| Metadata | Details |
|---|
| Publication Date | 2024-05-08 |
| Journal | Photonics |
| Authors | Zhenxian Fan, Xing Li, Feixiang Wu, Xiaojuan Feng, Jintao Zhang |
| Institutions | Tsinghua University, China Jiliang University |
| Citations | 5 |
| Analysis | Full AI Review Included |
- Core Objective: Optimization of microwave antenna characteristics (Double Open Loop Resonant (DOLR) and Broadband Large-Area (BLA)) to maximize the sensitivity of Nitrogen-Vacancy (NV-) center thermometry in living cell environments.
- Superior Antenna Selection: The DOLR microwave antenna was identified as significantly more suitable for cellular applications due to its high Quality Factor (Q) and superior magnetic field uniformity.
- Thermal Management Achievement: The optimized DOLR antenna achieved a Q value of 40.43, nearly three times higher than the BLA antenna (Q = 9.22), resulting in substantially lower microwave heating effectsâa critical requirement for maintaining cell viability in the narrow 5.5 K temperature tolerance range.
- Frequency and Resonance Matching: Optimization successfully tuned the DOLR center frequency to 2.8744 GHz, precisely matching the NV center zero-field splitting resonance required for accurate ODMR measurement.
- Sensitivity Enhancement: Experimental ODMR results confirmed that the DOLR antenna provides the best ultimate sensitivity and Signal-to-Noise Ratio (SNR) across the tested power range, with optimal performance achieved between -15 dBm and -10 dBm.
- Environmental Modeling: The simulation incorporated complex environmental factors (culture medium, culture dish, glass slide) which caused significant frequency shifts (up to 0.4009 GHz for BLA), demonstrating the necessity of environment-specific antenna optimization.
| Parameter | Value | Unit | Context |
|---|
| Target Measurement Temperature Range | 36 to 42.5 | °C | Optimal range for living cell activity |
| NV Zero Field Splitting (D) Change | ~400 | kHz | Total D variation across the target temperature range |
| D-T Sensitivity (dD/Dt) | ~-74.2 | kHz/K | Sensitivity of NV center splitting energy to temperature |
| Optimized DOLR Center Frequency | 2.8744 | GHz | Optimized for NV resonance in cellular environment |
| Optimized DOLR Bandwidth | 71 | MHz | Optimized value in cellular environment |
| Optimized DOLR Quality Factor (Q) | 40.43 | N/A | Optimized value, indicating low heat loss |
| Optimized DOLR S11 (Return Loss) | -6.8 | dBm | At center frequency |
| Optimized DOLR Magnetic Field Strength | 344.9 | A/m | Optimized value in cellular environment |
| Optimized DOLR Planar Uniformity | 0.98 | N/A | Uniformity (Hmax - Hmin)/Hmid |
| Optimized BLA Quality Factor (Q) | 9.22 | N/A | Optimized value in cellular environment |
| Optimal Microwave Power (DOLR) | -15 to -10 | dBm | Range for best SNR and high Q factor |
| Maximum Tolerable Temp. Rise | 5.5 | K | Maximum temperature difference living cells can adapt to |
| Original BLA Center Frequency (Air) | 2.968 | GHz | Initial design (without media/dish) |
| Original DOLR Center Frequency (Air) | 2.880 | GHz | Initial design (without media/dish) |
- Environmental Modeling: Established computational models for BLA and DOLR antennas incorporating the dielectric and electromagnetic properties of the cellular environment, including the culture dish (dielectric constant Δr = 3.01), glass slide (Δr = 5.42), and culture medium (conductivity Ï = 5400 ± 100 ”S/cm).
- Antenna Parameter Optimization: Employed a univariate control method to systematically adjust structural parameters (e.g., ring radii, coupling gaps, lead width) to minimize the center frequency offset caused by the cellular environment and maximize the Quality Factor (Q) and magnetic field uniformity.
- ODMR System Setup: Utilized a continuous 532 nm laser, modulated by an Acousto-Optic Modulator (AOM), to excite NV centers in flaky diamond samples. Fluorescence was collected through a dichroic mirror and filtered (FELH0600) before detection by a Single Photo Counting Module (SPCM).
- Microwave Signal Generation: Microwave signals were generated using a source (SMIQ 06B), amplified (ZHL-16W-43-S+), and controlled via an RF switch (ZASWA-2-50DRA+) before being fed to the antenna under test.
- Performance Quantification: Experimental ODMR spectra were measured across a microwave power sweep (-25 dBm to -5 dBm). Antenna performance was quantitatively compared using the ratio of line bandwidth to contrast (a proxy for Signal-to-Noise Ratio, SNR) and the calculated Q value (Center Frequency/Bandwidth).
- Nanoscale Quantum Thermometry: High-resolution, non-invasive temperature sensing within biological systems (e.g., single cells, organelles) for fundamental biological research and drug development.
- Biomedical Hyperthermia Monitoring: Real-time monitoring of localized temperature during therapeutic procedures, such as photothermal tumor ablation, ensuring precise thermal dosage control.
- Quantum Sensing Platforms: The optimized antenna design methodology is directly transferable to other NV-diamond based quantum sensors requiring high magnetic field uniformity and low thermal noise, such as magnetometers and electrometers.
- High-Frequency Microelectronics: Design of specialized high-Q microwave resonators and microstrip components for low-power, low-loss applications in sensitive electronic and quantum computing hardware.
- Diamond Material Characterization: Advanced tools for characterizing the spin properties and coherence times of NV centers in synthetic diamond materials under various environmental loads.
View Original Abstract
A typical solid-state quantum sensor can be developed based on negatively charged nitrogen-vacancy (NVâ) centers in diamond. The electron spin state of NVâ can be controlled and read at room temperature. Through optical detection magnetic resonance (ODMR) technology, temperature measurement can be achieved at the nanoscale. The key to ODMR technology is to apply microwave resonance to manipulate the electron spin state of the NVâ. Therefore, the microwave field characteristics formed near the NVâ have a crucial impact on the sensitivity of ODMR measurement. This article mainly focuses on the temperature situation in cellular applications and simulates the influence of structural parameters of double open loop resonant (DOLR) microwave antennas and broadband large-area (BLA) microwave antennas on the microwave fieldâs resonance frequency, quality factor Q, magnetic field strength, uniformity, etc. The parameters are optimized to have sufficient bandwidth, high signal-to-noise ratio, low power loss, and high magnetic field strength in the temperature range of 36 °C to 42.5 °C. Finally, the ODMR spectra are used for effect comparison, and the signal-to-noise ratio and Q values of the ODMR spectra are compared when using different antennas. We have provided an optimization method for the design of microwave antennas and it is concluded that the DOLR microwave antenna is more suitable for living cell temperature measurement in the future.
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