JOURNAL OF MICROELECTROMECHANICAL SYSTEMS, VOL. 16, NO. 2, APRIL 2007223

Surface-Micromachined Parylene Dual Valves for
On-Chip Unpowered Microflow Regulation
Po-Jui Chen, Student Member, IEEE, Student Member, ASME, Damien C. Rodger, Student Member, IEEE,
Ellis M. Meng, Member, IEEE, Mark S. Humayun, Member, IEEE, and Yu-Chong Tai, Fellow, IEEE

Abstract—This paper presents the world’s first surface-micromachined parylene dual-valved microfluidic system for on-chip
unpowered microflow regulation. Incorporating a normally closed
and a normally open passive check valve in a back-to-back configuration inside a microchannel, the dual-valved system has successfully regulated the pressure/flow rate of air and liquid without
power consumption or electronic/magnetic/thermal transduction.
By exclusively using parylene C (poly-para-xylylene C) as the
structural material, the fabricated valves have higher flexibility toshunt flows in comparison to other conventional thin-film valves. A
state-of-the-art multilayer polymer surface-micromachining technology is applied here to fabricate parylene microvalves of various
designs. The parylene-based devices are completely biocompatible/implantable and provide an economical paradigm for fluidic
control in integrated lab-on-a-chip systems. Design, fabrication,and characterization of the parylene dual valves are discussed inthis paper. Testing results have successfully demonstrated thatthe microflow regulation of the on-chip dual-valved system canachieve a bandpass profile in which the pressure control range
is 0-50 mmHg with corresponding flow rates up to 2 mL/min for
air flow and 1 L/min flow rate for water flow. This regulation
range is suitable for controlling biological conditions in humanhealth care, with potential applications including drug delivery
and regulation of elevated intraocular pressure (IOP) in glaucoma
patients.
[2006-0126]
Index Terms—Microflow control, microfluidics, microvalve,
parylene.

I. INTRODUCTIONICROELECTROMECHANICAL systems (MEMS)
is an enabling technology to build various microfluidic devices (e.g., channels, valves, pumps, mixers, etc.) forM

Manuscript received June 28, 2006; revised September 1, 2006. This work
was supported in part by the Engineering Research Centers Program of the
National Science Foundation by NSF Award EEC-0310723. Subject Editor Y.
Zobar.
P.-J. Chen and Y.-C. Tai are with the Department of Electrical Engineering,and the Division of Engineering and Applied Science, California Institute ofTechnology, Pasadena, CA 91125 USA (e-mail: pjchen@mems.caltech.edu).
D. C. Rodger is with the Department of Bioengineering, Division of Engineering and Applied Science, California Institute of Technology, Pasadena,
CA 91125 USA. He is also with the Keck School of Medicine, University ofSouthern California, Los Angeles, CA 90033 USA.
E. M. Meng is with the Department of Biomedical Engineering, Viterbi
School of Engineering, University of Southern California, Los Angeles, CA
90089 USA.
M. S. Humayun are with the Keck School of Medicine, University of Southern
California, Los Angeles, CA 90033 USA.
Y.-C. Tai is with the Department of Bioengineering, Division of Engineeringand Applied Science, California Institute of Technology, Pasadena, CA 91125
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/JMEMS.2006.889534

Fig. 1. Typical flow regulation profiles. (a) “Half-pass” regulation, in whichconstant flow rate is controlled with forward pressure loading. (b) “Bandpass”
regulation, in which the flow is conducted only within a pressure loading range.

