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This paper presents a low-profile and autonomous piezoelectric energy harvesting system consisting of an extraction rectifier and a maximum power point tracking (MPPT) circuit for powering portable electronics. Synchronized switch harvesting on capacitor-inductor (SSHCI) technique with its unique two-step voltage flipping process is utilized to downsize the ponderous external inductor and extend application areas of such harvesting systems. SSHCI implementation with small flipping inductor-capacitor combination enhances voltage flipping efficiency and accordingly attains power extraction improvements over conventional synchronized switch harvesting on inductor (SSHI) circuits utilizing bulky external components. A novel MPPT system provides robustness of operation against changing load and excitation conditions. Innovation in MPPT comes from the refresh unit, which continually monitors excitation conditions of piezoelectric harvester to detect any change in optimum storage voltage. Compared with conventional circuits, optimal flipping detection inspired from active diode structures eliminates the need for external adjustment, delivering autonomy to SSHCI. Inductor sharing between SSHCI and MPPT reduces the number of external components. The circuit is fabricated in 180 nm CMOS technology with 1.23 mm2active area, and is tested with custom MEMS piezoelectric harvester at its resonance frequency of 415 Hz. It is capable of extracting 5.44x more power compared to ideal FBR, while using100μH inductor. Due to reduction of losses through low power design techniques, measured power conversion efficiency of 83% is achieved at 3.2 V piezoelectric open circuit voltage amplitude. Boosting of power generation capacity in a low profile is a significant contribution of the design.

This paper presents a multi-channel piezoelectric acoustic transducer that is working within the audible frequency band (250- 5500 Hz). The transducer consists of eight cantilevers with thin film PLD-PZT piezoelectric layers. The transducer is well suited to be implanted in middle ear cavity with an active volume of 5×5×0.6 mm3and mass of 4.8 mg excluding the test frame. Finite Element Method (FEM) is used for modelling cantilever resonance frequencies and piezoelectric outputs. This model and shaker-table experiments are in good agreement on the frequency (97%) and output voltage (89%) values. Transducer can generate up to 139.36 mVppunder 0.1 g excitation at 316 Hz, which is the highest reported output voltage from a piezoelectric acoustic sensor to the best of our knowledge.

The fully implantable cochlear implant (FICI) interface circuit proposed in this work senses sound harmonics from 8 different piezoelectric cantilever sensors, and generates pulse width modulated biphasic current outputs to stimulate the auditory neurons. Signals from the piezoelectric sensors are amplified, rectified, and sampled. The sampled voltage is held and converted to current by a novel logarithmic voltage-to-current converter. The current is then digitized with a current comparator to determine the width of the generated biphasic current pulses. Continuous interleaved sampling (CIS) is used as the stimulation technique for 8 channels operation. The system is designed and implemented in 0.18 μm HV CMOS process. Measurements show that the circuit is able to generate 15 to 62.5 μs biphasic current pulses with 400 μA peak amplitude, as the input range varies from 60 dB to 105 dB sound pressure level. The total power consumption of 82 and 513 μW have been measured at 70 dB input for 1-channel and have been extrapolated for 8-channels configurations, respectively, which are the lowest powers for FICI interface electronics to the best of our knowledge.

This paper reports the development of a single cantilever thin film PLD-PZT transducer prototype. The device was experimentally characterized by attaching it on an acoustically vibrating membrane resem- bling the behavior of the eardrum. Acceleration characteristic of the sensor attached on the membrane was obtained by using a Laser Doppler Vibrometer (LDV) as the output voltage was measured by an oscil- loscope. A voltage output of 114 mV was obtained, when the device was excited at 110 dB Sound Pressure Level (SPL) at 1325 Hz. This is the highest value for a thin film piezoelectric transducer in the literature to our knowledge. Using the results of a finite element analysis for this single-channel prototype, which are within 92% agreement with the experimental results, we performed an optimization study to propose a multi-frequency acoustic sensor to be placed on the eardrum for fully-implantable cochlear implant (FICI) applications. The proposed multi-channel transducer consists of eight cantilever beams. Each of these beams resonates at a specific frequency within the daily acoustic band (250–5000 Hz), senses the eardrum vibration and generates the required voltage output for the stimulation circuitry. The total volume and mass of the transducer are 5 × 5×0.2 mm3 and 12.2 mg, respectively. High sensitivity of the transducer (391.9 mV/Pa @900 Hz) enables transmission of strong signals to be the readout circuit, which can easily be processed. Expected to satisfy all the requirements (volume, mass, and stimulation signal at the hear- ing band) of FICI applications for the first time in literature, the proposed concept has a groundbreaking nature and it can be referred to as the next generation of FICIs since it revolutionizes the operational principle of conventional CIs.

