Teimour Maleki - Academia.edu (original) (raw)

Papers by Teimour Maleki

In this work two novel valve devices are proposed for treatment of glaucoma. By opening or closin... more In this work two novel valve devices are proposed for treatment of glaucoma. By opening or closing, the proposed valves can be used to reduce high pressures in the eye (hypertony), or prevent low pressures in the eye (hypotony) respectively. These devices work based on the buckling of fluid channel connected to the anterior chamber of the eye. The first proposed valve is fully mechanical while the second proposed device is magnetically driven

ABSTRACT Batch compatible laser micromachining of an elastomeric cantilever actuator composed of ... more ABSTRACT Batch compatible laser micromachining of an elastomeric cantilever actuator composed of a polydimethylsiloxane (PDMS) bilayer (active/inactive) and soft-lithographically patterned conductive carbon grease electrodes is presented in this paper. Low actuation voltage and large out-of-plane displacement are unique characteristics of this new cantilever structure. An actuator which is 4mm long, 1mm wide, and 80μm thick can produce up to 1.2mm out of plane displacement and generate maximum force of 25μN when actuated by 450V.

In this paper we present the low cost, batch compatible fabrication of a single-touch catalytical... more In this paper we present the low cost, batch compatible fabrication of a single-touch catalytically-activated electrochemical micropump, using hydrogen peroxide for the first time. After first mechanically initiation (e.g., a single finger touch), this micropump is capable of achieving high volume rate 67μl/min and high backpressure without the requirement for an electrical power source. These features make the micropump an ideal candidate for low-cost and compact microfluidic products.

In this paper, we present the development of two radiation detectors for accurate dose monitoring... more In this paper, we present the development of two radiation detectors for accurate dose monitoring in radiation oncology. The first one is a passive MEMS-based miniature ionization chamber for total accumulated dose measurement. A sensitivity of 49 kHz/Gy in a dynamic range of 30 Gy was achieved in an LC configuration. The second transducer is based on a sensitive solid-state structure that can be used in active interrogation schemes. This sensor exhibited a sensitivity of 50 kÂ¿/Gy in a dynamic range of 20 Gy.

IEEE/ASME Journal of Microelectromechanical Systems, 2008

ABSTRACT Although 3-D out-of-plane structures based on the thermal shrinkage of polyimide-filled ... more ABSTRACT Although 3-D out-of-plane structures based on the thermal shrinkage of polyimide-filled V-grooves have already been demonstrated, for large bending angles, this method typically requires several V-grooves and high curing temperatures, which are real-estate consuming and can damage temperature-sensitive components. In this paper, we show that the addition of an inorganic layer (called the boosting layer) beneath the V-grooves can significantly enlarge the bending angle without requiring more V-grooves or higher curing temperatures. For example, a 2- -thick boosting layer can raise the bending angle of a single V-groove joint by a factor of seven. In addition, the boosting layer removes the requirement for a V-groove and permits the use of straight-wall dry-etched grooves, hence allowing a sharper curvature in a smaller area.

Journal of Micromechanics and Microengineering, 2010

ABSTRACT Recording a neural ensemble has been an extremely successful experimental paradigm allow... more ABSTRACT Recording a neural ensemble has been an extremely successful experimental paradigm allowing real-time interpretation of neural codes as well as the detection of dynamic changes within a process. In recent years, microfabricated electrodes have attracted a great deal of attention for recording neural ensembles with superior resolution and spatial density. A 3D microfabricated electrode is particularly attractive since it yields enhanced performance with regard to spike sorting and single unit detection. In this paper, we describe a self-assembly process for fabricating 3D microelectrode arrays in silicon. The electrode array is composed of four silicon shanks (200 µm wide, 4 mm long and 30 µm thick) with polyimide-filled V-groove joints at the back end and four 20 × 20 µm2 recording sites (200 µm separation) at the tip. The shanks automatically fold to a vertical configuration upon proper heat treatment, hence creating a 3D configuration without the need for any manual assembly. Impedance and electrical test-signal measurements were used to verify the electrode functionality after the folding process.

This paper presents a novel minimally invasive implantable pressure sensing transponder for conti... more This paper presents a novel minimally invasive implantable pressure sensing transponder for continuous wireless monitoring of intraocular pressure (IOP). The transponder was designed to make the implantation and retrieval surgery simple while still measuring the true IOP through direct hydraulic contact with the intra-ocular space. Most parts of the sensor sit externally on the sclera and only a micro-needle penetrates inside the vitreous space through pars plana. In vitro tests showed a sensitivity of 15 kHz/mmHg with about 1 mmHg resolution. In vivo tests included one month implantation in rabbits, confirming the device biocompatibility and functionality.

