Paulo José Abatti

Measurement of human red blood cell deformability using a single micropore on a thin Si/sub 3/N/sub 4/ film

The filtration method for the evaluation of the red blood cell (RBC) deformability has been further refined to simulate the deformations encountered in the reticuloendothelial system (in particular the spleen). The core of the measuring system is a very thin (0.4 mu m thick) filter that consists of a single micropore (diameters down to 1 mu m) on a Si/sub 3/N/sub 4/ film which has been constructed using silicon microfabrication techniques. Individual RBC deformability is quantified by measuring the cell pore passage time. From one blood sample 200 passage times were analyzed by a computer, displaying mean and median values as deformability indexes, and class and cumulative histograms for studying the passage times distribution. The effectiveness of the system as a routine clinical evaluation tool is demonstrated by studying several factors that are known to affect the RBC deformability. It is experimentally demonstrated that the human RBC can traverse a pore with a diameter as small as 1 mu m when the pore length is very short.<<ETX>>

Design of coils for millimeter- and submillimeter-sized biotelemetry

Biotelemetric systems, especially those that employ implanted devices, work with inductive links, where usually large circular external coils are separated by relatively large distances (dimensions of centimeters) from the small (millimeter- or submillimeter-size) implanted coils. This paper shows that, under these conditions, a simplified method for calculation of the mutual inductance (M) between the coils, avoiding elliptic integrals, can be obtained. A procedure for coil design, with maximum M between them, is also described.

A Novel Method to Read Remotely Resonant Passive Sensors in Biotelemetric Systems

Resonant passive sensors composed by resistive, inductive, and capacitive (RLC) simple sensors are widely used in biotelemetric systems. In this paper, a novel method to read remotely these RLC sensors is presented. The developed method is based on the simultaneous application of three excitation signals of same amplitudes, set at different frequencies, to determine remotely the RLC sensor resonance frequency and quality factor . Theoretical analysis and experimental results are also presented.

Electrical Characteristics of the Sparks Produced by Electrosurgical Devices

The electrical characteristics of the sparks produced between the active electrode and the biological tissue during electrosurgical procedures have been experimentally investigated. The results have shown that the minimum voltage required to initiate a spark depends on the applied voltage polarity resulting in electrosurgical voltage asymmetry. This voltage asymmetry is capable of producing DC levels that can result in tissue electrostimulation or direct current burns as discussed in this paper. The experimental setup and the conditions, under which the results have been obtained, including the techniques used to improve experimental reproducibility, are reported in detail.

Biotelemetric passive sensor injected within tendon for strain and elasticity measurement

A passive and injectable (using hypodermic needle) biotelemetric sensor for measurements of tendon length changes has been developed. From these measurements tendon strain and Youngs modulus of elasticity can be derived. The sensor(about 2.1 times 29mm) is a LC circuit fixed in tendon by metallic anchors (barbs), where the value of the resonance frequency is modulated by displacement of a mobile ferrite core. The sensor was injected into digital extensor tendon of pig,allowing the determination of its stress-strain curve and, consequently, of Youngs modulus of elasticity of the tendon. Practical results, such as sensitivity of 18.199kHz/mm (correlation coefficient of 0.9891)for strains up to 5.17%, mechanical hysteresis of 6.5%, and Youngs modulus of 0.9146 GPa for a pig tendon (post mortem),are presented and discussed

Stable Potential Oscillation of Lipid Membrane Supported by a Micropore

A rhythmic, sustained, stable potential oscillation was reproducibly observed for a lipid membrane supported by a micropore of a thin membrane tip micropipette. Amplitude and period of the oscillation voltage was controlled by changing the pore diameter. The relationship between oscillation period and pore diameter when the pore diameter was below 8 µm was different from that when the diameter was larger than 8 µm.

Development of a new geometrical form of micropipette: electrical characteristics and an application as a potassium ion selective electrode

Using a mix of thermal and anodic bonding together with microlithographic techniques, the safe transference of a Si/sub 3/N/sub 4/ film with a pore (diameter down to 1 mu m) to a glass tube tip (external diameter 800 mu m) was accomplished, yielding a new geometrical form of micropipette. Compared with conventional glass micropipettes the device has shown lower resistance, more stable capacitance (independent of the tip immersion depth), tip potential closer to that of a salt bridge, and a simplified filling process. Using this device as a potassium ion selective electrode (ISE), a faster response time ISE was achieved. These features indicate that the new device can advantageously substitute the conventional glass micropipettes when cell impalement is not required.<<ETX>>

Distance Measurement With Inductive Coils

Distance measurement is an important tool in several applications. This article describes the development of a resonant inductive sensor for short (few centimeters) distance measurement. The sensor uses the principle of inductive coupling, where a transmitter coil (TX) induces a voltage in receiver coil (RX). The distance between TX and RX coils is determined as a function of the amplitude of the induced signal. Both coils are controlled by processing circuits and a microcomputer performs information processing and stores the measured data. In a setup for distances between 100-240 mm, experimental results showed a maximum standard deviation (σ) of 2.56 mm at 235 mm.

Membrane oscillator as a chemical sensor - Part 1: Fabrication of TM pipet

A rhythmic, sustained, stable oscillation was reproducibly observed for a lipid membrane supported by a micropore of a thin membrane tip micropipet (TM pipet). The construction of the TM pipet was accomplished by implementing a microfabrication method that allowed the transference of a Si3N4 film with a hole from the Si substrate to the glass tube tip. The main part of the fabrication method is the sealing process: a mix between thermal and amodic bonding. The TM pipet fabrication is described in detail with emphasis on the thermal-anodic bonding process. In addition, a general account of the new devices main features, including various applications, is given.