In this paper, we report the use of polysilicon ͑poly-Si͒ wire for label-free DNA sequence detection. Both single-strained ͑ss͒ homopolymers, polyadenine ͓poly͑A͔͒, polythymine ͓poly͑T͔͒, polycytosine ͓poly͑C͔͒, and polyguanine ͓poly͑G͔͒, and doublestranded ͑ds͒ heteropolymers ͑one homopolymer with its complement homopolymer͒, ͑A-T͒ ͓poly͑A-T͔͒ and ͑C-G͒ ͓poly͑C-G͔͒, were detected. These polymers, with different lengths and concentrations, were dropped onto the poly-Si wire surface, and then the currents flowing through the poly-Si wire channel were determined. The absolute value of the amount of current change ⌬I in the channel for ss homopolymers with fixed length and fixed concentration is as follows: poly͑T͒ Ͼ poly͑C͒ Ͼ poly͑G͒ Ͼ poly͑A͒. For ds heteropolymers, it was observed that poly͑A-T͒ has a ⌬I that is higher than that of poly͑C-G͒. This study also showed that the poly-Si wire is useful for detecting single-and multiple-base changes in the ss homopolymers as well as singleand multiple-matched-pair changes in ds heteropolymers. A single-pair mismatch in ds poly͑C-G͒ was also investigated in this work.The determination of DNA sequences has long been a topic of intensive research in biotechnology and medical diagnostics because the genetic information carried by an organism is inscribed in its DNA. In addition, the measurement of DNA conductivity, hybridization, and melting by electronic means has drawn a great deal of attention in recent years due to its possible applications in molecular electronics. 1-3 A DNA sequence is typically determined by using radiochemical, enzymatic, and fluorescent techniques, 4,5 in which labels or reagents are added into the molecules that are being tested and detected. These techniques are usually time-consuming, expensive, and complicated to implement. Therefore, label-free DNA detection methods such as cyclic voltammetry and chronopotentiometry were developed. 6-9 However, these label-free methods are of wet type, where the sensor has to be immersed in the solution being tested, and hence the selectivity as well as the detection limit of the sensor is influenced by the thermal drift of the electrolyte solution. [10][11][12] As a result of the rapid progress in semiconductor fabrication technologies, many semiconductor/nanodevices and measurement tools have been developed either to measure the electrical properties of DNA or to detect DNA. [13][14][15][16][17][18][19] For example, Storm and his coworkers used nanogap junctions to measure the electrical resistance of hybridized and denatured DNA molecules. 13 Zwolak and Di Ventra used nanopores to observe the different chemical structures of the four different bases of DNA and proved that each of the four bases of DNA carries a unique electronic and chemical structure. 14 This result was later confirmed by Xu and his co-workers by measuring the current flowing through DNA with a scanning probe microscope ͑SPM͒. 16 However, the aforementioned nanopore device is difficult to fabricate and the SPM is very expensive.At the same...