**1. Introduction**

In view of the growing concerns about such issues as food security, health care, evidencebased care, infectious disease, and tailor-made medicine, a portable gene-based point-ofcare testing (POCT) system is needed. For a system that anyone can operate anywhere and obtain immediate results, a new biosensor chip must be developed. Electrical detection us‐ ing complementary metal-oxide semiconductor (CMOS) integrated circuits has great poten‐ tial since it eliminates the labeling process, achieves high accuracy and real-time detection, and offers the important advantages of low-cost, compact equipment.

**Figure 1.** Integrated sensor array. (a) Matrix array arrangement where *W* and *B* are word and bit lines, respectively. (b) Schematic cross section of a sensor cell where n+ and p+ are heavily doped n-type and p-type semiconductors, respec‐ tively, and n-well is the n-type semiconductor region.

Our target is a monolithically integrated sensor array, as shown in Figure 1(a), which detects all possible biomolecular interactions simultaneously. In each sensor cell, different kinds of

© 2013 Nakazato; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2013 Nakazato; licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

probes can be formed for parallel detection. In addition, the same kind of probe can be used to observe the time evolution of the spatial distribution of biomolecular interactions as well as to improve the detection accuracy since biomolecular interactions are a stochastic process. In this paper, several biosensor arrays are described based on the detection of electric poten‐ tial, current, capacitance, and impedance.
