784 research outputs found
Floating-disk parylene micro check valve
A novel micro check valve which has nearly ideal fluidic
shunting behaviors is presented. Featuring a parylene-based
floating disk, this surface-micromachined check valve
ultimately realizes both zero forward cracking pressure and
zero reverse leakage in fluidic operations. Two different
floating disk designs have been implemented to demonstrate
functionality of the microvalve. Experimental data of
underwater testing successfully show that in-channel
floating-disk valves in both designs have great fluidic
performance close to an ideal check valve, except the
additional fluidic resistance in the order of 10^(13) N-s/m^5
based on dimensions of the fabricated devices. Their
pressure loading limit have been confirmed to be higher
than 300 kPa without water leakage. This type of micro
check valve is believed to have great use of flow control in
integrated microfluidics and lab-on-a-chip applications
A Micromechanical Parylene Spiral-Tube Sensor and Its Applications of Unpowered Environmental Pressure/Temperature Sensing
A multi-function micromechanical pressure/temperature sensor incorporating a microfabricated parylene
spiral tube is presented. Its visible responses in expression of
in situ rotational tube deformation enable unpowered sensing
directly from optical device observation without electrical or
any powered signal transduction. Sensor characterizations
show promising pressure (14.46°/kPa sensitivity, 0.11 kPa
resolution) and temperature (6.28°/°C sensitivity, 0.24 °C
resolution) responses. Depending on different application
requests, this sensor can be individually utilized to measure
pressure/temperature of systems having one property varying
while the other stabilized, such as intraocular or other in vivo
pressure sensing of certain apparatus inside human bodies or
other biological targets. A straightforward sensor-pair
configuration has also been implemented to retrieve the
decoupled pressure and temperature readouts, hence
ultimately realizes a convenient environmental pressure and
temperature sensing in various systems
Design, fabrication and characterization of monolithic embedded parylene microchannels in silicon substrate
This paper presents a novel channel fabrication technology of bulk-micromachined monolithic embedded polymer channels in silicon substrate. The fabrication process favorably obviates the need for sacrifical materials in surface-micromachined channels and wafer-bonding in conventional bulk-micromachined channels. Single-layer-deposited parylene C (poly-para-xylylene C) is selected as a structural material in the microfabricated channels/columns to conduct life science research. High pressure capacity can be obtained in these channels by the assistance of silicon substrate support to meet the needs of high-pressure loading conditions in microfluidic applications. The fabrication technology is completely compatible with further lithographic CMOS/MEMS processes, which enables the fabricated embedded structures to be totally integrated with on-chip micro/nano-sensors/actuators/structures for miniaturized lab-on-a-chip systems. An exemplary process was described to show the feasibility of combining bulk micromachining and surface micromachining techniques in process integration. Embedded channels in versatile cross-section profile designs have been fabricated and characterized to demonstrate their capabilities for various applications. A quasi-hemi-circular-shaped embedded parylene channel has been fabricated and verified to withstand inner pressure loadings higher than 1000 psi without failure for micro-high performance liquid chromatography (µHPLC) analysis. Fabrication of a high-aspect-ratio (internal channel height/internal channel width, greater than 20) quasi-rectangular-shaped embedded parylene channel has also been presented and characterized. Its implementation in a single-mask spiral parylene column longer than 1.1 m in a 3.3 mm × 3.3 mm square size on a chip has been demonstrated for prospective micro-gas chromatography (µGC) and high-density, high-efficiency separations. This proposed monolithic embedded channel technology can be extensively implemented to fabricate microchannels/columns in high-pressure microfludics and high-performance/high-throughput chip-based micro total analysis systems (µTAS)
Parylene stiction
This paper presents a preliminary study into stiction between parylene C and substrate surfaces for biocompatible check-valve applications. During fabrication, parylene C is used as the structural material for the check-valve. The substrate surfaces studied include Au, Al, Si, parylene C, XeF_2 treated Si, and silicon dioxide. Stiction between different surfaces is created after sacrificial photoresist etching. Then, the stiction is measured using blister tests, and stiction mechanisms for different materials are investigated. The devices are released with different recipes to examine their effects. Finally, the results of the study reveal methods to control the cracking pressure of parylene check-valves
Monolithic High-Aspect-Ratio Embedded Parylene Channel Technology: Fabrication, Integration, and Applications
This paper presents a novel channel fabrication
technology of monolithic bulk-micromachined embedded
channels. Based upon implementing two-step complementary dry
etching technique and conformal parylene C layer deposition,
high-aspect-ratio (internal channel height/internal channel width,
greater than 20) polymer channels with uniform quasirectangular
sidewalls have been successfully fabricated in one silicon wafer. The fabrication is completely compatible with further lithographic CMOS/MEMS process, which enables its total integration with on-chip micro sensors/actuators/structures for lab-on-a-chip applications. An exemplary process has been successfully demonstrated to verify the possibility of combining bulk micromachining and surface micromachining. This proposed formation of channels can be extensively used as beam elements in micromechanical devices or microcolumns for high-performance/high-throughput chip-based separation analysis. A
spiral parylene column longer than 1.1 m embedded in a 3.3 mm
x 3.3 mm chip has been presented as a prospective element in
micro gas-chromatography (µGC)