micro-total-analysis systems ( TAS) and lab-on-a-chip applications [1]–[3]. Microsystems incorporating such miniaturized
devices can be utilized to do chemical/biochemical analysis,
medical treatment, and drug delivery at the microscale. In orderto fulfill systematic and reliable operation of these microfluidic
systems, microflow regulation must be realized to control
sample/buffer fluids. Traditionally off-chip flow regulators areused to maintain the consistency of the fluid source before
introduction to these microsystems, but their size impedes
miniaturization to a complete handheld system or bioimplant.
Therefore, depending on the application, miniaturized flow
regulators with various flow control profiles as shown in
Fig. 1 have been developed and presented [4]–[7]. However,these paradigms are not fully compatible with conventional
micromachining processes, resulting in challenges of integration with other components on a single chip. Accordingly,
a novel microflow regulator consisting of surface-micromachined in-channel microvalves is proposed to achieve on-chip
integration as well as effective flow regulation performance.
Microvalves are the key component to systematically control
microflow for reliable operation [8]. They have the possibilityof being integrated with other microfluidic components stemming from the fact that their mechanical structures are relatively simple. The valves are generally either active or passive,with passive valves (check valves) having the advantages ofsimple operation, zero power consumption, and ease of integration. Because check valves can shunt fluids with a single
pressurized flow direction they are often recognized as “fluidic
diodes.” Fig. 2 shows the shunting behaviors of an electronic
diode and a check valve [9]. Based on their actuation mechanism, micromachined check valves are categorized as normallyopen (Fig. 3(a), fluidic channel is always open unless there issufficient backward pressure) [10] or normally closed (Fig. 3(b),fluidic channel is blocked until pressure is above cracking pressure) [11], [12] valves. However, according to Fig. 2, both typesof check valves are not ideal. For normally open valves the1057-7157/$25.00 © 2007 IEEE

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II. DESIGN

Fig. 2. Fluidic and electronic diodes. (a) Pressure/flow rate curve of a mechanical check valve. (b) I-V curve of an electronic diode.

cracking pressure to conduct forward flow is minimal, while
there is always a leakage problem when backflow is applied. For
normally closed valves, the backflow leakage can be reduced,
but the cracking pressure turns out to be so large that a reasonable flow rate is not achievable with low pressure loading. These
problems are inevitable using current MEMS fabrication technologies.
Even though micromachined check valves are not ideal, different design schemes can be implemented to realize different
fluidic behaviors from those in a single valve. In this paper, anovel dual-valve configuration has been developed to achieve
passive microflow regulation as shown in Fig. 1(b) by incorporating a normally closed check valve and a normally open
check valve together inside a microchannel. This configuration
inherently regulates pressure and flow rate of fluids without any
power consumption and greatly reduces the complexity of device fabrication and integration compared with other existing
micro flow regulators. In addition to implementing similar design concepts from previous work [10], [11], both the design
and fabrication of normally closed and normally open checkvalves have been modified and improved so that the in-channel
dual-valved system is capable of controlling flows in a miniature
regulation range [13]. This specific regulation range in a “bandpass” profile further favors biological conditioning in humanhealth care. For example, a dual-valved device can be implanted
in a glaucoma patient’s eye to facilitate physical regulation of
his or her elevated IOP. By shunting eye fluid in a specified pressure band, the implant protects the eye from hypotony by stopping drainage when the IOP is lower than the predeterminedthreshold point. It also prevents excessive eye fluid drainage
during acute IOP spikes not due to glaucoma, such as whenthe eye is rubbed, pressed, hit. As used in drug delivery a dualvalved device can more accurately deliver a dose and prevent
overdelivery of medication when the fluidic pressure is higher
than the regular range [4]. Such a configuration can also be fully
integrated in lab-on-a-chip systems for refined flow regulationin life science analysis and research.

