Using Microwave Sensors To Detect The Biochemical Liquid

With the development of science and technology,in the field of chemistry and biology,we often need to detect the biochemical liquid.At the same time,the microwave sensor with its excellent performance has very extensive application in many fields,so we can use microwave sensors to detect the concentration or the cell density of biochemical liquid in theory.Although there are a variety of methods to detect chemical and biological liquid,but most of them have some deficiencies,and can not meet the needs of all aspects.Microwave method can not only overcome the shortcomings of these methods,but also has its own unique advantages,namely non-contact detection,continuous real-time monitoring and wide detection object.We chose three kinds of biochemical liquid as the detection objects.They are sodium chloride solution,glucose solution and E.coli suspension,representing electrolyte solution,non-electrolytic solution and cell suspension.The relative dielectric constant of these three kinds of biochemical liquid will change with the concentration or the cell density,which also is the basis of microwave sensors can detect biochemical liquid.We used the two microwave sensors,which are coaxial line sensor and resonator sensor.Although they both depend on the relative dielectric constant change of biochemical liquid,but their measuring principle are not exactly the same.The electromagnetic parameter of coaxial line sensor measures is the S₁₁parameter,and resonator sensor measures resonance frequency offset.In the detecting experiments of these three kinds of biochemical liquid,the concentration of sodium chloride and dextrose solution can realize quantitative detection,and the cell density of E.coli suspension can only achieve qualitative detection.The key to the quantitative detection of the concentration is to establish the measurement relationship between the concentration and the electromagnetic parameters measured by microwave sensors.In the detecting experiments of coaxial line sensor,we established the measurement relationship between the concentration and S₁₁ parameter.After getting the complete measurement relationship,we can use the S₁₁ parameter to calculate the concentration directly,so as to achieve the purpose of quantitative detection of the concentration.In the detecting experiments of resonator sensor,we established the measurement relationship between the concentration and resonance frequency offset,and can also achieve the purpose of quantitative detection of the concentration.We can not grasp the relationship between cell density of E.coli suspension and the relative dielectric constant accurately,because E.coli suspension is not a homogeneous medium.Therefore,in the detecting experiments of two microwave sensors,the cell density of E.coli suspension can only achieve qualitative detection.In a word,we use microwave sensors to convert the concentration or the cell density of biochemical liquid from non-electric parameters to the electromagnetic parameters associated with microwave,such as S₁₁ parameter or resonance frequency,so that achieve the purpose of quantitative or qualitative detection.