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This work presents CMOS micromachined dielectric cantilevers with integrated sharp tips for surface temperature measurement. The integrated cantilever can perform electrothermal actuation and piezoresistive sensing for maintaining a proper tip–sample contact. For a cantilever 280 µm long, the measured thermoelectric power from the aluminum/polysilicon thermocouple is 22.6 ± 0.36 µV °C−1, the measured time constant is 796 µs, and the drift due to thermal actuation is 0.15 ± 0.057 µV °C−1. The measured displacement by thermal actuation is 2.2 µm at 17.8 mW and the measured thermal time constant is 79.6 µs. The measured piezoresistive sensitivity and pre-amp noise are 0.48 mV µm−1and 0.7 µV Hz−1/2, respectively, producing an equivalent input-referred noise displacement of 1.45 nm Hz−1/2.

This paper presents the design, fabrication and characterization of CMOS (complementary metal oxide semiconductor) micromachined grippers with on-chip photo detectors placed beneath the gripping sites. The fabrication features a combination of metal wet etch and sacrificial polysilicon etch for structural release. The fabricated microstructure contains metal and dielectric layers, plus a polysilicon heater for electrothermal actuation. For an applied power of 6 mW, one arm of the gripper produces a 3.6 µm in-plane displacement and a 1.6 µm out-of-plane displacement. The corresponding heater temperature is 220 °C, and the temperature elevation at the tip is only 28 °C. The measured sensitivity and dynamic range of the photo detector are 1.42 V lux−1 s and 48.5 dB, respectively. For measurements with and without grabbing a polystyrene bead, the difference of sensed voltages is 0.06 V at 100 lux.

In this paper, we present the design, fabrication and characterization of CMOS micromachined probes for extracellular neural recording. A convenient fabrication process is proposed for making integrated recording probes at the die level, providing a low-cost solution for academic research as compared to the more expensive wafer-level approach adopted in prior work. The devices are fabricated in a standard 0.35 µm CMOS process, followed by post-CMOS micromachining steps to form the probes. The on-chip circuit, used for recording action potential signals of neural activities, provides a stable dc bias when operating in electrolyte. The subthreshold transistor at the circuit input provides a tunable resistance value between 10 MΩ up to GΩ. The circuit consumes a total power of 790 µW and has an output noise of 19.3 µV Hz−1/2 at 100 Hz. The recorded action potential from the stimulated ventral nerve cord of a crayfish is about 0.6 mV with a pulse width of about 1.2 ms.

In this paper, we present the design, fabrication and characterization of the CMOS micromachined cantilevers for mass sensing in the femtogram range. The cantilevers consisting of multiple metal and dielectric layers are fabricated after completion of a conventional CMOS process by dry etching steps. The cantilevers are electrostatically actuated to resonance by in-plane electrodes. The mechanical resonant frequency is detected capacitively with on-chip circuitry, where the modulation technique is applied to eliminate capacitive feedthrough from the driving port and to lessen the effect of flicker noise. The highest resonant frequency of the cantilevers is measured at 396.46 kHz with a quality factor of 2600 at 10 mTorr. The resonant frequency shift after deposition of a 0.1 µm SiO2 layer is 140 Hz, averaging 353 fg Hz−1.

In this paper, we describe the design and characterization of a CMOS micromachined suspended structure with a PMOS transistor operated in the subthreshold region for thermal sensing. The sensor has an area of 70 µm by 70 µm and the sensing transistor is placed inside a suspended plate of 50 µm by 50 µm. The device is fabricated by successive dry etching steps on a CMOS die. For device characterization, each sensor has an embedded polysilicon heater capable of providing a heating efficiency of 0.84 °C mW−1. The measured MOS output resistance changes from 108.3 MΩ to 90.4 MΩ for a temperature rise of 5.5 °C, which is equivalent to a measured temperature coefficient of resistance −3% °C−1, much better than the value of transistors operated in saturation. The measured input-referred noise voltage from the pre-amp is 7 µV Hz−1/2, equivalent to an input-referred noise temperature of 14.9 mK Hz−1/2.

Resonant sensing has been used to detect various physical or chemical quantities, however many reported sensing systems are still bulky and expensive as they rely on external instruments to conduct measurements. For practical applications, it is often desirable to have a low-cost miniaturized sensor chip with multiple sensing devices. This paper presents the first attempt to implement a capacitive resonant sensor array in a complementary metal oxide semiconductor process. The damping loss of all sensors is compensated by placing them in an oscillator loop that contains a phase-locked loop (PLL) driving circuit. The inclusion of a PLL is beneficial for sustaining the oscillation of various resonant frequencies due to the manufacturing tolerance and detected quantity within the PLL capture range. The fabricated micromechanical resonators have a resonant frequency near 200 kHz. To evaluate the sensor performance, a parylene-D thin film was deposited on microstructures and the corresponding frequency shift of 12 devices was on average 33.87 kHz. The resolution for mass detection was estimated to be 23 pg.

