Senol Mutlu

Shaped comb fingers for tailored electromechanical restoring force

Electrostatic comb drives are widely used in microelectromechanical devices. These comb drives often employ rectangular fingers which produce a stable, constant force output as they engage. This paper explores the use of shapes other than the common rectangular fingers. Such shaped comb fingers allow customized force-displacement response for a variety of applications. In order to simplify analysis and design of shaped fingers, a simple model is developed to predict the force generated by shaped comb fingers. This model is tested using numerical simulation on several different sample shaped comb designs. Finally, the model is further tested, and the use of shaped comb fingers is demonstrated, through the design, fabrication, and testing of tunable resonators which allow both up and down shifts of the resonant frequency. The simulation and testing results demonstrate the usefulness and accuracy of the simple model. Finally, other applications for shaped comb fingers are described, including tunable sensors, low-voltage actuators, multistable actuators, or actuators with linear voltage-displacement behavior.

Design and fabrication of two-axis micromachined steel scanners

This paper presents the fabrication and the test results of two-axis micromachined micro-mirror steel scanners developed for display and imaging applications. The novel fabrication method uses the conventional lithography and electrochemical metal etching techniques. A single photomask is used to define the whole structure, resulting in a simple and inexpensive fabrication process. Two different devices are designed, fabricated and characterized to test the proposed methods. Both of them employ the magnetostatic actuation to generate excitation force/torque. First device (Type-A) is a gimballed cantilever one, and it is capable of an optical scanning angle of 11.7° and 23.2° in slow- and fast-scan directions, consuming a power of 42 mW and 30.6 mW, respectively. This structure has a quality factor of 287 in the slow-scan direction and a quality factor of 195 in the fast-scan one. The second device (Type-B) is a gimballed torsional one, and it has an optical scanning angle of 76° and 5.9° in slow- and fast-scan directions, consuming 37 mW and 39 mW, respectively. This structure has a quality factor of 132 in the slow-scan and 530 in the fast-scan directions, respectively. The maximum total optical scanning angles obtained for the slow- and fast-scan axes are 105° (gimballed torsional device, Type-B) and 42° (gimballed cantilever device, Type-A).

Micromachined porous polymer for bubble free electro-osmotic pump

A novel porous polymer was microfabricated to serve as a porous plug for a new device, the porous plug electro-osmotic pump (pp-EOP). The plug eliminates any back pressure effects while enhances electro-osmotic flow in a channel. The pp-EOP was batch fabricated by surface micromachining on top of a silicon wafer. The pp-EOP device is driven by a periodic, zero-average injected current signal at low frequencies producing bubble-free electro-osmotic flow with reversible net movement. Testing of the device produced an average water-air interface velocity of 1.8 /spl mu/m/s at 0.8 Hz. The velocity was increased to 4.8 and to 13.9 /spl mu/m/s by necking the channel size.

A thermally responsive polymer microvalve without mechanical parts photo-patterned in a parylene channel

A photoresist-like thermally responsive polymer has been formulated, surface micromachined and integrated into parylene microchannels to realize an inline valve. The polymer physically swells below its lower critical solution temperature and shrinks above it. Test showed a 2.5-fold polymer volume increase by changing water temperature from 25 to 10/spl deg/C. Repeated polymer swelling and shrinking were observed inside the channel with a system response time around 7 s. Pressure build-up measurements were used to demonstrate the functionality of the valve. Valve test results using DI water showed that the pressure upstream of the polymer plug increased from 15.3 to 20.3 psi with temperature change from 36/spl deg/C to 15/spl deg/C.

An Optically Powered CMOS Receiver System for Intravascular Magnetic Resonance Applications

This paper presents a low-power optically powered receiver system designed in 0.18 μm triple well UMC complementary metal-oxide-semiconductor (CMOS) technology. Optical transmission is used for both power delivery and signal transmission. The power of the whole system can be supplied in two different configurations, namely continuous and intermittent mode configurations. In the continuous mode configuration, the optical power of a 650-nm laser source is received and delivered to the electronic circuits by a set of on-chip CMOS photodiodes. In the intermittent mode configuration, a low voltage DC-DC converter is used to boost a single on-chip CMOS photodiode voltage of 0.65 V up to 1.8 V. Additionally, in this configuration, optical switching is used for charging and discharging of a storage capacitor to obtain currents in milliampere range for the proper operation. The front-end part of the receiver consists of a fully differential low noise amplifier (LNA), a fully differential gain stage, a single output double balanced Gilbert-cell mixer, and a laser driver. The front-end part can operate properly by one on-chip photodiode voltage of 0.65 V . System performance is demonstrated for a sample 1.5 T magnetic resonance imaging (MRI) application. Experiments show that LNA of the receiver has a low input referred noise voltage density of 4 nV/√{Hz} at the supply voltage of 0.65 V . The receiver transmits the signal via a fiber-coupled infrared (IR) laser diode (λ = 1310 nm). The results show that the system can continuously process a minimum detectable signal (MDS) of -70 dBm at an incident optical power of 20 mW while the total power consumption of the receiver and the IR diode is 700 μW . In the intermittent mode configuration, the system gain is measured to be 6 dB greater, and the average power consumption is measured as 214 μW when the incident laser is modulated with a rectangular pulse wave of 40 ms period with 95% duty cycle.

