Developement of a novel laser-beam-scanning bio-chemical sensing microscope

利用本基金研制了一种新型的化学成像显微镜。化学成像显微镜基于光寻址电位传感器（LAPS）的原理。LAPS器件与电解液接触的敏感表面由沉积在半导体Si衬底上的绝缘Si_3N_4膜制成。将电解液中的二维化学信息映射到Si衬底中耗尽层宽度的变化上。用扫描激光束照射硅衬底背面，以光电流的形式测量了耗尽层电阻抗随位置的变化，并对空间分辨率、灵敏度和测量速度进行了研究，使之达到10 μ m、0.01pH和100象素/秒。该显微镜已被证实具有电解样品中二维生物/化学信息的可视化能力;微生物菌落的pH值分布、特异性分子和氧化还原电位，也可用于快速变化的电位成像，如活性神经元电位。为了证明它对更快过程的适用性，我们测量了Belousov-Zhabotinsky反应中的化学波。化学波的传播被观察为氧化还原电位的变化，无论是在一个固定的点上，或在沿着传播方向的线上。这种测量将有助于氧化还原反应体系中反应扩散和图案形成现象的微观分析。

A novel chemical imaging microscope has been developed with the aid of the present grant. The chemical imaging microscope is based on the principle of the light-addressable potentiometric sensor (LAPS). The sensing surface of a LAPS device in contact with the electrolyte is made of insulating Si _3N_4 film deposited on semiconducting Si substrate. The two-dimensional chemical information in the electrolyte is mapped into the variation of the width of depletion layr in Si substrate. The electrical impedance of the depletion layr is measured as a function of position, in the form of photocurrent induced by scanning-laser-beam that illuminates the rear surface of the Si substrate.The spatial resolution, sensitivity and measurement speed have been investigated and improved to be 10 micron meter, 0.01pH and 100 pixels/sec, respectively.The microscope has been verified to have capability of visualization of two-dimensional bio/chemical information in electrolytic specimens ; distribution of pH of microorganism colonies, specific molecules and redox potential.It could be also used for imaging rapidly changing electrical-potential such as active neuron potential. To demonstrate its applicability to faster processes, we measured the chemical waves in Belousov-Zhabotinsky reaction. Propagation of chemical waves was observed as variation of redox potential either at a fixed point or on a line along the propagating direction. Such measurement would be useful for microscopic analysis of reaction-diffusion and pattern-formation phenomena in redox reaction systems.