The glass-based low-temperature polycrystalline-silicon (LTPS) thin-film transistor (TFT) process, widely known for making liquid crystal displays, is utilized in this work to realize a fully integrated, microbead-based micro-manipulation and biosensing platform. The operation utilizes arrays of microelectrodes made of transparent iridium tin oxide (ITO) to move the immobilized polystyrene microbeads to the sensor surface by dielectrophoresis (DEP). Detection of remaining microbeads after a specific antigen/antibody reaction is accomplished by photo-detectors under the transparent electrodes. It was found that microbeads can be driven successfully by the 30???30??m2?microelectrodes separated by 10??m with no more than 6?Vp?p, which is compatible with the operating range of thin-film transistors. Microbeads immobilized with antimouse immunoglobulin (IgG) and prostate-specific antigen (PSA) antibody were successfully detected after specific binding, illustrating the potential of LTPS TFT microarrays for more versatile biosensing applications.

This work describes the design and characterization of integrated CMOS (complementary metal oxide semiconductor) oscillators comprising a capacitively transduced micromechanical resonator and a phase-locked loop (PLL) driving circuit. Three oscillator schemes are studied and compared, including direct feedback, direct feedback containing a PLL and hybrid direct feedback plus a PLL. PLL is known for its capability in automatic tuning and tracking of a reference signal. Inclusion of a PLL is beneficial for sustaining oscillations at resonant frequencies within its capture range. The micromechanical resonator has a measured resonant frequency of 117.3 kHz. The CMOS PLL circuit has a closed-loop bandwidth of 1.8 kHz with a capture range between 111 kHz and 118.4 kHz. The start-up times for oscillation are shortened in the two schemes utilizing a PLL, since it provides an initial driving signal at its free-running frequency. The lock-in time is also reduced by increasing the proportion of PLL drive in the hybrid scheme. The measured noises for the three oscillator schemes are similar with a value of −75 dB below the resonant peak at a 10 Hz offset.

This paper describes the design, fabrication and characterization of a complementary metal-oxide-semiconductor (CMOS) micro-electro-mechanical-system (MEMS) accelerometer implemented in a 0.18 µm multi-project wafer (MPW) CMOS MEMS process. In addition to the standard CMOS process, an additional aluminum layer and a thick photoresist masking layer are employed to achieve etching and microstructural release. The structural thickness of the accelerometer is up to 9 µm and the minimum structural spacing is 2.3 µm. The out-of-plane deflection resulted from the vertical stress gradient over the whole device is controlled to be under 0.2 µm. The chip area containing the micromechanical structure and switched-capacitor sensing circuit is 1.18 × 0.9 mm2, and the total power consumption is only 0.7 mW. Within the sensing range of ±6 G, the measured nonlinearity is 1.07% and the cross-axis sensitivities with respect to the in-plane and out-of-plane are 0.5% and 5.8%, respectively. The average sensitivity of five tested accelerometers is 191.4 mV G−1with a standard deviation of 2.5 mV G−1. The measured output noise floor is 354 µG Hz−1/2, corresponding to a 100 Hz 1 G sinusoidal acceleration. The measured output offset voltage is about 100 mV at 27 °C, and the zero-G temperature coefficient of the accelerometer output is 0.94 mV °C−1 below 85 °C.

This paper presents the integration of interdigitated microelectrodes and a CMOS circuit for electrochemical sensing of the neurotransmitter dopamine. Gold electrodes with a gap of 3 µm are fabricated by the lift-off technique. The CMOS sensing circuit has a current gain of 10, an integrating capacitor of 4 pF, and a measured dynamic range of 60 dB. The applied reduction and oxidation potentials are determined by voltammetry at about −0.2 V and 0.6 V, respectively. The measured collection efficiency can reach up to 84%. The produced oxidation current with respect to dopamine concentration averages 0.44 nA µM−1.

This work presents a CMOS micromachined capacitive sensor for the detection of acoustic pressure transmitted through the air. The microstructure has a suspended plate of 65 µm in diameter that produces a sensing capacitance of 35 fF and a resonant frequency of 1.2 MHz. The post-CMOS fabrication can effectively reduce the parasitic capacitance to enhance the signal-to-noise ratio. The measured input-referred circuit noise is 0.35 µV Hz1/2 at 40 kHz. The measured sensor output is 3.5 µV under a dc bias of 10 V, equivalent to a capacitance change of 1.7 × 10−2 aF. The corresponding electrode displacement and acoustic pressure are 4.1 × 10−2 A and 1.3 Pa, respectively.