Optical Power Delivery and Data Transmission in a Wireless and Batteryless Microsystem Using a Single Light Emitting Diode

In this paper, a light emitting diode (LED) is used both to harvest energy and to transmit data in a wireless and batteryless microsystem. The microsystem consists of an LED die (350 μm × 350 μm), an application specific integrated circuit (230 μm × 210 μm) and a storage capacitor (0.5 mm × 1 mm) forming a small footprint. A modular optical energy management and data transmission framework is presented. A proof of concept design that transmits a 16-bit identification number serially at a data rate depending on the amount of received optical power is described. The LED has a power efficiency of 22%; better than silicon photodiodes under monochromatic light of 680-nm wavelength. The higher voltage supplied by the LED compared with a silicon photodiode allows circuitry to be powered directly from it without requiring the elevation of the photovoltaic potential, as in the case of using on-chip silicon photodiodes. Data transmission task of the LED requires a charge pump circuit to elevate the photovoltaic voltage. The 0.8 V generated by the LED under a 680-nm laser beam of 4-mW/mm2 optical power density is elevated to 1.4 V for optical transmission at a rate of 4 kbit/s. Under 70-mW/mm2 optical power density, 1.3 V is elevated to 2.4 V, achieving a data rate of 26 kbit/s.

Self-terminating electrochemical etching of stainless steel for the fabrication of micro-mirrors

A novel, self-terminating electrochemical etch process is proposed for the fabrication of scanning steel micro-mirrors. The process uses single mask photolithography, and the etching step is terminated automatically, which at the same time enables the depth profile shaping of the fabricated structure. The proposed process is characterized and then used to fabricate two versions of one-dimensional (1D) steel micro-scanners: one with selective thinning of the predefined parts and one without thinning. The fabricated devices are characterized and compared with respect to their resonance frequencies and mechanical quality factors. The thickness of the starting substrate is selectively thinned down by approximately 150 μ mi n order to decrease the mass of the mirror and eventually to increase the resonance frequency of the fundamental mode. The resonance frequency of the structure is increased from 4210 Hz to 6060 Hz resulting in a normalized frequency shift of 15%. (Some figures in this article are in colour only in the electronic version)

Europe and the Future for WPT: European Contributions to Wireless Power Transfer Technology

This article presents European-based contributions for wireless power transmission (WPT), related to applications ranging from future Internet of Things (IoT) and fifth-generation (5G) systems to high-power electric vehicle charging. The contributors are all members of a European consortium on WPT, COST Action IC1301. WPT is the driving technology that will enable the next stage in the current consumer electronics revolution, including batteryless sensors, passive RF identification (RFID), passive wireless sensors, the IoT, and machine-to-machine solutions. The article discusses the latest developments in research by some of the members of this group.This article presents recent European-based contributions for wireless power transmission (WPT), related to applications ranging from future Internet of Things (IoT) and fifth-generation (5G) systems to highpower electric vehicle charging. The contributors are all members of a European consortium on WPT, COST Action IC1301 (Table 1). WPT is the driving technology that will enable the next stage in the current consumer electronics revolution, including batteryless sensors, passive RF identification (RFID), passive wireless sensors, the IoT, and machine-to-machine solutions.

Advances in microfluidic devices made from thermoplastics used in cell biology and analyses

Silicon and glass were the main fabrication materials of microfluidic devices, however, plastics are on the rise in the past few years. Thermoplastic materials have recently been used to fabricate microfluidic platforms to perform experiments on cellular studies or environmental monitoring, with low cost disposable devices. This review describes the present state of the development and applications of microfluidic systems used in cell biology and analyses since the year 2000. Cultivation, separation/isolation, detection and analysis, and reaction studies are extensively discussed, considering only microorganisms (bacteria, yeast, fungi, zebra fish, etc.) and mammalian cell related studies in the microfluidic platforms. The advantages/disadvantages, fabrication methods, dimensions, and the purpose of creating the desired system are explained in detail. An important conclusion of this review is that these microfluidic platforms are still open for research and development, and solutions need to be found for each case separately.

A solution state diode using semiconductor polymer nanorods with nanogap electrodes

A solution state polymer diode, which uses regioregular poly(3-hexylthiophene-2,5-diyl) (P3HT):dichlorobenzene solution as the semiconductor between highly doped p-type silicon and aluminum electrodes has been built. Electrodes separated by a 40 nm gap enable intra-chain charge carrier transfer through the lengths of single polymer chains. This prevents chain to chain hopping and chain entanglements, increasing carrier mobility. The degradation with time and hysteresis effects of the diodes are measured. An optimal P3HT solution concentration of 6 mg ml(-1) is found. A current density of at least 300 mA cm(-2) is achieved, indicating at least a six-fold improvement in carrier mobility compared to previously fabricated solid state P3HT diodes.