In order to accomplish the target flow regulation profile asshown in Fig. 1(b), the back-to-back dual-valved configuration
illustrated in Fig. 3(c) has been developed. This configuration
requires only two in-channel check valves. By placing a normally closed valve in forward flow operation at the inlet andplacing a normally open valve in backward flow operation at
the outlet of a microchannel, the overall fluidic behavior of thedual-valved system combines the dashed regions of Fig. 3(a)and Fig. 3(b), resulting in the pressure/flow rate curve shownin Fig. 3(c). In this configuration, the normally closed checkvalve dominates the fluidic control in terms of conducting flows
through the channel at pressures higher than the threshold point.
The normally open check valve works in reverse leakage mode
hence serving as a fluid stopper, in which flow is conducted at
low pressures but blocked with applied pressures higher thanthe cut-off point. If the individual check valves are well-tuned,this passive in-channel dual-valved microsystem is able to spontaneously regulate pressure/flow rate in the designated rangeof forward flows in a “bandpass” profile without active actuation or power consumption. Additionally, this configuration isleak-proof to backward flows due to the characteristics of thenormally closed valve at channel inlet. Because the dual valvesmust be integrated in-channel for this back-to-back operation,
they were designed to be surface-micromachined for fabrication
convenience.
Fig. 4 shows the designs of these microcheck valves. They are
essentially thin-film structures microfabricated on a substrate.
A free-standing membrane suspended by tethers acts as the normally open check valve, in which fluids can easily flow throughin the forward direction while reserve leakage occurs in backflow [10]. This is because the membrane is suspended on top of
the port orifice so that the flow is not blocked until backward
pressure loading is applied to snap the membrane to the valve
seat. The normally closed valve, on the other hand, needs a prestressing force to block the port orifice so forward flow can notpass through without sufficient pressure loading. Therefore, avacuum-collapsed sealing method [11] was implemented to realize this valve behavior. Here, a valve membrane is connected
to a surrounding ring chamber. When there is a sufficient pressure difference applied between the inside and outside of thechamber, the chamber top wall can be collapsed, resulting in
the connected membrane being dragged downward and furtherpressed against the valve seat as long as the space between thevalve and the valve seat is smaller than the chamber height. At
this time flows can not be conducted unless the valve membrane
is popped up with forward pressure loading, which realizes the
dynamic behavior of a normally closed check valve. With sophisticated mechanical design, the check valves can be operated
in harmony to achieve the desired microflow regulation capability. Because the crucial part of dual-valve operation is to ensure that the cracking pressure of the normally closed valve iswell controlled, its mechanical design was verified by iterative
FEMLAB (now called COMSOL Multiphysics) simulations toestimate the valve performance based on finite element method(FEM) [14]. As shown in Fig. 5, the ring chamber was first simulated to find the collapse point of valves of different dimensions

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225

Fig. 3. Concept of dual-valved microflow regulation. Combining the single valve behavior shown in the dashed regions of (a) and (b) in a “back-to-back” configuration results in the passive “bandpass” pressure/flow rate regulation shown in (c). Block arrows in valve schematics denote the forward flow direction.

Fig. 4. Cross section of normally closed (left) and normally open (right) microcheck valves. Arrows in normally closed valve denote the dragging direction
when the chamber is collapsed by vacuum sealing, causing the connected valve
membrane to be prestressed to the valve seat.

with a constant pressure difference (ambient pressure outside
the chamber and vacuum inside the chamber). After the prestressing force with respect to height difference was obtained
due to chamber collapse, it was used as a condition to simulate the required pressure loading to pop up the connected membrane. If the desired result was not attained then the dimensionsof the valve structure (the chamber and the membrane) werechanged and the simulation repeated. By such iterative simulation the behavior of the normally closed valve could be well estimated. Depending on dimensions and the use of straight-armedor twisted-armed tethers to suspend the membrane, single checkvalves can have different structural rigidities and their fluidic behaviors (flow resistance, cracking pressure, etc.) are correspondingly altered. As a result, microflow regulation with varying
pressure/flow rate ranges can be virtually determined. Here thecracking pressure of the normally closed check valve was designed to be 10 mmHg to realize the threshold point in the bandpass flow regulation profile.
Because the dual-valved system is proposed to achieve
miniature pressure/flow rate regulation in life science applications, parylene C (poly-para-xylylene C) was selected as the
structural material due to its mechanical flexibility (Young’s

Fig. 5. FEMLAB simulations to estimate prestressing force of thevacuum-collapsed chamber (top) and resultant threshold pressure applied
to valve membrane (bottom) to shunt fluids. By coupling these simulations the
dynamic behavior of a complete normally closed check valve was determined.
The resultant out-of-plane device deflections in the figures were obtained byusing the dimensions shown in Table I under 10 mmHg popping-up pressureloading.

modulusGPa), chemical inertness, biocompatibility (USP
Class VI grade), and CMOS/MEMS process compatibility [15],[16]. Furthermore, conformal parylene deposition takes place
mtorr), which facilitatesat room temperature in a vacuum (the vacuum-collapsed sealing of the normally closed checkvalve. Because parylene is much more flexible than poly-silicon and other conventional materials, the parylene-based
microcheck valves ideally have higher compliance and better
fluidic shunting performance compared to other thin-film

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Fig. 6. Fabrication process flow.