IEEE Transactions on Biomedical Circuits and Systems, 2010

Intensity-modulated radiation therapy (IMRT) requires precise delivery of the prescribed dose of ... more Intensity-modulated radiation therapy (IMRT) requires precise delivery of the prescribed dose of radiation to the target and surrounding tissue. Irradiation of moving body anatomy is possible only if stable, accurate, and reliable information about the moving body structures are provided in real time. This paper presents a magnetic position tracking system for radiation therapy. The proposed system uses only four transmitting coils and an implantable transponder. The four transmitting coils generate a magnetic field which is sensed and measured by a biaxial magnetoresistive sensor in the transponder in the tumor. The transponder transmits the information back to a computer to determine the position of the transponder allowing it to track the tumor in real time. The transmission of the information from the transponder to the computer can be wired or wireless. Measurements using a biaxial sensor agree well with the field strength calculated from the ideal equations. The translation from the measurement data to the 3-D location and orientation requires a numerical technique because the equations are in nonclosed forms. The algorithm of tracking is implemented using MATLAB. Each calculation of the position along the target trajectory takes 30 ms, which makes the proposed system suitable for real-time tracking of the transponder for radiation assessment and delivery. An error of less than 2 mm is achieved in the demonstration.

Sensors and Actuators A-physical, 2004

An ultraviolet assisted chemical etching of plastic is reported in which the etching of PET subst... more An ultraviolet assisted chemical etching of plastic is reported in which the etching of PET substrates is anisotropic in the direction of light illumination. A strong solvent as di-methyl-formamide (DMF) is exploited to perform the chemical etching process and patterning of the desired structures is feasible using a Ge/Cu bi-layer as the masking film. Etch rate depends strongly on the intensity of the ultra-violet light and temperature of the solution during this etching process. An average etch rate of 15 m/h is achieved with little mask undercut in the presence of 6-8 mW/cm 2 of 365 nm UV at a temperature of 120 • C. The highest achieved etch rate in this technique is 40 m/h using an intensity of 16 mW/cm 2 for the UV illumination. The effects of solution temperature during etching, the intensity of light, and the amount of the solvent above the sample have been studied. This technique has been applied to etch 80 m of PET substrates and to make 40 m thick square membranes with an area of 500 m × 500 m. Also 120 m thick micro-gears have been realized with a diameter of 900 m. The gears have been freed and installed on their corresponding axels with a diameter of 100 m.

As the position of the tumor in a patient moves during radiation therapy, real-time knowledge of ... more As the position of the tumor in a patient moves during radiation therapy, real-time knowledge of the position of the tumor is necessary in order to allow the maximum amount of radiation to be focused on the tumor and the minimum damage on the surrounding healthy tissues. A 0.5-V sub-mW wireless active transponder for a magnetic tracking system is designed in 130-nm CMOS technology to track the position of the tumor. The transponder consumes only 912 μW and an error of less than 5 mm is achieved with the tracking system.

In this paper, we present several implantable micro-devices targeted towards improving the effica... more In this paper, we present several implantable micro-devices targeted towards improving the efficacy of radiation therapy. Three micro-devices are discussed: a self-biased solid state dosimeter to be used for wireless monitoring of the delivered dose, an electromagnetic tracking system to locate the position of tumor in real-time, and a Guyton-chamber-embedded capacitive pressure sensor for wireless measurement of interstitial pressure inside a tumor. Dosimeter and tracking systems are developed to be integrated together to achieve a track-able radiation sensor. Guyton chamber of the pressure sensor will eliminate the sensor drift due to the interaction of cells and fibrous tissue with sensor's membrane. The dosimeter has a sensitivity of up to 9 kΩ/Gy and a dynamic range of 10 Gy, when operating with a zero bias voltage. The tracking system is able to track a tumor that is 60 cm away with a resolution of 2 mm and a dynamic range of up to 5 cm. Finally, the capacitive pressure sensor has a sensitivity of 75 fF/kPa and a dynamic range of 60 mmHg.

This paper presents design, fabrication, and implementation of a novel electromechanical energy s... more This paper presents design, fabrication, and implementation of a novel electromechanical energy scavenging and wireless interrogation scheme using low frequency components of musical vibrations to overcome challenges associated with previously reported passive transponders such as: short transmission range, misalignment sensitivity, and complicated receiver circuitry. The transponder has two phases of operation: 1) mechanical vibration phase, in which an acoustic receiver (a piezoelectric cantilever) converts the sound vibration into electrical power and charges a capacitor; and 2) electrical radiation phase, in which the stored charge is dumped into an LC tank, forcing it to oscillate at its natural resonance frequency and emitting the energy to an outside receiver. In a pressure sensing configuration, the distance between a planar coil and a ferrite core is modulated by the pressure, thus changing the inductance and in turn inducing a change in the frequency of the emitted signal. A prototype transponder was built and tested using a PZT cantilever with a mechanical resonant frequency of 435 Hz encapsulated in a glass capsule (length=40 mm, diameter=8 mm) along with a rectifier circuitry and a storage capacitor. The inductive pressure sensor located outside the capsule had a sensitivity of 2.5k Hz/kPa. We were able to easily pick up the transmitted RF pulses at distances of up to 7 cm without the tight requirement on alignment between the receiver and the transponder coils.

