In Situ Studies of Stress Environment in Amorphous Solids Using Negatively Charged Nitrogen Vacancy (NV–) Centers in Nanodiamond
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2020-12-08 |
| Journal | ACS Applied Polymer Materials |
| Authors | Kin On Ho, Man Yin Leung, Yiu Yung Pang, King Cho Wong, Ping Him Ng |
| Institutions | Chinese University of Hong Kong, Chinese University of Hong Kong, Shenzhen |
| Citations | 8 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: In-Situ Stress Sensing in Amorphous Solids using NV Centers
Section titled “Technical Documentation & Analysis: In-Situ Stress Sensing in Amorphous Solids using NV Centers”Executive Summary
Section titled “Executive Summary”This research demonstrates a breakthrough protocol utilizing negatively charged Nitrogen Vacancy (NV-) centers in nanodiamond (ND) as versatile quantum sensors for in situ measurement of local stress and strain in amorphous solids during chemical processes.
- Quantum Sensing Breakthrough: NV- centers enable microscopic, spatially resolved mapping of local shear stress and pressure during the curing of polymers (PDMS and Cyanoacrylate).
- High Local Stress Detection: The methodology revealed local shear stresses significantly higher (3.3x to 5.8x) than the bulk ultimate tensile strength (UTS) of the materials (e.g., 148 MPa detected in Cyanoacrylate).
- Nanoscale Resolution: By comparing 1 µm and 100 nm ND sensors, the study confirmed that smaller sensors provide enhanced sensitivity and spatial resolution, detecting residual strain variations at later stages of polymerization.
- Decoupling Stress Components: The protocol successfully isolated shear strain (measured via transverse Zero-Field Splitting, $E$) from hydrostatic pressure (measured via longitudinal ZFS, $D$).
- Critical Applications: This technique is vital for optimizing manufacturing processes, refining adhesive performance, and advancing research in soft condensed matter physics and biomaterials.
- 6CCVD Value Proposition: 6CCVD provides the high-purity Single Crystal Diamond (SCD) substrates necessary for creating next-generation, high-coherence NV- quantum sensors, offering superior material control compared to commercial nanodiamond powders.
Technical Specifications
Section titled “Technical Specifications”| Parameter | Value | Unit | Context |
|---|---|---|---|
| Sensor Type | NV- Center | N/A | Negatively Charged Nitrogen Vacancy in Nanodiamond |
| Sensor Sizes Tested | 1 µm and 100 nm | µm/nm | Used to determine size-dependent spatial resolution |
| Nitrogen Concentration | 3 | ppm | Concentration used in ND sensors |
| Longitudinal ZFS ($D$) (Ambient) | ≈ 2.87 | GHz | Zero-Field Splitting at room temperature |
| Gyromagnetic Ratio ($\gamma$) | 2.803 | MHz/G | Used for Zeeman splitting calculations |
| Temperature Sensitivity ($dD/dT$) | -74 | kHz/K | Used for correcting temperature artifacts |
| Stress Susceptibility (Isotropic Approx.) | 1.75 | MHz/GPa | Assumed isotropic response ($a=b=c$) for stress conversion |
| PDMS Curing Time ($2\tau$) | < 24 | hours | Time to reach strain stabilization |
| PDMS Local Shear Stress (Calculated) | 29.6 | MPa | Based on average $\Delta E = 0.1$ MHz |
| Cyanoacrylate Local Shear Stress (100 nm ND) | 148 | MPa | Highest stress detected, based on average $\Delta E = 0.5$ MHz |
| Measurement Scale | Sub-micron | N/A | Local properties probed at the position of individual NDs |
Key Methodologies
Section titled “Key Methodologies”The experiment employed Optically Detected Magnetic Resonance (ODMR) spectroscopy using a home-built confocal microscope setup to monitor the energy level shifts of NV- centers embedded in curing polymers.
- Sensor Preparation: Nanodiamond (ND) solutions (1 µm and 100 nm, 3 ppm N) were prepared via ultrasound treatment to remove clusters.
- Substrate Setup: Plasma-cleaned glass slides were drop-casted with ND solution and mounted onto a Printed Circuit Board (PCB) containing a 50 µm microwave (MW) transmission wire.
- Sample Application: Poly dimethylsiloxane (PDMS, SYLGARD 184, 10:1 ratio) or Cyanoacrylate (AA glue) was added onto the glass slide, ensuring NDs were located at the interface.
- ODMR Measurement: A 520 nm green laser was used for NV- initialization and readout. The MW signal manipulated the electron spin states.
