Development of a microsystem based on a microfluidic network to tune and reconfigure RF circuits

Abstract

This special issue presents devices and the results of a tunable microwave microsystem associating RF circuits and microfluidic components. A channel is buried inside the substrate of a microstrip waveguide. This channel is located beneath a resonant stub. With this configuration a microfluidic passive tunable filter can be fabricated. Dielectric fluids are used to disrupt the electric field in a microstrip structure and thus modify the effective permittivity of the substrate. In this work, a notch filter is realized with an open-ended quarter-wavelength stub placed on top of a hollow SU-8 structure. This structure offers two advantages: channels can easily be fabricated and a reduction of SU8 losses. The filter shows a good performance; the initial cut-off frequency of 25 GHz shifts more than 20% when deionized water is used in fluidic channels. And the shape of RF function is kept throughout the range.

Large frequency tuning of a millimeter-wave antenna using dielectric liquids in integrated micro-channels

“…R03003 and LCP are electrically identical (G/ep = 2.98, Tan61ep = 0.004), so in most area, Greq = Glep. However, in the channels area Greq is strongly modified by the presence of the liquid (G/iq, Tan6liq) and can be estimated by (2) [10]:…”

Microfluidically Tunable Microstrip Filters

“…Instead of using electrical switches, they rely on the use of small volumes of conductive or dielectric fluids, whose flow is controlled by a micropump or external stimuli. A precise and reversible manipulation with the shape or position of fluid droplets enables development of various tunable microwave devices, including phase shifters [11], filters [12]- [16], MEMS [17], [18], and unit cells for frequency-selective surfaces [19] and transmit arrays [20].…”

“…1). The basic idea of this approach was introduced in [12] in the form of a tunable stub resonator backed on to a polymer substrate with integrated microfluidic channels. In [15], a cavity-backed microfluidically switchable filter animated using two different fluids was reported.…”

“…Unlike earlier studies [12], [15], the microfluidic network of the filters reported in this paper is created using plastic tubes placed below a suspended dielectric substrate supporting inverted MS lines oriented along the stubs. The specific orientation of the microfluidic channels and the use of commercially available materials helped us to increase the filter tuning range and simplify its practical implementation.…”

“…The advantages of this approach compared to the cavity-based filter reported in [15] include lower complexity of the microfluidic network, proven reversible performance, faster switching time, and lower IL. Finally, the flexibility of plastic tubing potentially enables their integration into conformal and flexible substrates, which is not the case for the designs reported in [12] and [15]. This makes the proposed approach potentially compatible with emerging applications in the domain of flexible electronics, such as body-worn wireless sensors for medical and robotic applications.…”