IEEE Transactions on Biomedical Engineering, 2011

In this paper, we present an ultrasonically powered implantable micro-oxygen generator (IMOG) tha... more In this paper, we present an ultrasonically powered implantable micro-oxygen generator (IMOG) that is capable of in situ tumor oxygenation through water electrolysis. Such active mode of oxygen generation is not affected by increased interstitial pressure or abnormal blood vessels that typically limit the systemic delivery of oxygen to hypoxic regions of solid tumors. Wireless ultrasonic powering (2.15 MHz) was employed to increase the penetration depth and eliminate the directional sensitivity associated with magnetic methods. In addition, ultrasonic powering allowed for further reduction in the total size of the implant by eliminating the need for a large area inductor. IMOG has an overall dimension of 1.2 mm × 1.3 mm × 8 mm, small enough to be implanted using a hypodermic needle or a trocar. In vitro and ex vivo experiments showed that IMOG is capable of generating more than 150 μA which, in turn, can create 0.525 μL/min of oxygen through electrolytic disassociation. In vivo experiments in a well-known hypoxic pancreatic tumor models (1 cm 3 in size) also verified adequate in situ tumor oxygenation in less than 10 min.

In this paper, we report on the first lasermicromachined batch-fabricated single-layer elastomeri... more In this paper, we report on the first lasermicromachined batch-fabricated single-layer elastomeric actuator with a corrugated surface profile. The structural material of the cantilever actuator is a single [polydimethylsiloxane (PDMS)] layer, and electrodes are soft lithographically patterned conductive carbon grease. The asymmetric corrugated surface provides a bending moment in a single PDMS layer without the need for a second inactive layer. An actuator which is 5 mm long, 1 mm wide, and 80 µm thick can generate up to 2-mm out-of-plane displacement with zero applied force and 15 µN at zero deflection while consuming 20 µW of static power when actuated with 500 V.

Journal of Micromechanics and Microengineering, 2011

In this note, we report on the development of a batch-fabricated laser-micromachined elastomeric ... more In this note, we report on the development of a batch-fabricated laser-micromachined elastomeric cantilever actuator composed of a polydimethylsiloxane (PDMS) bilayer (active/inactive) and soft-lithographically patterned conductive carbon grease electrodes. The described unimorph structure has a low actuation voltage and large out-of-plane displacement. For a 4 mm long, 1 mm wide, and 80 µm thick actuator, an out-of-plane displacement of 1.2 mm and a maximum force of 25 µN were measured using 450 V actuation voltage.

IEEE Transactions on Biomedical Engineering, 2012

We report on the development of a batch fabricated biodegradable truncated-cone-shaped plug filte... more We report on the development of a batch fabricated biodegradable truncated-cone-shaped plug filter to overcome the postoperative hypotony in nonvalved glaucoma drainage devices. Plug filters are composed of biodegradable polymers that disappear once wound healing and bleb formation has progressed past the stage where hypotony from overfiltration may cause complications in the human eye. The biodegradable nature of device eliminates the risks associated with permanent valves that may become blocked or influence the aqueous fluid flow rate in the long term. The plug-filter geometry simplifies its integration with commercial shunts. Aqueous humor outflow regulation is achieved by controlling the diameter of a laser-drilled through-hole. The batch compatible fabrication involves a modified SU-8 molding to achieve truncated-cone-shaped pillars, polydimethylsiloxane micromolding, and hot embossing of biodegradable polymers. The developed plug filter is 500 μm long with base and apex plane diameters of 500 and 300 μm, respectively, and incorporates a laser-drilled through-hole with 44-μm effective diameter in the center.

IEEE Electron Device Letters, 2010

ABSTRACT In this letter, we report on a new solid-state structure for an integrating microdosimet... more ABSTRACT In this letter, we report on a new solid-state structure for an integrating microdosimeter. The device consists of a silicon bar enclosed by a compound dielectric bilayer of silicon dioxide/parylene acting as an ionization getter/electret. The dielectric bilayer is corona charged to establish a self-biasing structure that achieves high sensitivity without the need for a large applied voltage. For a 0.5 × 0.7 × 0.3 mm3 sensor with a dynamic range of 15 Gy, a sensitivity of 50 kΩ/Gy was measured.

This paper presents a wireless position and orientation tracking system for radiation therapy. Th... more This paper presents a wireless position and orientation tracking system for radiation therapy. The proposed system uses only four transmitting coils and an implantable wireless transponder. The four transmitting coils generate magnetic field which is sensed and measured by a bi-axial sensor in the transponder in the tumor. A wireless transmitter in the transponder transmits the information back to a computer to determine the position and orientation of the transponder and hence, to track the tumor in real time. The algorithm of tracking is implemented using MATLAB, and simulation results and analysis are presented. Each calculation of the position tracking takes 20 ms, which makes the proposed system suitable for real-time tracking of the transponder for radiation assessment and delivery.