TABLE IDESIGN METRICS OF THE IN-CHANNEL DUAL VALVES IN THIS PAPER

Fig. 7. Three-level sacrificial photoresist layer coating using three-step partial
exposure lithography. (a) Cross-section schematic and top-view micrographs of
the fabricated structures. (b) 3-D profile scan of (a).

considered in these simulations. Final design metrics of thein-channel dual valves are summarized in Table I.
III. FABRICATION

valves [17], thus, accomplishing microflow regulations withhigh resolution. In addition, the devices comprise completely
biocompatible/implantable materials so it is feasible to usethem in biochemical/chemical analysis and human bioimplants.
To enable more accurate design and estimation of the dual
valves, the thin-film residual stress of parylene C [18] was also

The fabrication process illustrated in Fig. 6 started withgrowing a 2– m wet oxide on a standard 4 silicon wafer. The
backside oxide was then patterned as a mask with bufferedhydrofluoric acid (BHF) and the backside exposed silicon
was bulk-etched with potassium hydroxide (KOH) solution,leaving approximately 25– m membranes to define fluidic
coupling ports. Ultimately these ports were used to provide
fluidic access at the inlet and outlet of the microchannel. Afterremoving the frontside oxide, the wafer was placed in air forsome time to grow native oxide so that 0.5% saline A-174(Specialty Coating System Inc., Indianapolis, IN) solution (DICHEN et al.: SURFACE-MICROMACHINED PARYLENE DUAL VALVES

227

Fig. 8. Micrographs of the fabricated dual-valved channel (2 mm long in port-to-port distance) and cut-in views of the normally closed (left) and normally open
(right) parylene check valves (top view). The diaphragm tethers can be designed as straight arms or twisted arms depending on performance requirements.

water:IPA:A-174 = 100:100:1 in volume) could be properly
applied to promote adhesion between parylene C layer and thesubstrate. A multilayer surface-micromachining technology
was subsequently utilized to build in-channel valve structuresconsisting of photoresist as sacrificial layers and parylene C as
structural layers. AZ4620 (Clariant Corp., Charlotte, NC) was
selected as the spin-coated photoresist material and parylene C
deposition was conducted in a Cookson Electronics PDS 2010
system (Specialty Coating Systems Inc.). Details regarding dimensions of device features are noted in Table I. The sacrificial
photoresist layers were hard-baked at 120 C after lithography
if applicable for edge-smoothening and degassing purposes. All
parylene C layers were slightly roughened by a short period of
oxygen plasma treatment in order to both reduce stiction [11]and promote adhesion in between each structural layer [19] inthe fabricated devices. Cleaning procedures were also carefully
taken on wafers before every parylene coating for stronger
interlayer adhesion. Parylene layers were patterned by using an
oxygen plasma etch with AZ4620 as the mask material to define
device features. With these parylene processes, fabrication of
the valve seats, check valves, and integrated microchannels was
performed. After etching away the backside silicon membraneby either deep-reactive-ion etching (DRIE) or gas-phaseetching to open through holes and stripping photoresist withacetone, an additional frontside parylene C coating was finallyconducted to accomplish the vacuum-collapsed sealing for thenormally closed valve. Overall, the developed micromachining
process includes five layers (four structural layers and one
vacuum sealing layer) of parylene to completely fabricate thepolymer-based dual-valved microfluidic system.
During processing the normally closed valve was the mostcomplicated component because the height of the ring chamber
and the spacing between valve membrane and valve seat have tobe appropriately defined to realize vacuum-collapsed sealing.
Consequently, as shown in Fig. 7, a three-step partial-exposure
lithography was applied to a single sacrificial photoresist layer
in order to construct a three-level base featuring a vacuum-collapsed ring chamber, a valve-seat contact, and a etching/sealing

channel of a normally closed valve. In these structures, a
7- m-high chamber was connected to a 2- m-high channel
for both final photoresist stripping and 1.5- m-thick parylene
vacuum sealing through that channel. A 5- m-thick photoresist
spacer between the valve and the valve seat was also defined at
the same time to control the prestressing force and thresholdpressure loading of the fabricated valve by its height difference
to the ring chamber. The 3-D profile scan taken with a P-15
surface profilometer (KLA Tencor Corp., San Jose, CA), as
shown in Fig. 7(b), confirms that the three-level structures were
fabricated as expected. Good planarization by spin-coating
thick photoresist over the three-level structures was thenrequired to create a flat valve membrane corresponding touniform device performance. As for the normally open checkvalve, because it is designed to operate under reverse flow, acover with a central orifice was placed on top of the valve toensure the valve membrane encounters flows from above. Thus
pressure loading can be properly applied as expected, which
enhances the predictability of the reverse leakage behavior of
the normally open valve. Fig. 8 shows the fabricated in-channel
parylene dual valves. Channels with both single valves and dual
valves were fabricated on-chip to experimentally characterize
their behavior.
IV. EXPERIMENTAL SETUP
Microfabricated in-channel parylene single check valves anddual valves were tested using the fluidic setup illustrated inFig. 9. A customized testing jig featuring polyetheretherketones(PEEK) material was used to provide a macroscale/microscale
fluidic interface with diced chips so that microflows could
be introduced with regular tubing and fittings to the devices
through their backside fluidic access ports [20], [21]. Both
compressed air and water served as the fluid source for device
characterization. On the front end of the jig, an off-chip pressure
regulator and a pressure gauge were connected to control the
injection pressure of the fluids. Although hydrostatic pressure
generated by the gravitational effect of liquid column was not
employed, the tuning resolution of the applied gauge pressure

