A wireless bio-sensing microfluidic chip based on resonating ‘μ-divers’

Abstract

A magneto-elastic resonant 'micro-diver' system (MER-μDS) is proposed and developed for rapid liquid-phase detection of pathogens in a wireless way. The magneto-elastic micro-resonator (i.e., the μ-diver) is placed in the micro-chamber of the MER-μDS that is connected to the inlet/outlet for flow of the liquid analyte and a closed-loop micro-channel. After specific attachment of the analyte onto the μ-diver, the μ-diver is conveyed by the flow into the detection segment of the channel, around which a metal micro-coil is wound for both excitation resonance of the μ-diver and reading of its resonance frequency signal. After the pre-functionalized μ-diver captures the analyte and, then, is driven into the detection channel segment, the added mass induced resonant frequency shift can be wirelessly sensed by the coil. The micro-system features rapid and repeatable liquid-phase bio-sensing and the wireless signal readout scheme is favorable to real-time pathogen detection in liquid food, e.g., milk or juice, for food safety applications. An equivalent circuit model is established for design of the magneto-elastic μ-diver. After a bar-shaped μ-diver with length-extensional bulk-resonance mode is optimally designed and micro-fabricated, the MER-μDS is formed by micro-machining/assembling techniques. By placing a biotin-immobilized μ-diver into the wireless micro-sensing system, avidin-attached magnetic beads are detected to calibrate the mass sensitivity as 0.061 Hz pg(-1), which well confirms the modeling result. By using the antibody-immobilized μ-diver, PBS solution with an E. coli concentration of 10(2)-10(8) CFU mL(-1) is detected, resulting in a corresponding wireless f0-shift sensing signal of about 300-2300 Hz and a limit of detection of 10(2) CFU mL(-1). Food safety application potential of the MER-μDS technique is proven by detection of E. coli added to orange and apple juices (E. coli concentration: 10(4)-10(8) CFU mL(-1)).

Core-Shell Magnetic Nanoparticles for Highly Sensitive Magnetoelastic Immunosensor

“…The length to width ratio is needed to be greater than five for a good magnetoelastic response of the material, the latter being further improved for ratios greater than fourteen [ 36 ]. In our case we chose a length to width ratio of six because, as the length and mass of the sensor increases, the mass sensitivity decreases [ 37 ]. When the testing temperature, humidity and other environmental parameters are constant, the resonance frequency change of the magnetoelastic sensor depends only on the mass change on its surface.…”

“…When the testing temperature, humidity and other environmental parameters are constant, the resonance frequency change of the magnetoelastic sensor depends only on the mass change on its surface. In the approximation of small mass loading (Δ m « M ME ) uniformly distributed on the ribbon surface, the shift in resonance frequency in low viscosity liquids is given by equation: where is the initial resonance frequency in liquid, its variation due to the detection of antigens of mass Δ m and is the initial mass of the ribbon [ 37 ]; thus, the sensitivity of the sensor is: …”

“…where f 0 is the initial resonance frequency in liquid, ∆ f 0 its variation due to the detection of antigens of mass ∆m and M ME is the initial mass of the ribbon [37]; thus, the sensitivity of the sensor is:…”

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Can a Water Smart Grid Help Society Achieve the Sustainable Development Goal of Water as a Human Right?

“…In addition, technology does not exist that can individually identify most bacteria.The latter is not as relevant, since our methods for disinfection are targeted to eliminate the most recalcitrant bacteria, though determining viability of Technology to measure "safe." Compact methods for detecting bacterial and chemical contaminants are being developed[52,53]. screened microbes would be.…”