This paper presents a self-powered interface circuit to extract energy from ambient vibrations for powering up microelectronic devices. The circuit interfaces a piezoelectric energy harvesting micro electro-mechanical systems (MEMS) device to scavenge acoustic energy. Synchronous electric charge extraction (SECE) technique is deployed through the implementation of a novel multistage energy extraction (MSEE) circuit in 180nm HV CMOS technology to harvest and store energy. The circuit is optimized to operate with minimum power losses when input power is limited, and adapts well to operating conditions with higher input power. The highly accurate peak detector was validated for a wide piezoelectric frequency range from 20Hz to 4kHz. A charging efficiency of about 84% has been achieved for 4.75 V open-circuit piezoelectric voltage excited at 390Hz input vibration under nominal input power range of 30–80μW. Power optimizations enable the circuit to maintain a conversion efficiency of 47% at input power level as low as 3.12μW. MSEE provides up to 15% efficiency improvement compared to traditional SECE, and maintains power efficiency as high as possible for a wide input power range.

This paper presents design and fabrication of a MEMS-based thin film piezoelectric transducer to be placed on an eardrum for fully-implantable cochlear implant (FICI) applications. Resonating at a specific frequency within the hearing band, the transducer senses eardrum vibration and generates the required voltage output for the stimulating circuitry. Moreover, high sensitivity of the sensor, 391.9 mV/Pa @900 Hz, decreases the required power for neural stimulation. The transducer provides highest voltage output in the literature (200 mVpp @100 dB SPL) to our knowledge. A multi-frequency piezoelectric sensor, covering the daily acoustic band, is designed based on the test results and validated through FEA. The implemented system provides mechanical filtering, and mimics the natural operation of the cochlea. Herewith, the proposed sensor overcomes the challenges in FICI operations and demonstrates proof-of-concept for next generation FICIs.

This paper presents the first acoustic experimental results of a MEMS based bulk piezoelectric transducer for use in fully implantable cochlear implants (FICI). For this purpose, the transducer was attached onto an acoustically vibrating membrane. Sensing and energy harvesting performances were measured using neural stimulation and rectifier circuits, respectively. The chip has a 150 Hz bandwidth around 1800 Hz resonance frequency that is suitable for mechanical filtering as a sensor. As an energy harvester, bulk piezoelectric transducer generated a rectified power of 16.25μW with 2.47 VDCwith 120 dB-A sound input at 1780 Hz. Among other MEMS acoustic energy harvesters in the literature, reported transducer has the highest power density (1.5 × 10−3W/cm3) to our knowledge.

This is a study of in-plane and out-of-plane distribution of rotational torque (ROT-T) and effective electric field (EEF) on electrorotation (ER) devices with 3D electrodes using finite element modeling (FEM) and experimental method. The objective of this study is to investigate electrical characteristics of the ER devices with five different electrode geometries and obtain an optimum structure for ER experiments. Further, it provides a comparison between characteristics of the 3D electrodes and traditionally used 2D electrodes. 3D distributions of EEF were studied by the time-variant FEM. FEM results were verified experimentally by studying the rotation of biological cells. The results show that the variations of ROT-T and EEF over the measurement area of the devices are considerably large. This can potentially lead to misinterpretation of recorded data. Therefore, it is essential to specify the boundaries of the measurement area with minimum deviation from the central EEF. For this purpose, FE analyses were utilized to specify the optimal region. Thereby, with confining the measurements to these regions, the dependency of ROT-T on the spatial position of the particles can be eliminated. Comparisons have been made on the sustainability of the EEF and ROT-T distributions for each device, to find an optimum design. Analyses of the devices prove that utilization of the 3D electrodes eliminate irregularities of EEF and ROT-T along the z-axis. The Results show that triangular electrodes provide the highest sustainability for the in-plane ROT-T and EEF distribution, while the oblate elliptical and circular electrodes have the lowest variances along the z-axis.