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Fig. 9. Schematic of fluidic connection setup for device testing.

in this setup was up to 0.01 psi (mmHg), which is sufficient for the desired regulation regime. Flow rate measurement
and fluid collection was performed on the back end of thejig. Based on different viscosities of sample fluids, flow ratemeasurement was accomplished via different methods. Air flowrate was measured with an off-chip flow meter due to its large
value (mL/min range), while water flow rate was measured
by recording the marching velocity of the water column front
in the capillary due to its relatively small flow rates ( L/min
range). In marching velocity measurements, given the fact thatthe recording resolution was limited to 0.5 mm in marching
distance and 1 s in marching time in this setup, the overall flowrate measurement error was approximately 5%–15% dependingon the flow rate. Using these measurement techniques with theabove considerations, the pressure/flow rate behavior of thedevices for different fluids could be correctly characterized.
V. RESULTS AND DISCUSSION
Pressure/flow rate testing results of the micromachined
in-channel valves are shown in Figs. 10 and 11 using air andwater as the working fluids. Pressure readouts are presented
in gauge pressure format to indicate the additional pressureloading from the injected fluids relative to atmospheric pressure.
Incompressible flow was assumed for air flow measurements.
These data show that air flow rate was much higher than waterflow rate as expected due to their viscosity difference. The
tested valves were all of the twisted-arm tether type in order toobtain more compliant deflection (mechanical response) withpressure loading compared to the straight-arm tether type [10].
In the following two sections, characterization results of thein-channel single valve and dual valve operation are described.
A. Single Valve Testing
Under single-valve operation, the fabricated normally closed
check valve demonstrated a remarkably low cracking pressureof approximately 0.2 psi ( 10 mmHg) for both air and waterflow as shown in Figs. 10(a) and 11(a). This is a result of thefluidic pressure being applied on the central area of the flexible membrane, thus, effectively overcoming the prestressing
force of the vacuum-collapsed chamber and shunting the fluids
to the microchannel. Lower cracking pressure was obtained with
air than with water as the fluid, implying that air is generally
easier to shunt than water because a higher interfacial disturbance (e.g., capillary effect) appeared at the hydrophobic parylene C surface. As a result, additional pressure loading is required for water to flow in parylene channels. In backward operation, there was no reverse leakage occurring in the normallyFig. 10. Single valve operation with air as the working fluid. (a) Pressure/flowrate curve of the normally closed check valve. (b) Pressure/flow rate curve of
the normally open check valve.

closed valve with pressure loading greater than 25 psi, close to
the maximum limit of the off-chip regulator and pressure gauge
in the testing setup. For the normally open check valve, as shownin Figs. 10(b) and 11(b), no obvious cracking pressure effect wasobserved and a higher flow rate was obtained with the same degree of pressure loading. Given the fact that the valve membrane
designs in the normally open valve and the normally closed
valve were different, the forward flow resistance of the normally

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229

TABLE IICOMPARISON OF REPORTED PARYLENE MICROCHECK VALVES (WITH WATER AS THE WORKING FLUID)

This leak rate started to decrease when the pressure loading wasmmHg) and was greatly suppressedhigher than 0.6 psi (with pressure loading higher than 1 psi (mmHg), which
implies that the valve membrane was in firm contact with valve
seat. The breakdown pressure was confirmed at more than 25 psiwith no obvious leak rate within this range of pressure operation. Even though a wide variety of designs of different dimensions were implemented, some figures of merit of the single
in-channel parylene valves were compared with reported parylene microcheck valves [10]–[12] in Table II to briefly describe
the improvement of the valves in this paper.
B. Dual Valve TestingFig. 11. Single valve operation with water as the working fluid. (a) Pressure/flow rate curve of the normally closed check valve. (b) Pressure/flow rate
curve of the normally open check valve.

open valve was significantly lower compared to that of the normally closed valve. In terms of reverse leakage, the backward
mmHg) with a peakflow rate was obtained within 1.5 psi (at more than 2 mL/min for air flow and 2 L/min for water flow.

