Precision impedance analyser for nano and mesoscale materials characterization

马尼托巴大学材料物理研究的三个不同领域需要高精度的阻抗分析仪来测量介观材料的阻抗。这些研究领域包括：1)表征小体积磁性纳米颗粒胶体分散体（即铁磁流体）的复杂、频率相关的磁化率。这些测量将探测纳米颗粒的旋转布朗运动，并为不同纳米颗粒涂层（例如药物覆盖的纳米颗粒）的效果提供一个窗口。实验将提供涂层厚度的测量，以及不同的涂层如何影响纳米颗粒在流体中的运动（与磁性纳米颗粒的医学应用发展有关）。2)表征最近发现的巨磁阻抗（GMI）现象的磁性材料的电阻抗。从纯粹和应用的角度来看，这些材料都很有趣——后者涉及产品识别码和假冒保护。3)高衰减食品系统中超声频率剪切模量测量。在这些材料中，脉冲传输技术通常失败，但是当加载样品时，超声波剪切波换能器的阻抗变化的测量为确定剪切模量提供了一种灵敏的方法。还需要通过测量阻抗随位置和时间的变化来研究食品泡沫的排水。这些研究将使生产过程中食品质量评估的新技术成为可能（例如，更好的切片面包）。

A high precision impedance analyzer is needed to measure the impedance of mesoscopic materials in three distinct areas of Materials Physics research at the University of Manitoba.  These research areas are: 1)  Characterizing the complex, frequency-dependent susceptibility of small volumes of colloidal dispersions of magnetic nanoparticles (i.e., ferrofluids).  These measurements will probe the rotational Brownian motion of nanoparticles, and provide a window into the effects of different nanoparticle coatings (e.g. a drug-covered nanoparticle).  Experiments will provide a measure of the thickness of the coating, and how different coatings affect the motion of nanoparticles through a fluid (relevant to the development of medical applications with magnetic nanoparticles). 2)  Characterizing the electric impedance of magnetic materials that exhibit the recently discovered phenomenon of giant magnetoimpedance (GMI).  These materials are interesting from a pure and an applied viewpoint -- the latter involving product identification codes and counterfeit protection. 3) Shear modulus measurements at ultrasonic frequencies in highly attenuating food systems. In these materials, pulsed transmission techniques typically fail but measurements of the impedance variation of ultrasonic shear wave transducers when loaded with the sample provide a sensitive method for determining the shear modulus.  It is also needed to study drainage of food foams by measuring the variation of impedance with position and time.  These studies will enable new techniques for food quality assesment during production (e.g., a better loaf of sliced bread).