Dielectrophoresis (DEP), a technique used to separate particles based on different sizes and/or dielectric properties under nonuniform electric field, is a promising method to be applied in label-free, rapid, and effective cell manipulation and separation. In this study, a microelectromechanical systems-based, isolated 3D-electrode DEP device has been designed and implemented for the label-free detection of multidrug resistance in K562 leukemia cells, based on the differences in their cytoplasmic conductivities. Cells were hydrodynamically focused to the 3D-electrode arrays, placed on the side walls of the microchannel, through V-shaped parylene-C obstacles. 3D-electrodes extruded along the z-direction provide uniformly distributed DEP force through channel depth. Cell suspension containing resistant and sensitive cancer cells with 1:100 ratio was continuously flown through the channel at a rate of 10 μL/min. Detection was realized at 48.64 MHz, the cross-over frequency of sensitive K562 cells, at which sensitive cells flow with the fluid, while the resistant ones are trapped by positive DEP force. Device can be operated at considerably low voltages (

This paper presents the trapping of imatinib resistant K562 (human chronic myelogenic leukemia (CML), K562/IMA) cells with 3D-electrode contactless dielectrophoresis (DEP). 3D electrodes are isolated from the solution by means of uniform thin parylene layer (~0.3μm), to eliminate the Joule heating, electrolysis, and cell damaging. 3D electrodes (extruded along the microchannel in z-axis) provide uniform distribution of DEP force along the channel height, improving the separation efficiency, significantly. It is verified that the system is capable of trapping K562/IMA cells at a concentration of 6.25×105/ml and 10 μl/min flow rate by applying 9 Vpp sinusoidal signal at 48.64 MHz. No trapping occurs for K562 sensitive cells at the same experimental conditions.

Novel CMOS compatible microchannel heat sinks are designed, fabricated and tested for monolithic liquid cooling of integrated circuits. The proposed heat sink is fabricated by low temperature surface micromachining processes and requires no design change of the electronic circuitry underneath, hence, can be produced by adding a few more steps to the standard CMOS fabrication flow. The microchannel heat sinks were tested successfully under various heat flux and coolant flow rate conditions. The cooling tests have shown that the microchannel heat sinks were able to extract up to 127 W/cm(2) heat flux from a hot spot, and 50 W/cm2 heat flux in steady state continuous operation from the entire heated surface. The obtained Nusselt number correlations fall between two previously proposed correlations for laminar flow in rectangular microchannels. Friction factor results are also in agreement with the laminar theory with slight deviations. (C) 2012 Elsevier Masson SAS. All rights reserved.

This paper presents a novel electrostatically actuated microvalve for lab-on-a-chip applications, fabricated using surface micromachining techniques. Lab-on-a-chip applications generally involve in-plane microflows. Microvalve mentioned here operates by moving a diaphragm, which is in-plane with the flow, perpendicular to the stream with the help of electrostatic forces. Operating principles and the operation of the valve are presented in the paper.

This paper reports a fully implantable, MEMS-based, low-power, energy harvesting, next generation cochlear implant (CI). The implant includes multi-frequency piezoelectric transducers for sound detection and energy harvesting, rectification and signal conditioning electronics, and RF coil for fitting and external powering. These units have outstanding performances: multi-channel transducer can generate 50.7 mVpp (under 100 dB SPL) and recover the daily sound speech signals; signal conditioning IC consumes outstandingly low power (−3W/cm3) with generated 16.25 µW under 120 dB-A sound input; energy harvester IC, provides up to 500% more power compared to an ideal full-bridge rectifier.

This paper presents a novel self-powered and fully autonomous interface circuit to extract piezoelectric energy from vibrations available in the environment for supplying DC voltage to electronic loads. A new energy extraction technique called Synchronized Switch Harvesting on Capacitor-Inductor (SSHCI) is utilized, which reduces system cost through a downsized inductor in the range of tens ofμH’s, while achieving as high voltage flipping efficiency as conventional SSHI circuits. Fabricated in 180 nm standard CMOS technology, the interface circuit has been tested on a MEMS piezoelectric energy harvester with 2 nF intrinsic capacitance in presence of vibrations at 415 Hz resonant frequency. SSHCI circuit provides 6.14x relative improvement over maximum output power of an ideal full-bridge rectifier (FBR) by utilizing a68μHinductor to charge a 453 nF storage capacitance. A maximum power conversion efficiency of 90.1% has been measured for SSHCI operation due to low power design techniques and optimized switching time for charge flipping.