Nanoelectrode Arrays Fabricated by Thermal Nanoimprint Lithography for Biosensing Application

At a Glance

Metadata	Details
Publication Date	2020-08-05
Journal	Biosensors
Authors	Alessandra Zanut, Alessandro Cian, Nicola Cefarin, Alessandro Pozzato, Massimo Tormen
Institutions	AREA Science Park, University of Trieste
Citations	22
Analysis	Full AI Review Included

Technical Documentation & Analysis: MPCVD Diamond for High-Throughput Biosensing

This document analyzes the research paper “Nanoelectrode Arrays Fabricated by Thermal Nanoimprint Lithography for Biosensing Application” by Zanut et al. (2020) and outlines how 6CCVD’s specialized MPCVD diamond materials and fabrication services can support and scale this advanced electrochemical biosensing technology.

Executive Summary

The research successfully demonstrates a high-sensitivity electrochemical biosensor platform utilizing Nanoelectrode Arrays (NEA) fabricated on Boron-Doped Diamond (BDD) macroelectrodes.

Core Achievement: Fabrication of highly reproducible NEA structures (265 nm diameter, 800 nm period) on BDD using low-cost, high-throughput Thermal Nanoimprint Lithography (TNIL).
Material Synergy: The combination of BDD (as the robust, conductive electrode) and Polycarbonate (PC) (as the functionalizable dielectric layer) enables independent optimization of electrochemical and molecular recognition properties.
Electrochemical Performance: The NEA structure, leveraging BDD’s properties, effectively suppresses the capacitive background signal, leading to enhanced sensitivity and improved detection limits for biomolecules.
Application Demonstrated: Successful detection of gliadin protein fragments (a gluten marker) via cyclic voltammetry in the concentration range of 0.5-10 µg/mL, with a linear response identified up to 0.5 µg/mL.
Scalability: The use of TNIL, coupled with the inherent stability of CVD diamond, positions this platform for industrial scale-up in food and biomedical monitoring applications.
6CCVD Value Proposition: 6CCVD provides the necessary high-quality, custom-doped BDD substrates and advanced polishing/metalization services required to replicate and industrialize this high-resolution nanofabrication process.

Technical Specifications

The following hard data points were extracted from the research paper detailing the device structure and performance metrics.

Parameter	Value	Unit	Context
Electrode Material	Boron-Doped Diamond (BDD)	N/A	Conductive layer for NEA fabrication
BDD Film Thickness	400	nm	Thickness of CVD BDD layer on Si <100>
Dielectric Material	Polycarbonate (PC)	N/A	Resist film used for TNIL and functionalization
PC Film Thickness	220	nm	Average thickness of spin-coated PC layer
NEA Dot Diameter (Average)	265	nm	Diameter of the resulting nanoelectrodes
NEA Interspacing/Period	800	nm	Center-to-center distance between nanoelectrodes
TNIL Imprinting Pressure	10	MPa	Applied pressure during thermomechanical cycle
TNIL Imprinting Temperature	180	°C	Temperature used during imprinting
TNIL Imprinting Time	10	min	Duration of the imprinting step
Gliadin Detection Range	0.5-10	µg/mL	Overall concentration range tested
Linear Response Range	≤0.5	µg/mL	Optimized linear detection range (R² = 0.86)
Electrochemical Technique	Cyclic Voltammetry (CV)	N/A	Transduction method used for detection
CV Scan Rate	50	mV s^-1	Rate used for voltammetric measurements

Key Methodologies

The fabrication of the NEA platform relies on precise material deposition and controlled thermal nanoimprint lithography (TNIL) followed by plasma etching.

Substrate Preparation: Si <100> wafers were coated with a 400 nm thick layer of Boron-Doped Diamond (BDD) via CVD to serve as the macroelectrode.
Dielectric Coating: A 4% w/v Polycarbonate (PC) solution in cyclopentanone was spin-coated onto the BDD, followed by annealing at 180 °C for 30 minutes to yield a 220 nm thick film.
Stamp Fabrication: A silicon master (800 nm period, 400 nm diameter) was replicated and functionalized with octyl-trichlorosilane for non-stick release.
Thermal Nanoimprint Lithography (TNIL): The stamp was pressed onto the PC film at 10 MPa pressure for 10 minutes at 180 °C, creating recessed nanoholes in the polymer layer.
Residual Layer Removal: The residual PC layer remaining at the bottom of the nanoholes was removed using a short Oxygen Plasma etching step (4 seconds, 4 mT pressure, 200 W coil power, 10 W platen power).
Surface Activation: The PC surface was activated by dipping the NEA in 5 M NaOH solution for 1 minute, promoting the deprotonation of surface groups to enhance hydrophilicity and subsequent gliadin physisorption.
Immunosensing: The activated NEA was used to immobilize gliadin, followed by sequential binding of primary anti-gliadin IgG and HRP-labeled secondary antibody. Detection was performed via CV using Methylene Blue (MB) as a redox mediator and H₂O₂ as the enzyme substrate.

