Highly Sensitive Measurement of Bio-Electric Potentials by Boron-Doped Diamond (BDD) Electrodes for Plant Monitoring

At a Glance

Metadata	Details
Publication Date	2015-10-23
Journal	Sensors
Authors	Tsuyoshi Ochiai, Shoko Tago, Mio Hayashi, Akira Fujishima
Institutions	Kanagawa Academy of Science and Technology, Tokyo University of Science
Citations	14
Analysis	Full AI Review Included

Technical Analysis & Product Opportunity: Highly Sensitive Bio-Electric Monitoring via BDD Electrodes

Executive Summary

This analysis details the use of Boron-Doped Diamond (BDD) electrodes for highly sensitive, stable, and long-term monitoring of bioelectric potentials in living plants, identifying BDD as the superior material choice for advanced agro-engineering and physiological research.

Superior Sensitivity: BDD electrodes demonstrated 4-7 times greater sensitivity in detecting bioelectric potential changes in potted plants (Opuntia) compared to standard Pt or Ag plates.
Long-Term Reliability: BDD proved 5-10 times more sensitive than Pt electrodes for continuous, long-term (months) monitoring of ground-planted trees, effectively detecting environmental shifts (temperature, humidity, rainfall).
Enhanced Stability: BDD exhibited dramatically lower Coefficient of Variability (CV: 15.3%), indicating superior reliability and signal stability compared to Ag (CV: 60.1%) and Pt (CV: 103.1%).
Application Potential: The methodology establishes BDD as critical for creating robust, long-duration plant monitoring systems, serving both as a growth health indicator and an early warning system for environmental events (e.g., storms).
BDD Advantage: The high electrochemical sensitivity and stability of BDD surfaces, previously established for in vivo biochemical detection (e.g., dopamine), translate directly to robust detection of ion flow and surface potential changes in live plant tissue.
6CCVD Opportunity: The success relies on high-quality Polycrystalline Boron-Doped Diamond (P-BDD) plates, a core material specialty of 6CCVD, ready for custom sizing and integrated metalization for commercial deployment.

Technical Specifications

The following table summarizes the key performance metrics and hardware specifications derived from the experimental data comparing BDD, Pt, and Ag electrodes.

Parameter	Value	Unit	Context
Electrode Material Tested	Polycrystalline BDD, Pt, Ag	N/A	Plate electrodes used for comparison.
Electrode Dimensions	10 x 10	mm	Uniform size used for all three materials.
BDD Sensitivity Advantage (Potted)	4-7	times	Compared to Ag and Pt plates.
BDD Sensitivity Advantage (Ground-Planted)	5-10	times	Compared to Pt plates over months.
Mean Potential Change (BDD)	0.208	mV	Highest mean signal detected during touch stimulus.
Mean Potential Change (Pt)	0.046	mV	Lowest mean signal detected during touch stimulus.
BDD Coefficient of Variability (CV)	15.3	%	Indicates high signal stability and low noise.
Pt Coefficient of Variability (CV)	103.1	%	Indicates low signal stability/high noise.
Amplifier Gain (Differential)	10,000	N/A	Used for signal amplification prior to digitization.
Low Pass Filter Frequency	10	Hz	Used to reduce noise and instability.
A/D Converter Resolution	24	bits	Required for processing highly sensitive mV-scale signals.
Long-Term Monitoring Duration	Several	months	Achieved successfully using BDD electrodes.

Key Methodologies

The experimental design focused on securing stable, long-term contact between the diamond electrodes and the exposed vascular tissue of the plants, leveraging BDD’s robust electrochemical properties.

Tissue Preparation:
- For potted plants (Opuntia), the epidermis was peeled to expose green phloem tissue (at least 10 mm x 10 mm area).
- For ground-planted trees (e.g., Eurya japonica), crude bark was sliced off at 1 m height to expose a small, flat area of green phloem tissue.
Electrode Assembly:
- Commercially sourced 10 mm x 10 mm BDD, Pt, and Ag plates were attached using conductive carbon tape (Cat. No. 7311) onto standard Ag/AgCl ECG monitoring electrodes (3M™ Red Dot™).
Electrode Placement:
- Pairs of electrodes (BDD, Pt, or Ag) were fixed onto the exposed plant tissue at the same height with a 10 mm gap, secured using plastic tape.
Noise Mitigation (Ground-Planted Trees):
- Electrodes and contact areas on ground-planted trees were wrapped in aluminum foil after securing with plastic tape to prevent rainwater interference and shield against electromagnetic noise.
Signal Processing Chain:
- Bioelectric potentials were collected differentially and passed through a custom amplifier circuit featuring a gain of 10,000 and a 10 Hz low pass filter.
- Analog signals were digitized using a 24-bit A/D converter (Pico Technology ADC-24) for data logging to a PC.