Miniature pressure/flow rate regulation was successfully performed in dual valve operation. Fig. 12 shows that, by combining the behaviors of the single check valves, the dual-valved
microsystem was able to regulate pressure in the range of 0–1 psi( – mmHg) with measured flow rates of up to 0.7 mL/min
for air flow and 1.3 L/min for water flow. Because more microfluidic elements were placed in dual valve configuration thanin single valve configuration, a large fluidic resistance obtainedby the dual check valves with a microchannel results in relatively small flow rates. As expected, no reverse leakage was observed with pressure loading greater than 25 psi.
The micromachined in-channel parylene valves were successfully characterized with reliable and repeatable behaviors
from the same device in cyclic operation regardless of errors ingauge pressure and marching velocity/flow rate measurements.
However, their performance unavoidably had some extent
of variation. For example, the measured cracking pressureof the normally closed check valves from the same batch of
fabrication varied from 8 to 13 mmHg based on the tested
devices in this paper, while still being in good agreement withthe designed value of the popping-up pressure loading from the
FEMLAB simulations. The following three factors related to
the fabrication process contributed to the resultant variation:1) thickness control of photoresist coating; 2) thickness controlof parylene C deposition; and 3) material property control ofthin-film parylene C. Consequently, more process calibrationand characterization should be conducted in order to enhance
uniformity of the device performance so that the bandpass pressure regulation range can be precisely controlled depending on
specific application.

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can be utilized for many applications in lab-on-a-chip systems
for life science research, such as drug delivery and regulation of
the elevated IOP of glaucoma patients.

ACKNOWLEDGMENT
The authors especially thank T. Roper for his fabrication
assistance.

REFERENCES

Fig. 12. Dual valve operation for miniature microflow regulation. (a) Air flow
regulation. (b) Water flow regulation.

VI. CONCLUSION
A parylene-based unpowered dual-valved microflow regulation system has been successfully developed. By incorporatinga normally closed and a normally open check valve in back-toback configuration inside a microchannel, fluid pressure/flowrate can be systematically controlled. Because of the passive
operation of the check valves, only mechanical elements wereinvolved and no power consumption/transduction was required.
A multilayer surface-micromachining technology was applied
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CHEN et al.: SURFACE-MICROMACHINED PARYLENE DUAL VALVES

Po-Jui Chen (S’03) was born in Taipei, Taiwan, in
1980. He received the B.S. degree in mechanicalengineering from the National Taiwan University,
Taipei, Taiwan, in 2002, and the M.S. degree inelectrical engineering from the California Instituteof Technology (Caltech), Pasadena, in 2004, andcurrently, he is working towards the Ph.D. degree
in electrical engineering in the area of MEMS at theCaltech Micromachining Laboratory.
He joined Dr. Y.-C. Tai’s Caltech Micromachining
Laboratory as a Graduate Researcher in 2003. He has
authorized more than ten peer-reviewed journal and conference papers. His research interests include implantable biomedical microdevices, integrated microfluidic systems, micro-total-analysis systems (TAS), MEMS sensors/actuators/structures, and micro/nanofabrications.
Mr. Chen received several scholarships, the Sorenson Fellowship, the outstanding college youth award at National Taiwan University in 2002, and waselected as an honorary member of the Phi Tau Phi scholastic honor society in
Taiwan in 2002. He is the recipient of the Student Poster Award in the International TAS 2006 Conference in Tokyo, Japan. He is a student member of theAmerican Society Of Mechanical Engineers (ASME) and the Association for
Research in Vision and Ophthalmology (ARVO) and a full member of Sigma
Xi—the scientific research society.