- Data Acquisition: Temporal variations of the longitudinal ZFS ($D$) and transverse ZFS ($E$) were measured over several days (up to 60+ hours) to track pressure and strain changes in situ.
- Environmental Control: Environment temperature was continuously monitored to eliminate spectral artifacts caused by temperature fluctuations, isolating the effects of pressure and local heating.
- Stress Calculation: Changes in $E$ ($\Delta E$) were converted to local shear stress using an isotropic stress susceptibility approximation ($1.75$ MHz/GPa).
6CCVD Solutions & Capabilities
Section titled “6CCVD Solutions & Capabilities”This research highlights the critical need for high-quality, highly controlled diamond material to serve as robust quantum sensors. 6CCVD is uniquely positioned to supply the foundational materials required to replicate and advance this cutting-edge quantum sensing technology.
Applicable Materials
Section titled “Applicable Materials”The success of NV- sensing relies on precise control over nitrogen doping and crystal quality. 6CCVD offers superior MPCVD Single Crystal Diamond (SCD) materials ideal for NV center creation:
- High-Purity SCD Wafers: Our SCD material provides the lowest defect density and highest purity necessary for creating NV centers with long coherence times ($T_{2}$), crucial for maximizing sensor sensitivity.
- Controlled Nitrogen Doping: We offer SCD with precise, controlled nitrogen concentrations (including ultra-low N for high-coherence applications, or specific doping levels for high-density sensing arrays), surpassing the variability often found in commercial ND powders.
- Custom Substrates: While the paper used ND powder, future integrated quantum sensors require high-quality SCD plates. 6CCVD supplies SCD plates up to 500 µm thick, which can be subsequently processed (e.g., ion implantation, annealing, milling) to create high-performance NV sensors or integrated diamond micro-electromechanical systems (MEMS).
Customization Potential
Section titled “Customization Potential”To move beyond proof-of-principle measurements and integrate NV sensors into industrial or complex research environments, custom fabrication is essential.
| Research Requirement | 6CCVD Custom Capability | Technical Advantage |
|---|---|---|
| Sensor Integration | Custom SCD Plates/Wafers (up to 125mm) | Provides large, uniform starting material for high-volume sensor fabrication. |
| Signal Transmission | Custom Metalization (Au, Pt, Ti, W, Cu) | Enables integration of MW transmission lines (like the 50 µm wire used in the paper) directly onto or adjacent to the diamond sensor substrate. |
| Surface Quality | Ultra-low Polishing (Ra < 1 nm for SCD) | Essential for minimizing surface defects that can degrade NV coherence and for ensuring optimal optical coupling in confocal setups. |
| Micro-structuring | Precision Laser Cutting and Etching | Allows for the creation of custom diamond micro-structures (e.g., cantilevers, micro-anvils, or precisely sized ND precursors) for enhanced stress coupling. |
Engineering Support
Section titled “Engineering Support”The paper notes that precise evaluation of the full stress tensor requires a well-controlled external magnetic field and detailed knowledge of the NV axis orientation. 6CCVD’s in-house team of PhD material scientists and quantum engineers can provide expert consultation:
- Material Selection for Quantum Applications: Assistance in selecting the optimal SCD grade, thickness, and nitrogen doping level to maximize NV center density and coherence time for specific quantum sensing projects (e.g., high-pressure physics, magnetic sensing, or local strain mapping).
- Integration Guidance: Support for engineers designing integrated diamond quantum devices, including advice on metal adhesion, surface preparation, and post-growth processing (implantation/annealing) required to activate NV centers.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly. Global shipping (DDU default, DDP available) ensures rapid delivery of high-quality MPCVD diamond worldwide.
View Original Abstract
Amorphous solids, which show characteristic differences from crystals, are common in daily usage. Glasses, gels, and polymers are familiar examples, and polymers are particularly important in terms of their role in construction and crafting. Previous studies have mainly focused on the bulk properties of polymeric products, and the local properties are less discussed. Here, we designed a distinctive protocol using the negatively charged nitrogen vacancy (NV-) center in nanodiamond to study properties inside polymeric products in situ. Choosing the curing of poly(dimethylsiloxane) (PDMS) and the polymerization of cyanoacrylate as subjects of investigation, we measured the time dependence of local pressure and strain in the materials during the chemical processes. From the measurements, we were able to probe the local shear stress inside the two polymeric substances in situ. By regarding the surprisingly large shear stress as the internal tension, we attempted to provide a microscopic explanation for the ultimate tensile strength (UTS) of a bulk solid. Our current methodology is applicable to any kind of transparent amorphous solids with the stress in the order of MPa and to the study of in situ properties in nanoscale. With better apparatus, we expect the limit can be pushed to sub-MPa scale.