Detection of biological signals from a live mammalian muscle using an early stage diamond quantum sensor

At a Glance

Metadata	Details
Publication Date	2021-01-28
Journal	Scientific Reports
Authors	James L. Webb, Luca Troise, Nikolaj Winther Hansen, Christoffer Olsson, Adam M. Wojciechowski
Institutions	Sorbonne Université, Laboratoire des Sciences des Procédés et des Matériaux
Citations	62
Analysis	Full AI Review Included

Technical Documentation & Analysis: Diamond Quantum Sensing for Biosignals

Executive Summary

This research demonstrates a critical advancement in non-invasive biosensing by successfully detecting magnetic fields generated by action potentials in live mammalian muscle using a diamond quantum sensor.

Core Achievement: First demonstration of magnetic sensing of biological signals from live mammalian tissue (mouse muscle) using Nitrogen Vacancy (NV) centers in Single Crystal Diamond (SCD).
Sensitivity & Environment: Achieved a magnetic field sensitivity of 50 pT/√Hz, operating successfully in an ordinary, unshielded laboratory environment, bypassing the need for bulky, cryogenic Superconducting Quantum Interference Devices (SQUIDs).
Material Requirements: The sensor utilized a high-quality [100] SCD substrate with a 20 µm thick, high-density NV layer, highlighting the necessity of precision MPCVD growth control.
Methodology: Employed Optically Detected Magnetic Resonance (ODMR) magnetometry combined with advanced digital signal processing (adaptive notch filtering) to isolate the weak biological signal from significant ambient magnetic noise (50 Hz and 150 Hz harmonics).
Future Outlook: This work serves as a crucial proof-of-concept step toward the ultimate goal of microscopic magnetic imaging of neural activity in biological samples, requiring high spatial resolution (< 10 µm) and high-quality SCD materials.
6CCVD Value Proposition: 6CCVD is uniquely positioned to supply the custom, high-purity SCD wafers and specialized epitaxial layers required to scale and optimize this quantum biosensing technology.

Technical Specifications

The following parameters define the material and performance characteristics achieved in the study:

Parameter	Value	Unit	Context
Diamond Material Type	Single Crystal Diamond (SCD)	N/A	Electronic-grade, [100] oriented
SCD Substrate Dimensions	2 x 2 x 0.5	mm³	Used for sensor fabrication
NV Layer Thickness	20	µm	Grown by Chemical Vapor Deposition (CVD)
Nitrogen Doping (Gas Phase)	5	ppm	Optimized for N-14 incorporation
Proton Irradiation Energy	2.25	MeV	Used for NV creation
Proton Fluence	3 x 10¹⁵	protons/cm²	Post-growth treatment
Annealing Temperature	800	°C	Post-irradiation treatment
NV^- Density Range	0.1 - 1	ppm	Resulting defect concentration
Magnetic Field Sensitivity (Noise Floor)	50	pT/√Hz	Measured in unshielded environment
Estimated Shot Noise Limit	8	pT/√Hz	Theoretical sensitivity limit
ODMR Linewidth	1	MHz	Key metric for sensor quality
DC Bias Magnetic Field (B_DC)	~1.5	mT	Applied by rare-earth magnets
Magnetic Measurement Bandwidth	4.8	kHz	Defined by 30 µs lock-in time constant
Biological Signal Strength (Maximum)	~250	pT	Filtered magnetic readout

Key Methodologies

The experiment relied on precise material engineering and advanced quantum sensing techniques:

Material Growth: A 20 µm thick nitrogen-doped layer was grown via MPCVD onto an electronic-grade [100] SCD substrate (2 x 2 x 0.5 mm³), with nitrogen content optimized to 5 ppm in the gas phase.
NV Creation: The diamond was irradiated with 2.25 MeV protons (3 x 10¹⁵ protons/cm²) and subsequently annealed at 800 °C for 4 hours to generate a high density of NV^- centers (0.1-1 ppm).
ODMR Magnetometry: The sensor was integrated into an inverted microscope setup. Continuous Wave (CW) ODMR was performed using a 532 nm green laser (up to 2 W) for initialization and readout, and a three-frequency microwave drive (2.7-3 GHz) for spin manipulation.
Sample Interface: The live mouse muscle was positioned in a custom chamber, separated from the NV layer by a 16 µm aluminum foil (heatsink) and 50 µm Kapton tape (insulator) to ensure high proximity while mitigating laser heating.
Optogenetic Stimulation: Action potentials were induced in the genetically modified muscle using 470 nm blue LED light pulses (5 ms duration).
Signal Recovery: Raw magnetic data, dominated by low-frequency drift and 50/150 Hz mains noise (±1 µT range), was processed using digital bandpass filtering (20 Hz to 1.5 kHz) and adaptive windowed notch filtering to achieve a measurable signal-to-noise ratio (SNR).

6CCVD Solutions & Capabilities

6CCVD provides the specialized MPCVD diamond materials and processing services necessary to replicate and advance this cutting-edge quantum biosensing research.

Research Requirement	6CCVD Solution & Capability	Technical Advantage for Biosensing
High-Purity SCD Substrates	Optical Grade Single Crystal Diamond (SCD)	Provides low-strain, high-transmission material essential for high-power laser delivery and fluorescence collection in ODMR setups.
Custom NV Layer Growth	Precision Epitaxial SCD Layers (0.1 µm - 500 µm)	We offer highly controlled CVD growth to deposit NV-rich layers of exact thickness (e.g., 20 µm) and tailored nitrogen doping (N-14 or N-15) to maximize NV^- yield and sensitivity.
Large Area Sensors	PCD Wafers up to 125 mm Diameter	While this study used a small SCD piece, 6CCVD can supply large-area Polycrystalline Diamond (PCD) plates (up to 125 mm) for scaling up wide-field magnetic imaging or developing multi-sensor arrays.
Sensor Integration & Dicing	Custom Dimensions and Laser Cutting	We provide precision laser cutting and dicing services to fabricate diamond plates to specific dimensions (e.g., 2 x 2 mm) required for integration into microfluidic chambers and inverted microscope stages.
Surface Preparation	Ultra-Low Roughness Polishing (Ra < 1 nm)	Critical for maximizing the proximity of the sensor to the biological sample, our SCD polishing achieves Ra < 1 nm, minimizing signal decay and improving spatial resolution (< 10 µm goal).
Integrated Contacts/Heatsinks	In-House Custom Metalization	We offer internal metalization services (Au, Pt, Pd, Ti, W, Cu) to deposit custom electrode patterns, thermal management layers (like the aluminum heatsink used in the study), or bonding pads directly onto the diamond surface.

Applicable Materials: To replicate or extend this research, 6CCVD recommends Optical Grade Single Crystal Diamond (SCD) with a precisely controlled Nitrogen-14 doped epitaxial layer (thickness 10 µm - 50 µm) optimized for high NV^- concentration and subsequent high-contrast ODMR.
Customization Potential: The paper utilized unique dimensions (2 x 2 mm) and required specific thermal/electrical interfaces. 6CCVD offers custom laser cutting services and advanced metalization (e.g., Ti/Pt/Au stacks) to integrate the diamond sensor seamlessly into complex microfluidic or microscopy setups.
Engineering Support: 6CCVD’s in-house PhD team specializes in quantum material science and can assist researchers with optimizing material selection, NV creation protocols, and surface preparation for similar Non-Invasive Biosensing and Microscopic Magnetic Imaging projects.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

Tech Support

Original Source

DOI: https://doi.org/10.1038/s41598-021-81828-x