Wideband radio-frequency device for measurements of dielectric properties of small volumes of liquids

A wideband differential detector for high-sensitivity rf and microwave dielectric spectroscopy of liquids is described. The device is unique in that it has very high wideband sensitivity and requires extremely small (nanoliter range) volumes of the liquid. In addition, the device has good linearity and can be used for quantitative extraction of the frequency-dependent dielectric function ε(ω) of extremely small volumes of liquids. Using this device, quantitative measurements of the dielectric function at frequencies from 50 MHz to 1.6 GHz are demonstrated for 200 nL volume samples of liquids. The detector may be used for wideband rf/microwave spectroscopic analysis of chemical and biological samples. (rapid communication)