title: A palm-size μNMR relaxometer using a digital microfluidic device and a semiconductor transceiver for chemical/biological diagnosis.
abstract: Herein, we describe a micro-nuclear magnetic resonance (μNMR) relaxometer miniaturized to palm-size and electronically automated for multi-step and multi-sample chemical/biological diagnosis. The co-integration of microfluidic and microelectronic technologies enables an association between the droplet managements and μNMR assays inside a portable sub-Tesla magnet (1.2 kg, 0.46 Tesla). Targets in unprocessed biological samples, captured by specific probe-decorated magnetic nanoparticles (NPs), can be sequentially quantified by their spin-spin relaxation time (T2) via multiplexed μNMR screening. Distinct droplet samples are operated by a digital microfluidic device that electronically manages the electrowetting-on-dielectric effects over an electrode array. Each electrode (3.5 × 3.5 mm(2)) is scanned with capacitive sensing to locate the distinct droplet samples in real time. A cross-domain-optimized butterfly-coil-input semiconductor transceiver transduces between magnetic and electrical signals to/from a sub-10 μL droplet sample for high-sensitivity μNMR screening. A temperature logger senses the ambient temperature (0 to 40 °C) and a backend processor calibrates the working frequency for the transmitter to precisely excite the protons. In our experiments, the μNMR relaxometer quantifies avidin using biotinylated Iron NPs (Φ: 30 nm, [Fe]: 0.5 mM) with a sensitivity of 0.2 μM. Auto-handling and identification of two targets (avidin and water) are demonstrated and completed within 2.2 min. This μNMR relaxometer holds promise for combinatorial chemical/biological diagnostic protocols using closed-loop electronic automation.
authors.affiliation: State-Key Laboratory of Analog and Mixed-Signal VLSI, University of Macau, China. pimak@umac.mo.
authors.forename: Ka-Meng
authors.initials: KM
authors.lastname: Lei
authors.forename: Pui-In
authors.initials: PI
authors.lastname: Mak
authors.forename: Man-Kay
authors.initials: MK
authors.lastname: Law
authors.forename: Rui P
authors.initials: RP
authors.lastname: Martins
mesh_terms: D001360:Avidin / Q000032:analysis*; D019921:Biotinylation; D058874:Electrowetting; D007501:Iron / Q000737:chemistry*; D056656:Lab-On-A-Chip Devices; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation*; D053768:Metal Nanoparticles / Q000737:chemistry*; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation*; D012666:Semiconductors
chemical_list: D001360:Avidin; D007501:Iron