987 and
became an attending doctor in 1993. He has been
the associate chief surgeon from 2003 and ViceChief of the Department of Orthopaedics at Zhongda
Hospital. Moreover, he is Associate Professor of
the Department of Orthopaedics at Southeast University. He specializes in
orthopaedic injuries and complex fracture, including spine injury, pelvis
fractures, femoral neck fractures and supracondylar femur fractures. His
research focuses on the mechanism of orthopedic trauma and novel medical
devices for clinical application.
Dr. Chen is the member of the Specialty Committee of Orthopaedic Trauma,
Chinese Medical Association, Branch of Jiangsu Province. He has also been
the member of the Specialty Committee of Reparative and Reconstructive
Surgery, Chinese Association of Rehabilitation Medicine, Branch of Jiangsu
Province since 2009.
Qing-An Huang (S’89–M’91–SM’95) received the
B.S. degree from Hefei University of Technology,
Hefei, China, in 1983, the M.S. degree from Xidian
University, Xi’an, China, in 1987, and the Ph.D.
degree from Southeast University, Nanjing, China,
in 1991, all in electronic engineering. His Ph.D.
research focused on micromachined GaAs piezoelectric sensors.
After graduation, he joined the faculty of the
Department of Electronic Engineering, Southeast
University, where he became a Full Professor in
1996, and was appointed to Chair Professor for the Chang-Jiang Scholar by
the Ministry of Education in 2004. He is currently the Founding Director of
the Key Laboratory of MEMS of the Ministry of Education, Southeast University. He has authored a book entitled Silicon Micromachining Technology
(Science Press, 1996), and published over 150 peer-reviewed international
journals/conference papers. He is the holder of 30 Chinese patents.
Dr. Huang has currently served as Editor-in-Chief of the Chinese Journal of Sensors and Actuators and Editorial Board member of the Journal of Micromechanics and Microengineering. He was a Conference Cochair for the SPIE-Microfabrication and Micromachining Process Technology
and Devices (Proc.SPIE, vol.4601, 2001), TPC Co-chair of the 7th IEEE
NEMS(Kyoto, 2012) and the 6th Asia-Pacific Conference of Transducers and
Micro/Nano Technologies (Nanjing,2012), TPC Member of TRANSDUCERS’09 &’11&’13 and IEEE Sensors Conference through 2002 to 2012.
Dr. Huang has served as the Founding Chairman of IEEE ED-SSC Nanjing
Chapter. He received the National Outstanding Youth Science Foundation
Award of China in 2003.
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Darrin J. Young (S’93–M’99) received his B.S.,
M.S., and Ph.D. degrees from the Department of
Electrical Engineering and Computer Sciences at
University of California at Berkeley in 1991, 1993,
and 1999, respectively.
Between 1991 and 1993, he worked at HewlettPackard Laboratories in Palo Alto, California, where
he designed a shared memory system for a DSPbased multiprocessor architecture. Between 1997
and 1998, he worked at Rockwell Semiconductor
Systems in Newport Beach, California, where he
designed silicon bipolar RF analog circuits for cellular telephony applications. During this time period he was also at Lawrence Livermore National
Laboratory, working on the design and fabrication of three-dimensional RF
MEMS coil inductors for wireless communications. Dr. Young joined the
Department of Electrical Engineering and Computer Science at Case Western
Reserve University in 1999 as an assistant professor. In 2009 he joined the
Electrical and Computer Engineering Department at the University of Utah
as an USTAR associate professor.
Dr. Young pioneered the research work in MEMS-based, high-Q, tunable
capacitors and on-chip 3-D coil inductors for low-phase noise RF voltagecontrolled oscillator design for wireless communication applications. His
interests include micro-electro-mechanical systems design, fabrication, and
integrated circuits design for wireless sensing, biomedical implant, communication and general industrial applications as well as commercialization of
wireless microsystems. He has published many technical papers in journals
and conferences, and served as a technical program committee member and
session chair for a number of international conferences. Dr. Young was an
associate editor of the IEEE Journal of Solid-State Circuits from 2006 to
2011 and currently serves as the chair of the IEEE Electron Devices Society
MEMS Committee.
IEEE SENSORS JOURNAL, VOL. 13, NO. 5, MAY 2013