Particle detection using an integrated capacitance sensor

• Published in: Sensors and actuators. A, Physical Vol. 92; no. 1; pp. 74 - 79
• Main Authors: York, T.A., Evans, I.G., Pokusevski, Z., Dyakowski, T.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Lausanne Elsevier B.V 01.08.2001; Elsevier Science
• Subjects: Biological and medical sciences; Capacitance sensor; Circuits and circuit components; Circuits ans circuit components; Electrical and electronic components, instruments and techniques; Electrical impedance tomography (EIT); Exact sciences and technology; General equipment and techniques; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Integrated particle detector; Investigative techniques, diagnostic techniques (general aspects); Medical sciences; Miscellaneous. Technology; Pathology. Cytology. Biochemistry. Spectrometry. Miscellaneous investigative techniques; Physics; Tomography; Transducers; Capacitance sensor; Integrated particle detector; Tomography; Performance evaluation; Finite element method; Circuit design; Computational fluid dynamics; Capacitive transducer; Particle detectors; Integrated system; Modelling; Experimental study; Chip; Charge measurement
• ISSN: 0924-4247; 1873-3069
• DOI: 10.1016/S0924-4247(01)00542-8

Capacitance sensors, for detecting small particles, have been integrated onto a custom CMOS VLSI chip. The sensors employ a charge measuring circuit and differential amplifier which depend strongly on close matching of components for correct operation. Finite element modelling has revealed the magnitude of anticipated capacitance changes which, for particles on the surface of the chip, may be of the order of a femtofarad. Simulations using computational fluid dynamics (CFD) suggest that, if the sensor is inclined to the flow, the particles can be expected to hit the surface. Consideration of the surface of the chips suggest that surface roughness is not significant. Static tests reveal output voltage changes of several hundred millivolts in the presence of small particles on the surface. This drops dramatically as particles are moved vertically away from the surface. Dynamic tests confirm that the sensor is able to detect plastic particles as small as 20 μm that are carried at velocities up to about 10 m/s with a time resolution of 2 μs. Recent work has involved the capture of high speed video images of particles passing the chip in order that we can verify correct operation of the sensor. Representative video images are presented.