Bogdan Firtat

Micromachining of a silicon multichannel microprobe for neural electrical activity recording

The cellular potential recording permits the investigation of the central nervous activity. The paper presents the design and manufacturing steps of an eight-channel microprobe for recording the electrical activity of neural cells and tissues integrated on the same chip with the electronics. The specific fabrication processes of the integrated microprobe are presented. An implantable neural microprobe is developed to enable the correlation between electrical activity in the human nervous system and externally psycho-electrical stimuli.

Silicon micromachined sensor for gas detection

The paper presents the layout and the technological steps for an interdigitated integrated capacitor used for gases detection. Silicon micromachining technology is applied for manufacturing the sensor substrate. The sensitive layer used is phthalocyanine (Pc) deposed by evaporation technique under high vacuum. The phthalocyanine derivatives are obtained by the same deposition technique. Considering the different sensitivities of phthalocyanines derivatives, we obtained different gas sensors. The copper phthalocyanine (CuPc), nickel phthalocyanine (NiPc) and iron phthalocyanine (FePc) have been investigated for NO x detection. The measurement of sensors for NO, and NO 2 detection will be presented as gas concentration versus impedance. The microsensors testing structures deposited with phthalocyanines were investigated by impedance measurements in a vacuum chamber controlled by a gas analyser. The measurements were made at room temperature but a medium temperature is applied (<200 °C) after measurement, for cleaning the material in order to reuse the sensor. The sensor is integrated, MOS compatible, cheap, easy to be used and has a low power consumption.

Nanostructured SnO2–ZnO composite gas sensors for selective detection of carbon monoxide

A series of SnO2–ZnO composite nanostructured (thin) films with different amounts of SnO2 (from 0 to 50 wt %) was prepared and deposited on a miniaturized porous alumina transducer using the sol–gel and dip coating method. The transducer, developed by our research group, contains Au interdigital electrodes on one side and a Pt heater on the other side. The sensing films were characterized using SEM and AFM techniques. Highly toxic and flammable gases (CO, CO2, CH4, and C3H8) were tested under lab conditions (carrier gas was dry air) using a special gas sensing cell developed by our research group. The gas concentrations varied between 5 and 2000 ppm and the optimum working temperatures were in the range of 210–300 °C. It was found that the sensing performance was influenced by the amount of oxide components present in the composite material. Improved sensing performance was achieved for the ZnO (98 wt %)–SnO2 (2 wt %) composite as compared to the sensors containing only the pristine oxides. The sensor response, cross-response and recovery characteristics of the analyzed materials are reported. The high sensitivity (R S = 1.21) to low amounts of CO (5 ppm) was reported for the sensor containing a composite sensitive film with ZnO (98 wt %)–SnO2 (2 wt %). This sensor response to CO was five times higher as compared to its response to CO2, CH4, and C3H8, thus the sensor is considered to be selective for CO under these test conditions.

ISFET Microsensors HfO2 Based for Biomedical Applications

The sensor presented in the paper is based on ion selective field effect transistors to detect chemical quantities from biological media (Arshak Poghossian, 2004). The micromachining techniques used for realisation of the chemical sensors dedicated to pH, Na+, K +, H+ detection using silicon micromachined transducers and sensitive layers as HfO2 are presented. The silicon transducers are realised by micromachining techniques (both surface and bulk) and the sensitive layer (in the area of nm thickness) is deposited on top of the wafers allowing the sensors HfO2 based realisation. HfO2 is a material characterised by high dielectric constant and its characteristics in terms of gate material for ISFET sensors are presented. The electrical and functional characterisation of sensors are presented. The major achievements of the work are: manufacturing a CMOS compatible ISFET based on chemical sensitive layers for biological and medical applications; integration of the ISFET sensors on the tip of a microprobe that can be used for measurements of different chemical species (pH, Na+, K+ , H+) in vivo and in vitro and the development of a new sensing material (HfO22); compatibility of all technological process with CMOS technologies and development of new packaging methods