Damien C. Rodger (S’97) received the B.S. degree
in electrical engineering (magna cum laude withhonors) from Cornell University, Ithaca, NY, in 2000.
Currently, he is working towards the M.D./Ph.D.
degree at the Keck School of Medicine, the University of Southern California, Los Angeles, and theCalifornia Institute of Technology, Pasadena, conducting research in bioengineering under Dr. Y.-C.
Tai and Dr. M. Humayun in the area of bioMEMS
for ophthalmic use.
His MEMS research while at Cornell University
concentrated on SCREAM-fabricated microwave transmission lines and continuous phase shifters, conducted under Dr. N. MacDonald, and on biomotordriven microdevices as a W.M. Keck Foundation Fellow in nanobiotechnology
under Dr. C. Montemagno. He also worked in the MEMS group at the NASA Jet
Propulsion Laboratory on the Coriolis force vibratory microgyroscope, under
Dr. T. Tang and Dr. W. Tang.
Mr. Rodger held a Whitaker Foundation Graduate Fellowship in Biomedical
Engineering from 2003 to 2006. He a student member of the Association for
Research in Vision and Ophthalmology (ARVO).

Ellis M. Meng (M’02) received the B.S. degree in engineering and applied science and the M.S. and Ph.D.
degrees in electrical engineering from the California
Institute of Technology (Caltech), Pasadena, in 1997,
1998, and 2003, respectively.
She joined the Biomedical Engineering Department at the University of Southern California, Los
Angeles, in summer 2004. Her research interests
include bioMEMS, implantable biomedical microdevices, microfluidics, multimodality integrated
microsystems, and packaging. Currently, she is a

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Researcher in the National Science Foundation Biomimetic MicroElectronic
Systems Engineering Research Center (BMES ERC) in which she is a Thrust
Leader for Interface Technology and the Associate Director of Education andStudent Diversity.
Dr. Meng was a recipient of the Intel Women in Science and Engineering
Scholarship, Caltech Alumni Association Donald S. Clark Award, and Caltech
Special Institute Fellowship. She is a recipient of the NSF CAREER award
and a member of Tau Beta Pi, the American Society Of Mechanical Engineers(ASME), the Society of Women Engineers (SWE), and the Association for Research in Vision and Ophthalmology (ARVO).

Mark S. Humayun (M’97) received the B.S. degreefrom Georgetown University, Washington, DC,
in 1984, the M.D. degree from Duke University,
Durham, NC, in 1989, and the Ph.D. degree from the
University of North Carolina, Chapel Hill, in 1994.
He finished his training by completing an Ophthalmology Residency at Duke University and a
Fellowship in Vitreoretinal diseases at The Johns
Hopkins Hospital. He stayed on as faculty at The
Johns Hopkins Hospital while he became the Associate Professor. Currently, he is a Professor of
Ophthalmology, Biomedical Engineering, and Cell and Neurobiology at the
University of Southern California, Los Angeles. He is the Director of the National Science Foundation Biomimetic MicroElectronic Systems Engineering
Research Center (BMES ERC). He is the Co-Developer of a retinal implantthat has received wide attention for its potential to restore sight. He is also
the Director for the Department of Energy Artificial Retina Project that is a
consortium of five Department of Energy labs and four universities, as wellas industry. His research interests include retinal prostheses, implantablemicroelectronics, and ophthalmic surgical instrumentation.
Dr. Humayun is a member of the Biomedical Engineering Society, the Association for Research in Vision and Ophthalmology (ARVO), the Vitreous Society,and the Retina Society.

Yu-Chong Tai (M’97–SM’03–F’06) received the
B.S. degree in electrical engineering from the
National Taiwan University, Taipei, Taiwan, in
1981 and the M.S. and Ph.D. degrees in electricalengineering from the University of California at
Berkeley in 1986 and 1989, respectively.
He joined the Faculty of Electrical Engineering
at the California Institute of Technology (Caltech),
Pasadena, where he built the Caltech Micromachining Laboratory and currently is a Professor of
Electrical Engineering, Mechanical Engineering,and Bioengineering. Hi current research interests include flexible MEMS,
bioMEMS, MEMS for retinal implants, parylene-based integrated microfluidics, neuroprobes/neurochips, and HPLC-based lab-on-a-chip systems.
Dr. Tai received several awards such as the IBM fellowship, the Best ThesisAward, the Presidential Young Investigator (PYI) Award and the David and Lucile Packard Fellowship. He Co-Chaired the IEEE International MEMS 2002
Conference, Las Vegas, NV.