Biosensor

Details Biosensor Biosensor

1999-08-26

2001-10-30

Tung, T. (Department: 1743)

Chemistry: electrical and wave energy

Apparatus

Electrolytic

C204S416000, C427S002130

Reexamination Certificate

active

06309526

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a biosensor for quantifying a specific component contained in a liquid sample. Specifically a method is disclosed for simplifying manufacturing of a biosensor and improving the accuracy of measurement.
BACKGROUND OF THE INVENTION
Among the conventional biosensors is a biosensor for measuring the density of glucose in blood, as disclosed in the Japanese Patent Publication No. 5-256811. The conventional sensor comprises, as shown in
FIG. 3
, leads
2
and
3
formed on an insulating substrate
1
by a screen-printing technology, and a measuring electrode
4
and a counter-electrode
5
, coupled respectively with leads. On the measuring electrode
4
and the counter-electrode
5
is a reagent layer
6
comprised of glucose oxidase as an enzyme, potassium ferricyanide as a mediator, etc.
On the insulating substrate
1
, a cover
10
having an air hole
9
is attached with a spacer
8
having a void
7
at one end in between. These components constitute a biosensor.
For measuring the blood glucose density using a conventional biosensor having the above described constitution, one end of a capillary formed by the void
7
of spacer
8
is placed on blood, then the blood is sucked into the capillary by a capillary phenomenon with the other end of the capillary forming an air hole
9
, and the reagent layer
6
is resolved causing an oxidation/reduction. If a voltage is applied between measuring electrode
4
and counter-electrode
5
, electric current flows in proportion to the density of glucose. The blood sugar level is thus measured.
In the conventional biosensor, carbon is employed as an electrode material suitable for the potassium ferricyanide mediator. The electrode is formed through screen-printing technology.
Namely, a silver paste is screen-printed on substrate
1
for forming the leads
2
and
3
, and a carbon paste is screen-printed to form the measuring electrode
4
and the counter-electrode
5
. Then, in order to regulate the effective area of measuring electrode
4
, a resist layer is formed on the electrode and the leads by screen-printing an insulating paste.
In a conventional manufacturing method wherein a screen-printing process is employed a plurality of times, drying time is needed after each of the steps of paste preparation and screen-printing. The drying thus increases manufacturing time.
Furthermore, in printing the insulating paste, it is inevitable that some paste will ooze out as a result. A wide dispersion in the area of measuring electrode
4
and an adverse influence on the accuracy of response of the finished biosensor will result. Therefore, a need exists to develop a simpler method of providing an measuring electrode, while at the same time enabling a biosensor of higher measuring accuracy to be obtained.
SUMMARY OF THE INVENTION
A biosensor according to the present invention comprises an insulating substrate having a surface which is covered with a metal film. The metal film is split into a plurality of strips. Two covers are placed above the strips. The covers are separated. The portions of the strips between the two covers serve as a measuring electrode and two counter electrodes. The strips at one end of the electrode serve as leads for supplying voltage. A reagent layer is formed between the two covers.
By manufacturing a biosensor as described above, the areas of the measuring electrode and counter-electrode are not dispersed. Therefore, dispersion in response characteristics is reduced.
Furthermore, the upper surface of one of the covers is sealed with a top cover to form a capillary with the openings at both sides of the body of a biosensor. With the above described constitution, as a certain fixed amount of a liquid sample is introduced into the capillary, high accuracy is assured, and as the opening of the capillary is provided at both sides of a biosensor, a liquid sample may be supplied from either side for increased convenience.
Thus, according to the present invention, the area of electrode is defined precisely. In this manner, high accuracy of measurement is obtained. Further, because either opening can be used to supply the liquid sample, high convenience is obtained.


REFERENCES:
patent: 5834224 (1998-11-01), Ruger et al.
patent: 6004441 (1999-12-01), Fujiwara et al.

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