Novel Fabrication Process for Integration of Microwave Sensors in Microfluidic Channels

Abstract

This paper presents a novel fabrication process that allows integration of polydimethylsiloxane (PDMS)-based microfluidic channels and metal electrodes on a wafer with a micrometer-range alignment accuracy. This high level of alignment accuracy enables integration of microwave and microfluidic technologies, and furthermore accurate microwave dielectric characterization of biological liquids and chemical compounds on a nanoliter scale. The microfluidic interface between the pump feed lines and the fluidic channels was obtained using magnets fluidic connection. The tube-channel interference and the fluidic channel-wafer adhesion was evaluated, and up to a pressure of 700 mBar no leakage was observed. The developed manufacturing process was tested on a design of a microwave-microfluidic capacitive sensor. An interdigital capacitor (IDC) and a microfluidic channel were manufactured with an alignment accuracy of 2.5 µm. The manufactured IDC sensor was used to demonstrate microwave dielectric sensing on deionized water and saline solutions with concentrations of 0.1, 0.5, 1, and 2.5 M. Author Contributions: Conceptualization, J.B. and T.M.; methodology, J.B., L.B., and D.K. ; validation, J.B. and T.M.; data curation, J.B.; writing-original draft preparation, J.B. and T.M.; writing-review and editing, J.B., T.M., L.B., D.K., I.O., R.P., and B.N.; visualization, T.M.; supervision, I.O. and B.N.; and funding acquisition, T.M., I.O., R.P., and B.N. All authors have read and agreed to the published version of the manuscript.

Microfluidic Modules Integrated with Microwave Components—Overview of Applications from the Perspective of Different Manufacturing Technologies

“…Then, bonding to a glass/Si substrate containing a microwave microstrip circuit using oxygen plasma is carried out [ 52 ]. However, the possibility of omitting the plasma-bonding in the fabrication process has recently been reported, which is described well in [ 54 ].…”

Numerical modeling of two microwave sensors for biomedical applications

“…The devices are fabricated in the cleanroom lab of Leuven NanoCentre with the fabrication process described as follows. 44 Due to its transparency, isotropic permittivity, and low loss property, a 4-in. fused silica (quartz) (ε r = 3.78, tanδ = 0.0001 at 10 GHz and 25 ∘ C) wafer, is herein used.…”

On the Wireless Microwave Sensing of Bacterial Membrane Potential in Microfluidic-Actuated Platforms

“…Particularly, electromagnetic wave (EM-w) biosensors are attracting a lot of attention due to multiple benefits, such as being minimally invasive and cost effective [ 5 , 6 , 7 ]. For instance, recent advances in microwave sensing [ 8 , 9 , 10 ] enable the exploration of new frequency band windows for conducting novel research on membrane interactions. In particular, microwave frequencies allow to efficiently monitor biological elements and properties inside the human body, with considerable penetration distances (in the order of ) and resolutions (in the order of ) [ 11 ].…”