Diamond quantum sensors in microfluidics technology
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2023-09-01 |
| Journal | Biomicrofluidics |
| Authors | Masazumi Fujiwara |
| Institutions | Okayama University |
| Citations | 4 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis Perspective details the integration of diamond Nitrogen Vacancy (NV) quantum sensors with microfluidic technology, enabling ultrasensitive, multimodal analysis of minute sample volumes.
- Core Value Proposition: Diamond quantum sensors provide high sensitivity and multimodal measurement capabilities (magnetic field, electric field, temperature, pH) within the constrained, micrometer-scale dimensions of microfluidic channels.
- Integration Methods: Sensors are implemented either as NV layers near the surface of bulk diamond chips bonded to PDMS microfluidics, or as functionalized nanodiamonds (NDs) introduced directly into the fluid flow.
- ODMR Optimization: Optically Detected Magnetic Resonance (ODMR) is optimized using miniaturized components, including a notch-shaped coplanar microwave waveguide (CPW) antenna designed for on-chip detection.
- Microwave Performance: The 50-Ω CPW architecture ensures uniform microwave excitation across the detection area and exhibits gigahertz broadband characteristics with a reflection loss of less than 10%.
- High-Resolution Sensing: The integrated platform has successfully demonstrated two-dimensional nuclear magnetic resonance (NMR) spectroscopy with an exceptionally small detection volume of approximately 40 pL.
- Future Development: Efforts are underway to fabricate integrated photonic waveguides within bulk diamond using laser writing to enhance the efficiency of optical excitation and fluorescence collection, overcoming challenges posed by diamondâs high refractive index (n = 2.4).
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| NV Center Fluorescence Range | 630-800 | nm | Deep-red emission upon green excitation. |
| NV Center Excitation Wavelength | 532 | nm | Standard green optical excitation source. |
| Zero-Field Splitting (D) | ~ 2.87 | GHz | Typical frequency for the ms = 0 â ±1 transition in the NV ground state. |
| NMR Detection Volume | ~ 40 | pL | Volume used for two-dimensional nuclear magnetic resonance (NMR) spectroscopy. |
| Microwave Antenna Type | Notch-shaped CPW | N/A | Coplanar Waveguide designed for on-chip ODMR detection. |
| CPW Notch Area Size | 1.5 x 2.0 | mm2 | Area designed for uniform microwave excitation and sample placement. |
| Microwave Reflection Loss | less than 10 | % | Performance metric for the 50-Ω CPW antenna. |
| Diamond Refractive Index (n) | 2.4 | N/A | High index compared to water (n=1.33) or air (n=1.0), challenging optical interfacing. |
| Microfluidic Channel Dimensions (Example) | 2000 x 100 x 80 | ”m | Example dimensions of a straight channel used in integrated platforms (Fig. 2e). |
| Nanodiamond (ND) Size | Nano-scale | N/A | Used for labeling analytes and introduced into the fluid flow. |
Key Methodologies
Section titled âKey Methodologiesâ- Sensor Integration: NV quantum sensors are integrated into microfluidics using two primary methods:
- Bulk Chip Integration: Bulk diamond chips containing NV ensembles near the surface are bonded with polydimethylsiloxane (PDMS) microfluidic systems.
- Nanodiamond (ND) Labeling: Antibody-functionalized NDs are introduced directly into the sample fluid, which is then fed into the microfluidic channel for ODMR detection.
- Microwave Excitation Architecture: ODMR requires efficient microwave delivery. This is achieved using computationally designed, notch-shaped 50-Ω coplanar microwave waveguide (CPW) antennas fabricated on glass plates, ensuring uniform magnetic field intensity across the detection area.
- Optical Interfacing: Fluorescence collection is typically performed using a microscope objective. To improve efficiency, especially given diamondâs high refractive index (n=2.4), research focuses on fabricating internal optical waveguides within the bulk diamond chip.
- Waveguide Fabrication: Photonic waveguides and NV centers are generated simultaneously within bulk diamond using femtosecond laser writing combined with subsequent annealing processes.
- Multimodal Sensing: The platform exploits the sensitivity of NV spin resonance frequencies and relaxation times to measure multiple parameters simultaneously, including magnetic field, electric field, temperature, pH, and the presence of radical molecules.
- High-Resolution NMR: Integration includes a spin-prepolarization magnet to enhance sensitivity, enabling two-dimensional nuclear magnetic resonance (NMR) spectroscopy on extremely small (picoliter) sample volumes.
Commercial Applications
Section titled âCommercial ApplicationsâThe integration of diamond quantum sensors with microfluidics provides a powerful toolbox for applications requiring high sensitivity and low sample volume.
- Clinical Diagnostics (Lab-on-a-Chip):
- Development of highly sensitive lateral flow assay test kits (e.g., for HIV-1 RNA detection) achieving zepto-molar sensitivity.
- Rapid, low-volume detection and quantification of biomarkers (e.g., ferritin, gadolinium spin labels) in biological fluids.
- Pharmaceutical and Chemical Analysis:
- Precise quantification and analysis of small analyte volumes, facilitating drug screening and chemical reaction monitoring.
- Enhancing NMR sensitivity for 13C-labeled molecules using diamond nanostructures (e.g., MOF mesopores) for advanced chemical characterization.
- Biological and Cellular Assays:
- Monitoring cellular metabolic activities and oxidative stress responses using ND biosensors.
- Real-time, non-toxic measurement of temperature and magnetic fields within living cells and small organisms (e.g., nematode worms).
- Organ-on-Chip Technology:
- Implementing small, multimodal sensors to mimic and monitor physiological conditions (temperature, pH) within miniature biological tissues engineered inside microfluidic channels.
- Advanced Quantum Metrology:
- Realization of fully integrated, all-in-one microfluidic diamond quantum sensors for high-resolution microscale NV-NMR and multiplexed sensing of magnetic field and temperature.
View Original Abstract
Diamond quantum sensing is an emerging technology for probing multiple physico-chemical parameters in the nano- to micro-scale dimensions within diverse chemical and biological contexts. Integrating these sensors into microfluidic devices enables the precise quantification and analysis of small sample volumes in microscale channels. In this Perspective, we present recent advancements in the integration of diamond quantum sensors with microfluidic devices and explore their prospects with a focus on forthcoming technological developments.
Tech Support
Section titled âTech SupportâOriginal Source
Section titled âOriginal SourceâReferences
Section titled âReferencesâ- 2014 - DNA bioassay-on-chip using SERS detection for dengue diagnosis [Crossref]
- 2022 - Microfluidic technologies and devices for lipid nanoparticle-based RNA delivery [Crossref]
- 2018 - Recent advances in microfluidic technologies for cell-to-cell interaction studies [Crossref]
- 2008 - Purification of nucleic acids in microfluidic devices [Crossref]
- 2019 - Micro- and nanopillar chips for continuous separation of extracellular vesicles [Crossref]
- 2022 - A guide to the organ-on-a-chip [Crossref]
- 2021 - Facilitating implementation of organs-on-chips by open platform technology [Crossref]
- 2009 - A microwave interferometric system for simultaneous actuation and detection of single biological cells [Crossref]
- 2013 - Highly sensitive detection of physiological spins in a microfluidic device [Crossref]
- 2016 - Applications of molecularly imprinted polymer nanoparticles and their advances toward industrial use: A review [Crossref]