Continuous Determination of Glucose Using a Membraneless, Microfluidic Enzymatic Biofuel Cell

In this article, we describe an enzyme-based, membraneless, microfluidic biofuel cell for the continuous determination of glucose using electrochemical power generation as a transducing signal. Enzymes were immobilized on multi-walled carbon nanotube (MWCNT) electrodes placed parallel to the co-laminar flow in a Y-shaped microchannel. The microchannel was produced with polydimethylsiloxane (PDMS) using soft lithography, while the MWCNT electrodes were replicated via a PDMS stencil on indium tin oxide (ITO) glass. Moreover, the electrodes were modified with glucose oxidase and laccase by direct covalent bonding. The device was studied at different MWCNT deposition amounts and electrolyte flow rates to achieve optimum settings. The experimental results demonstrated that glucose could be determined linearly up to a concentration of 4 mM at a sensitivity of 31 mV∙mM−1cm−2.

Continuous Characterization of Permittivity over a Wide Bandwidth Using a Cavity Resonator

We examine a rectangular cavity resonator method to accurately characterize the complex permittivity of dielectric materials over a wide frequency range of 1–5 GHz by exploiting the fundamental mode and higher-order TE_{(1,0,<i>l</i>)} modes. For this purpose, a rectangular waveguide is coupled with a cavity resonator through a large inductive aperture. The permittivity characterization at both even and odd TE_{(1,0,<i>l</i>)} modes enables continuous determination of the permittivity over operating frequencies. The characterization of the permittivity for even TE_{(1,0,<i>l</i>)} modes suffers from potential errors due to the displacement of materials. This paper also proposes a method to compensate for these errors and improve the accuracy in the even modes. The experimental results of the fabricated cavity are presented using different materials (frequency-independent and frequency-dependent). The measured complex permittivity results show a good agreement with the reported results over a wide bandwidth available in the literature.