6CCVD Solutions & Capabilities

This research highlights the critical role of high-quality BDD substrates in creating advanced electrochemical sensors. 6CCVD is uniquely positioned to supply the materials and customization required to industrialize this NEA platform.

Applicable Materials

To replicate and extend this research, the primary material requirement is a highly conductive, robust diamond electrode suitable for subsequent nanofabrication.

Material Recommendation: Heavy Boron Doped PCD (Polycrystalline Diamond) or SCD (Single Crystal Diamond).
- PCD Advantage: Offers the best balance of large area capability (up to 125 mm wafers) and cost-effectiveness for high-throughput TNIL processes.
- SCD Advantage: Provides superior crystalline uniformity, potentially reducing variability in electrochemical response across the array, ideal for ultra-high precision applications.
Doping Control: 6CCVD offers precise control over boron doping levels, ensuring the BDD film maintains the low capacitive background and wide potential window essential for sensitive biosensing applications.

Customization Potential

The scalability of this TNIL-based process requires access to custom, high-quality substrates.

Research Requirement	6CCVD Capability	Technical Benefit for Biosensing
Substrate Size (Used 25 x 25 mm²)	Custom plates and wafers available up to 125 mm (PCD).	Enables industrial scale-up and high-volume manufacturing of NEA sensors using high-throughput TNIL.
Precise Thickness Control (400 nm BDD)	SCD and PCD thickness control from 0.1 µm up to 500 µm.	Guarantees consistent electrical properties and minimizes material waste, crucial for thin-film electrode fabrication.
Surface Quality (Required for uniform spin-coating)	Advanced polishing services achieving Ra < 5 nm (PCD) and Ra < 1 nm (SCD).	Ensures optimal uniformity of the spin-coated PC dielectric layer, which is critical for successful, defect-free nanoimprint patterning.
Integrated Electrodes (Future miniaturization)	In-house metalization services: Au, Pt, Pd, Ti, W, Cu.	Allows for the integration of on-chip reference and counter electrodes directly onto the diamond substrate, creating a complete, miniaturized three-electrode system.

Engineering Support

The successful implementation of this NEA platform relies on optimizing the interface between the BDD electrode and the PC dielectric layer.

Expert Consultation: 6CCVD’s in-house PhD team specializes in CVD diamond surface chemistry and electrochemical applications. We can assist researchers in optimizing BDD material selection, doping profiles, and surface preparation techniques (e.g., plasma treatment, termination) to maximize the signal-to-noise ratio for similar electrochemical immunosensor projects.
Global Logistics: We offer reliable global shipping (DDU default, DDP available) to ensure timely delivery of custom diamond substrates worldwide, supporting international research and development efforts.

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

View Original Abstract

Electrochemical sensors are devices capable of detecting molecules and biomolecules in solutions and determining the concentration through direct electrical measurements. These systems can be miniaturized to a size less than 1 µm through the creation of small-size arrays of nanoelectrodes (NEA), offering advantages in terms of increased sensitivity and compactness. In this work, we present the fabrication of an electrochemical platform based on an array of nanoelectrodes (NEA) and its possible use for the detection of antigens of interest. NEAs were fabricated by forming arrays of nanoholes on a thin film of polycarbonate (PC) deposited on boron-doped diamond (BDD) macroelectrodes by thermal nanoimprint lithography (TNIL), which demonstrated to be a highly reliable and reproducible process. As proof of principle, gliadin protein fragments were physisorbed on the polycarbonate surface of NEAs and detected by immuno-indirect assay using a secondary antibody labelled with horseradish peroxidase (HRP). This method allows a successful detection of gliadin, in the range of concentration of 0.5-10 μg/mL, by cyclic voltammetry taking advantage from the properties of NEAs to strongly suppress the capacitive background signal. We demonstrate that the characteristics of the TNIL technology in the fabrication of high-resolution nanostructures together with their low-cost production, may allow to scale up the production of NEAs-based electrochemical sensing platform to monitor biochemical molecules for both food and biomedical applications.

Tech Support

Original Source

DOI: https://doi.org/10.3390/bios10080090

References

2008 - Electrochemical sensors for clinic analysis [Crossref]
2010 - Electrochemical biosensors [Crossref]
2016 - Nanomaterials in electrochemical biosensors for pesticide detection: Advances and challenges in food analysis [Crossref]
2001 - Electrochemical biosensors: Recommended definitions and classification
2015 - Electrochemical Sensors and Biosensors Based on Nanomaterials and Nanostructures [Crossref]
2006 - Electrochemical sensors [Crossref]
2013 - Development of electrochemical biosensors by e-beam lithography for medical diagnostics [Crossref]
2004 - Nanoelectrodes, nanoelectrode arrays and their applications [Crossref]
2006 - Mapping electrochemiluminescence as generated at double-band microelectrodes by confocal microscopy under steady state [Crossref]