Development of high Tc SQUID microscope for biological application

在这项研究中，我们开发了用于生物应用的高Tc SQUID磁显微镜系统。我们的结果按以下顺序概括：1.我们开发了高性能SQUID实用的双螺旋关节与30度偏置角度。At 77 K， we can routinely obtain the voltage modulation depth？V>20？V and the flux noise S？D2？D11/2？D1<12？D2？D2/Hz？D1 for 100 pH-SQUID. 2。我们显著地降低了直接耦合磁体的1/f噪声。如果要避免在拾取线圈中进行通量陷阱，我们就开发出一个拾取线圈，它是由4个平行环组成的窄线宽度和影响到So-called通量大坝。With this pickup coil， the flux noise is reduced to S-D2-D11/2-D1=23-D2 o-D2/Hz-D11/2-D1 at f=1 Hz。This values is only 2.3 times higher than the white noise of S-D2-D2-D11/2-D1=10-o/Hz-D11/2-D1.3。我们的SQUID microscope system in order to detect Fe-D22-D2 O-D23-D2 magnetic nanoparticles。一种特殊的排水方式，以在SQUID和样本之间形成距离，如1毫米是开发的。即使在10高斯磁场的情况下，该系统的工作也很好。生物免疫测定是在现有系统下进行的。在现有系统中，作为抗体被标记为Fe-D22-D2 O-D23-D2 nanoparticles。Binding reaction between antigen and its antibody can be detected by measuring the magnetic field from FeイイD22イイD23イエD2nanoparticles。这表明，目前的系统比使用光学标记的传统方法更敏感10次。这是有可能通过比其他因素更大的提高敏感性的。

In this research, we developed high Tc SQUID magnetic-microscope system for biological application. Our results are summarized as follows.1. We developed high performance SQUID utilizing bicrystal junctions with 30-degree misorientation angles. At 77 K, we can routinely obtain the voltage modulation depth ΔV>20μV and the flux noise SィイD2φィエD2ィイD11/2ィエD1<12μφィイD2oィエD2/HzィイD11/2ィエD1 for 100pH-SQUID.2. We significantly reduced the 1/f noise of the direct-coupled magnetometer. In order to avoid the flux trapping in the pickup coil, we develop a pickup coil which consists of 4 parallel loop with narrow line-width and involves the so-called flux dam. With this pickup coil, the flux noise is reduced to SィイD2φィエD2ィイD11/2ィエD1=23μφィイD2oィエD2/HzィイD11/2ィエD1 at f=1 Hz. This values is only 2.3 times higher than the white noise of SィイD2φィエD2ィイD11/2ィエD1=10μφo/HzィイD11/2ィエD1.3. We developed a SQUID microscope system in order to detect FeィイD22ィエD2OィイD23ィエD2 magnetic nanoparticles. A special Dewar to make a distance between the SQUID and sample as small as 1 mm is developed. The system works well even when the magnetic field of 10 Gauss is applied in parallel to the SQUID.4. Biological immunoassay is performed with the present system. In the present system, as antibody is labeled with FeィイD22ィエD2OィイD23ィエD2 nanoparticles. Binding reaction between antigen and its antibody can be detected by measuring the magnetic field from FeィイD22ィエD2OィイD23ィエD2 nanoparticles. It is shown that the present system is 10 times more sensitive than the conventional method using an optical marker. It will be possible to improve the sensitivity by more than factor 10.