Floating-disk parylene microvalve for self-regulating biomedical flow controls
A novel self-regulating parylene micro valve is presented in this paper with potential applications for biomedical flow controls. Featuring a free-floating bendable valve disk and two-level valve seat, this surface-micromachined polymeric valve accomplishes miniature pressure/flow rate regulation in a band-pass profile stand-alone without the need of power sources or active actuation. Experimental data of underwater testing results have successfully demonstrated that the microfabricated in-channel valve can regulate water flow at 0-80 mmHg and 0-10 µL/min pressure/flow rate level, which is perfectly suitable for biomedical and lab-on-a-chip applications. For example, such biocompatible microvalve can be incorporated in ocular implants for control of eye fluid drainage to fulfill intraocular pressure (IOP) regulation in glaucoma patients
Wireless Intraocular Pressure Sensing Using Microfabricated Minimally Invasive Flexible-Coiled LC Sensor Implant
This paper presents an implant-based wireless pressure
sensing paradigm for long-range continuous intraocular
pressure (IOP) monitoring of glaucoma patients. An implantable
parylene-based pressure sensor has been developed, featuring an
electrical LC-tank resonant circuit for passive wireless sensing
without power consumption on the implanted site. The sensor
is microfabricated with the use of parylene C (poly-chlorop-
xylylene) to create a flexible coil substrate that can be folded
for smaller physical form factor so as to achieve minimally invasive
implantation, while stretched back without damage for
enhanced inductive sensor–reader coil coupling so as to achieve
strong sensing signal. A data-processed external readout method
has also been developed to support pressure measurements. By
incorporating the LC sensor and the readout method, wireless
pressure sensing with 1-mmHg resolution in longer than 2-cm distance
is successfully demonstrated. Other than extensive on-bench
characterization, device testing through six-month chronic in vivo
and acute ex vivo animal studies has verified the feasibility and
efficacy of the sensor implant in the surgical aspect, including
robust fixation and long-term biocompatibility in the intraocular
environment. With meeting specifications of practical wireless
pressure sensing and further reader development, this sensing
methodology is promising for continuous, convenient, direct, and
faithful IOP monitoring
Microfabricated Implantable Parylene-Based Wireless Passive Intraocular Pressure Sensors
This paper presents an implantable parylene-based wireless pressure sensor for biomedical pressure sensing applications specifically designed for continuous intraocular pressure (IOP) monitoring in glaucoma patients. It has an electrical LC tank resonant circuit formed by an integrated capacitor and an inductor coil to facilitate passive wireless sensing using an external interrogating coil connected to a readout unit. Two surface-micromachined sensor designs incorporating variable capacitor and variable capacitor/inductor resonant circuits have been implemented to realize the pressure-sensitive components. The sensor is monolithically microfabricated by exploiting parylene as a biocompatible structural material in a suitable form factor for minimally invasive intraocular implantation. Pressure responses of the microsensor have been characterized to demonstrate its high pressure sensitivity (> 7000 ppm/mmHg) in both sensor designs, which confirms the feasibility of pressure sensing with smaller than 1 mmHg of resolution for practical biomedical applications. A six-month animal study verifies the in vivo bioefficacy and biostability of the implant in the intraocular environment with no surgical or postoperative complications. Preliminary ex vivo experimental results verify the IOP sensing feasibility of such device. This sensor will ultimately be implanted at the pars plana or on the iris of the eye to fulfill continuous, convenient, direct, and faithful IOP monitoring
Implantable parylene-based wireless intraocular pressure sensor
This paper presents a novel implantable, wireless,
passive pressure sensor for ophthalmic applications. Two
sensor designs incorporating surface-micromachined
variable capacitor and variable capacitor/inductor are
implemented to realize the pressure sensitive components.
The sensor is monolithically microfabricated using parylene
as a biocompatible structural material in a suitable form
factor for increased ease of intraocular implantation.
Pressure responses of the microsensor are characterized
on-chip to demonstrate its high pressure sensitivity (> 7000
ppm/mmHg) with mmHg level resolution. An in vivo animal
study verifies the biostability of the sensor implant in the
intraocular environment after more than 150 days. This
sensor will ultimately be implanted at the pars plana or iris of
the eye to fulfill continuous intraocular pressure (IOP)
monitoring in glaucoma patients
Implantable Unpowered Parylene MEMS Intraocular Pressure Sensor
This paper presents the first implantable, unpowered, parylene-based micro-electro-mechanical-systems (MEMS) pressure sensor for intraocular pressure (IOP) sensing. From in situ mechanical deformation of the compliant structures, this sensor registers pressure variations without power consumption/transduction. Micromachined high-aspect-ratio thin-walled tubes in different geometric layouts are exploited to obtain a high-sensitivity pressure response. An integrated packaging method has been successfully developed to realize suture-less implantation of the device. In vitro testing results have demonstrated that the IOP sensor can achieve 0.67 degree/mmHg angular sensitivity with a spiral-tube design, 3.43 µm/mmHg lateral sensitivity with a long-armed-tube design, and 0.38 µm/mmHg longitudinal sensitivity with a serpentine-tube design. This IOP sensor is designed to be implanted in the anterior chamber of the eye and anchored directly on the iris so that, under incident visible light, the pressure response of the implant can be directly observed from outside the eye, which enables faithful and unpowered IOP monitoring in glaucoma patient
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