6CCVD Solutions & Capabilities

6CCVD is uniquely positioned to supply the advanced diamond materials required to replicate, scale, and commercialize this highly sensitive plant monitoring technology. Our MPCVD BDD production ensures the high quality and electrochemical stability necessary for robust in vivo sensing applications.

Applicable Materials

To replicate and enhance the stability and sensitivity achieved in this research, the following 6CCVD material is recommended:

Boron-Doped Diamond (BDD): Specifically, Heavy Boron Doped Polycrystalline Diamond (PCD) wafers or plates.
- Advantage: Our BDD material is synthesized for maximum electrochemical activity and stability, offering a wide potential window and high signal-to-noise ratio crucial for low-voltage bio-sensing applications.
- Thickness: 6CCVD can supply BDD electrodes tailored for specific integration needs, ranging from thin films (0.1 µm) up to thick self-standing substrates (500 µm).

Customization Potential

The research utilized basic 10 mm x 10 mm plates. 6CCVD capabilities allow for immediate improvements in integration complexity and long-term robustness.

Customization Service	Technical Benefit to Plant Monitoring
Precise Custom Dimensions & Cutting	Provides plates/wafers up to 125 mm (PCD). We can laser-cut BDD material into precise small form factors (e.g., 10 mm x 10 mm or custom geometries) required for integration into commercial sensor housings or flexible arrays.
Direct Metalization Layers	The paper used conductive carbon tape and Ag/AgCl electrodes, which compromise long-term stability. 6CCVD offers in-house metalization (e.g., Ti/Pt/Au or Ti/W/Au) directly onto the BDD surface. This creates a superior, low-resistance, high-adhesion contact point, critical for reliable data acquisition over several months in harsh environmental conditions.
Micro-Array Fabrication	For scaling research to high-density monitoring, 6CCVD can assist in patterning BDD surfaces to create interdigitated or micro-dot electrode arrays for localized potential mapping.
Substrate Options	While this research used stand-alone plates, 6CCVD can supply BDD grown on insulating substrates (e.g., high purity SCD) if complex electronic integration or specific optical access is required.

Engineering Support

6CCVD’s in-house team of PhD material scientists and technical engineers specializes in optimizing diamond material properties for challenging electrochemical applications.

Support Offered: We provide expert consultation on selecting the optimal boron doping concentration, surface termination (e.g., hydrogen or oxygen), and polishing strategy for sensitive bio-electric potential sensing and agritech monitoring projects.
Stability Optimization: We specifically assist clients in designing robust electrode assemblies that minimize drift and maximize the shelf life and operational lifespan of sensors in outdoor or industrial environments.

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

View Original Abstract

We describe a sensitive plant monitoring system by the detection of the bioelectric potentials in plants with boron-doped diamond (BDD) electrodes. For sensor electrodes, we used commercially available BDD, Ag, and Pt plate electrodes. We tested this approach on a hybrid species in the genus Opuntia (potted) and three different trees (ground-planted) at different places in Japan. For the Opuntia, we artificially induced bioelectric potential changes by the surface potential using the fingers. We detected substantial changes in bioelectric potentials through all electrodes during finger touches on the surface of potted Opuntia hybrid plants, although the BDD electrodes were several times more sensitive to bioelectric potential change compared to the other electrodes. Similarly for ground-planted trees, we found that both BDD and Pt electrodes detected bioelectric potential change induced by changing environmental factors (temperature and humidity) for months without replacing/removing/changing electrodes, BDD electrodes were 5-10 times more sensitive in this detection than Pt electrodes. Given these results, we conclude that BDD electrodes on live plant tissue were able to consistently detect bioelectrical potential changes in plants.

Tech Support

Original Source

DOI: https://doi.org/10.3390/s151026921

References

1968 - Evidence of a primary perception in plant life
2007 - Electrical signals and their physiological significance in plants [Crossref]
2009 - Monitoring system for electrical signals in plants in the greenhouse and its applications [Crossref]
1991 - Individuality in the anomalous bioelectric potential of silk trees prior to earthquakes
2007 - Fabrication, characterization, and application of boron-doped diamond microelectrodes for in vivo dopamine detection [Crossref]
2013 - Application of boron-doped diamond microelectrodes for dental treatment with pinpoint ozone-water production [Crossref]