Simulation, design and microfabrication of multichannel microprobe for bioelectrical signals recording

The extracellular potential simultaneous recording permits the investigation of the central nervous activity. The paper presents the design and manufacturing steps of a five electrodes microprobe for recording the electrical activity of neural cells and tissues integrated on the same chip with the electronics. The specific fabrication processes of the integrated microprobe are presented. An implantable neural microprobe is going to be developed to enable the correlation between electrical activity in the human nervous system and externally psychoelectrical stimuli. The electronics accomplish the separation and reduction of the biological noise recording.

Differential Piezoresistive Pressure Sensor

The pressure microsensor presented in this paper is based on a thin, elastic membrane, with boron implanted piezoresistive elements included, positioned in the maximum mechanical stress areas on the membrane. The pressure range for the developed sensors is in the 0divide400 mbar range, and this is the main novelty of this device. The optimized design and technological steps offer high efficiency, sensitivity and reliability to the developed pressure sensor.

Technology of a nanowire bioFET device for biomolecules detection

The paper is presenting the technology of a nanowire FET device to be used in biodetection. The nanosensor we are presenting is containing a FET device realized on top of a silicon wafer substrate with a long nanowire allowing the conduction between source and drain and hosting the specific biomaterial on top of it.(nanowire bioFET)

Phtalocyanine based integrated gas sensor

This paper presents the layout and the technological steps for an interdigitally integrated capacitor used for gas detection. Silicon micromachining technology is applied for manufacturing the sensor substrate. The sensitive layer used is phthalocyanine (Pc) deposed by EDL (evaporated dyes layers technique). Many solutions were found using the phthalocyanine derivatives deposition technique. Considering the different sensitivities of phthalocyanines derivatives, we obtained different gas sensors. The copper phthalocyanine (Cu Pc) and nickel phthalocyanine (Ni Pc) have been investigated for NO/sub x/ detection. The measurement of sensors for NO/sub x/ and NH/sub 3/ detection are presented as concentration versus impedance. The microsensor testing structures deposited with phthalocyanines were investigated by impedance measurements in a vacuum chamber controlled by a gas analyzer. The measurements were made at room temperature but a medium temperature is applied (< 200/spl deg/C) after measurement, for cleaning the material in order to reuse the sensor. The sensor is integrated, MOS compatible, cheap, easy to use and has low power consumption.

Miniaturized Integrated Platform for Electrical and Optical Monitoring of Cell Cultures

The following paper describes the design and functions of a miniaturized integrated platform for optical and electrical monitoring of cell cultures and the necessary steps in the fabrication and testing of a silicon microchip Micro ElectroMechanical Systems (MEMS)-based technology for cell data recording, monitoring and stimulation. The silicon microchip consists of a MEMS machined device containing a shank of 240 μm width, 3 mm long and 50 μm thick and an enlarged area of 5 mm × 5 mm hosting the pads for electrical connections. Ten platinum electrodes and five sensors are placed on the shank and are connected with the external electronics through the pads. The sensors aim to monitor the pH, the temperature and the impedance of the cell culture. The electrodes are bidirectional and can be used both for electrical potential recording and stimulation of cells. The fabrication steps are presented, along with the electrical and optical characterization of the system. The target of the research is to develop a new and reconfigurable platform according to the particular applications needs, as a tool for the biologist, chemists and medical doctors working is the field of cell culture monitoring in terms of growth, maintenance conditions, reaction to electrical or chemical stimulation (drugs, toxicants, etc.). HaCaT (Immortalised Human Keratinocyte) cell culture has been used for demonstration purposes in order to provide information on the platform electrical and optical functions.

Sensor system for on-line monitoring of cell cultures

The paper is presenting the development of a sensor system dedicated to monitor the environment of eukaryotic cells culture acting as biosensors for toxins detection. The system we are presenting is containing pH, and temperature sensors integrated into microfluidic channels.