Enhanced physicochemical properties of polydimethylsiloxane based microfluidic devices and thin films by incorporating synthetic micro-diamond

At a Glance

Metadata	Details
Publication Date	2017-11-03
Journal	Scientific Reports
Authors	Sidra Waheed, Joan M. Cabot, Niall P. Macdonald, Umme Kalsoom, Syamak Farajikhah
Institutions	ARC Centre of Excellence for Electromaterials Science, University of Wollongong
Citations	55
Analysis	Full AI Review Included

Technical Analysis and Documentation: Enhanced Thermal Management in Microfluidics using MPCVD Diamond Composites

This document analyzes the research paper, “Enhanced physicochemical properties of polydimethylsiloxane based microfluidic devices and thin films by incorporating synthetic micro-diamond,” and provides a pathway for engineers and researchers to leverage 6CCVD’s advanced CVD diamond materials to replicate or extend these achievements.

Executive Summary

This study successfully demonstrates the use of synthetic micro-diamond powder to dramatically improve the thermal and mechanical properties of Polydimethylsiloxane (PDMS) microfluidic devices, directly addressing critical thermal management challenges in Lab-on-a-Chip (LOC) systems.

Thermal Performance: Incorporation of 60 wt% micro-diamond (PD60 composite) resulted in a three-fold increase in thermal conductivity, reaching 0.45 W m^-1 K^-1 (vs. 0.15 W m^-1 K^-1 for pure PDMS).
Heat Dissipation Efficiency: The PD60 composite chip achieved a 9.8 °C temperature drop across a 3 cm channel at 1000 µL/min flow rate, representing more than twice the heat dissipation capability of pure PDMS chips.
Mechanical Enhancement: Elastic modulus increased significantly from 1.28 MPa (control) to 4.42 MPa (PD60 composite), enhancing the structural rigidity and durability of the microfluidic platform.
Fabrication Method: Devices were successfully produced using indirect 3D printing (Cast and Peel) for chips and spin coating for thin film cover layers (160 µm).
Application Relevance: This high-performance composite is immediately applicable for thermally sensitive micro-systems, including integrated electronics, MEMS, and Polymerase Chain Reaction (PCR) chips.

Technical Specifications

The following hard data points were extracted from the research paper, focusing on the performance improvements achieved by the optimal 60 wt% micro-diamond composite (PD60).

Parameter	Value	Unit	Context
Diamond Filler Concentration	60	wt%	Optimal PDMS/Micro-Diamond Composite (PD60)
Diamond Particle Size	2 - 4	µm	Industrial non-porous HPHT micro-diamond powder
Thermal Conductivity (k)	0.45	W m^-1 K^-1	PD60 composite (3x increase over PDMS control)
Elastic Modulus	4.42	MPa	PD60 composite (vs. 1.28 MPa for PDMS control)
Thermal Degradation Onset	310	°C	PD60 composite (Increased thermal stability)
Microchannel Temperature Drop ($\Delta$T)	9.8	°C	Across 3 cm channel at 1000 µL/min flow rate
Flow Rate (Max Tested)	1000	µL/min	Heated Milli-Q water
Thin Film Cover Thickness	160	µm	Spin-coated top layer, used for bonding
Chip Thickness (Thermal Test)	5	mm	Sample dimension for thermal conductivity measurement
Contact Angle (Thin Film, PD60)	81 $\pm$ 5	°	Reduced hydrophobicity compared to PDMS control (113.7°)

Key Methodologies

The fabrication of the thermally enhanced PDMS/micro-diamond microfluidic chips relied on indirect 3D printing (Cast and Peel) coupled with specific material handling techniques to ensure homogeneous particle dispersion.

Diamond Preparation: Industrial non-porous high-pressure/high-temperature (HPHT) micro-diamond powder (2-4 µm) was purified and used as the composite filler.
Composite Formulation: Micro-diamond powder was mixed with PDMS monomer (up to 60 wt% loading).
Dispersion: The PDMS/diamond mixture was subjected to intensive 4 hours of sonication followed by 30 minutes of vacuum degassing to ensure micro-particle homogeneity and remove trapped air bubbles.
Template Fabrication: 3D-printed templates (DLP-SLA) with 500 µm channels were created, post-cured (UV and isopropanol soak), and then silanized (using fluorinated silane in vacuum) to prevent PDMS adhesion.
Casting and Curing: The composite mixture was poured onto the silanized template, cured in an oven at 70 °C for 2 hours, and subsequently peeled off.
Thin Film Preparation (Cover Layer): Identical composite mixtures were prepared and applied onto a PMMA substrate using spin coating (30 sec under vacuum) to achieve a 160 µm thin film cover layer.
Bonding: The composite chip body and the thin film cover were bonded using laboratory corona treatment.

6CCVD Solutions & Capabilities

6CCVD provides the high-performance MPCVD diamond materials necessary to replicate, optimize, and scale the enhanced thermal management demonstrated in this research. Our advanced materials offer superior purity and thermal properties compared to standard HPHT powders used here, enabling greater performance and integration potential.

Applicable Materials for Thermal Management Applications

Research Application Requirement	6CCVD Material Recommendation	Thermal/Mechanical Advantage
High Thermal Composites / Bulk Filler	High-Purity Polycrystalline Diamond (PCD) Powder	Provides exceptional $k$ (up to 1000 W m^-1 K^-1) in composite matrix; high purity ensures robust bonding and predictable thermal properties.
High-Performance Heat Sinking Substrate	Single Crystal Diamond (SCD) Wafers	Highest available thermal conductivity (up to 2200 W m^-1 K^-1). Ideal for use as the primary cooling substrate beneath the PDMS microchannel layer (for applications like high-power PCR or integrated electronics).
Integrated Heating/Sensing Elements	Boron-Doped Diamond (BDD)	Customizable doping levels allow integration of thermally robust heating elements or electrochemical sensors directly into the microfluidic stack, eliminating external heating components.

Customization Potential for Microfluidic Systems

6CCVD’s specialized fabrication capabilities ensure that material requirements for advanced microfluidic thermal solutions can be met precisely, regardless of complexity or scale.

Custom Dimensions: While the paper used 5 mm thick chips, 6CCVD offers high-quality PCD plates/wafers up to 125 mm diameter. This scale allows for complex, inch-size microfluidic platforms with consistent thermal properties.
Thin Film Requirements: The 160 µm thin film cover layer used in this study is well within our standard capability. 6CCVD supplies SCD and PCD films ranging from 0.1 µm up to 500 µm thickness, optimized for minimal thermal resistance.
Precision Finishing: The study highlights the need for consistent surface quality for reliable bonding. Our in-house polishing guarantees exceptional smoothness: Ra < 1 nm (SCD) and Ra < 5 nm (PCD) on inch-size substrates.
Metalization Services: Although not featured in this specific paper, many advanced electrofluidic systems require integrated heaters or contacts. 6CCVD offers in-house metalization (Au, Pt, Pd, Ti, W, Cu) for direct integration onto diamond substrates, supporting complex MEMS or electro-osmotic flow applications.

Engineering Support

This research validates diamond as the ideal material for enhanced heat dissipation in PDMS microfluidics. 6CCVD’s in-house PhD team provides consultative support to optimize material selection, thickness, and integration techniques (e.g., bonding, surface functionalization) for similar thermally managed LOC and microreactor 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/s41598-017-15408-3