CMOS microelectrode array for bidirectional interaction with neuronal networks

A CMOS metal-electrode-based micro system for bidirectional communication (stimulation and recording) with neuronal cells in vitro is presented. The chip overcomes the interconnect challenge that limits today's bidirectional microelectrode arrays. The microsystem has been fabricated in an industrial CMOS technology with several post-CMOS processing steps to realize 128 biocompatible electrodes and to ensure chip stability in physiological saline. The system comprises all necessary control circuitry and on-chip A/D and D/A conversion. A modular design has been implemented, where individual stimulation- and signal-conditioning circuitry units are associated with each electrode. Stimulation signals with a resolution of 8 bits can be sent to any subset of electrodes at a rate of 60 kHz, while all electrodes of the chip are continuously sampled at a rate of 20 kHz. The circuitry at each electrode can be individually reset to its operating point in order to suppress artifacts evoked by the stimulation pulses. Biological measurements from cultured neuronal networks originating from dissociated cortical tissue of fertilized chicken eggs with amplitudes of up to 500 /spl mu/V/sub pp/ are presented.     

Switch-Matrix-Based High-Density Microelectrode Array in CMOS Technology

We report on a CMOS-based microelectrode array (MEA) featuring 11,011 metal electrodes and 126 channels, each of which comprises recording and stimulation electronics, for extracellular bidirectional communication with electrogenic cells, such as neurons or cardiomyocytes. The important features include: (i)$~$high spatial resolution at (sub)cellular level with 3150 electrodes per mm$^{2}$ (electrode diameter 7 $mu$ m, electrode pitch 18$ mu$m); (ii) a reconfigurable routing of the recording sites to the 126 channels; and (iii) low noise levels.      

CMOS monolithic mechatronic microsystem for surface imaging and force response studies

We report on a standalone single-chip (7 mm /spl times/10mm) atomic force microscopy (AFM) unit including a fully integrated array of cantilevers, each of which has individual actuation, detection, and control units so that standard AFM operations can be performed only by means of the chip without any external controller. The system offers drastically reduced overall size and costs and can be fabricated in standard CMOS technology with some post-CMOS micromachining steps to form the cantilevers. Full integration of microelectronic and micromechanical components on the same chip allows for controlling and monitoring all system functions. The on-chip circuitry notably improves the overall system performance. Circuitry includes analog signal amplification and filtering stages with offset compensation, analog-to-digital converters, digital proportional-integral-derivative (PID) deflection controllers, sensor-actuator compensation (SAC) filters, and an on-chip digital interface for data transmission. The microsystem characterization evidenced a vertical resolution of better than 1 nm and a force resolution of better than 1 nN as shown in the measurement results. This CMOS monolithic AFM microsystem allows for precise and fully controlled mechanical manipulation in the nanoworld.     

CMOS-Based Monolithic Controllers for Smart Sensors Comprising Micromembranes and Microcantilevers

This paper presents design considerations and implementations of monolithic controllers for smart sensors that make use of micromachined structures such as micromembranes and microcantilevers. Five control techniques are reviewed, and the classic control technique is selected for the design of the controllers. The circuit implementations of an analog proportional controller and a digital proportional-integral-derivative controller are described in detail. The first controller is used for controlling the microhotplate (micromembrane) temperature of a monolithic metal-oxide gas sensor array. The second controller is used for controlling the microcantilever deflection of a monolithic atomic force microscope. The controllers and microsensors are fabricated in standard 0.8-mum CMOS technology combined with post-CMOS micromachining. Chemical measurements and contact-mode imaging are performed to confirm the excellent performance of these monolithic controllers     

Beamspace adaptive beamforming for ultrasound imaging

Applying the Capon adaptive beamformer in medical ultrasound imaging results in enhanced resolution by improving the interference-suppressing capabilities of the array. This improvement comes at the expense of an increased computational complexity. We have investigated the application of a beamspace adaptive beamformer for medical ultrasound imaging, which can be used to achieve reduced computational complexity with performance comparable to that of the Capon beamformer. The idea behind beamspace beamforming is that, instead of using the spatial statistics of the elements in the array to differentiate between signals and interference, we use the spatial statistics of a set of orthogonal beams, which are formed in different directions. This represents a shift from element space to beamspace. Because the majority of interference in medical ultrasound imaging is constrained to a limited spatial interval due to the focused transmit beam, this latter space can be reduced to a dimension that is lower than that of element space. We show, using simulations and experimental data, that this dimension can be selected as low as 3 while still achieving performance comparable to its element space counterpart.     

Validation of X-ray lithography and development simulation system for moving mask deep X-ray lithography

This paper presents a newly developed 3-Dimensional (3-D) simulation system for Moving Mask Deep X-ray Lithography (M/sup 2/DXL) technique, and its validation. The simulation system named X-ray Lithography Simulation System for 3-Dimensional Fabrication (X3D) is tailored to simulate a fabrication process of 3-D microstructures by M/sup 2/DXL. X3D consists of three modules: mask generation, exposure and resist development (hereafter development). The exposure module calculates a dose distribution in resist using an X-ray mask pattern and its movement trajectory. The dose is then converted to a resist dissolution rate. The development module adopted the "Fast Marching Method" technique to calculate the 3-D dissolution process and resultant 3-D microstructures. This technique takes into account resist dissolution direction that is required by 3-D X-ray lithography simulation. The comparison between simulation results and measurements of "stairs-like" dose deposition pattern by M/sup 2/DXL showed that X3D correctly predicts the 3-D dissolution process of exposed PMMA.