Primary surface measurement reported
Static sessile-droplet contact-angle (hydrophobicity) measurements were performed on LIG electrode surfaces using 5 µl droplets of buffer solutions and DI water.
Client Citation Analysis
Laser Inscribed Graphene Aptasensor for Detection of Apple Stem Pitting Virus
This thesis develops a laser-inscribed graphene (LIG) electrochemical aptasensor platform for apple stem pitting virus and includes sessile-drop contact-angle goniometry to assess LIG surface hydrophobicity.
At-a-Glance Summary
Dropometer attribution in the paper
Hydrophobicity was analyzed using a Droplet lab DROPOMETER-M (Markham, ON, Canada), with contact angles calculated from a static sessile-droplet image using a polynomial (non-axisymmetric drop) method.
How the surface-tension / contact-angle data were used in the study
Goniometry was conducted to determine the hydrophobicity of LIG and nPt-LIG surfaces as part of the thesis’ surface characterization work (with methods and results provided in the appendix).
Paper Details
Title
Laser Inscribed Graphene Aptasensor for Detection of Apple Stem Pitting Virus
Authors
Yifan Tang
Journal
Clemson University — All Theses (Clemson OPEN / TigerPrints)
Year
2023
Pages / Article
All Theses. 4064.
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Role of the Dropometer
The thesis uses a sessile-droplet goniometry workflow to evaluate hydrophobicity on LIG electrodes. After LIG fabrication and preparation, electrodes were stabilized on the instrument platform using mounts, a 5 µl aliquot of buffer (MES pH 6.2, Tris pH 6.6, HEPES pH 7.5, 2X bicarbonate buffer pH 7.8) or DI water was pipetted onto the working area, and the instrument camera captured a static image in sessile droplet mode for contact-angle calculation. In software, key image features (e.g., edges) were identified following manufacturer recommendations, and contact angles were calculated using a polynomial (non-axisymmetric drop) method.
In the thesis’ surface characterization work, the contact-angle output is used to describe the hydrophobicity of LIG and nPt-LIG electrode surfaces.
Key Findings
Sessile-droplet contact-angle workflow on LIG
The thesis measures hydrophobicity by pipetting a 5 µl droplet onto the LIG electrode working area and capturing a static image in sessile droplet mode for contact-angle calculation.
Multiple aqueous buffers and DI water were tested
Contact-angle measurements were carried out using MES (pH 6.2), Tris (pH 6.6), DI water, HEPES (pH 7.5), and 2X bicarbonate buffer (pH 7.8).
Image feature selection followed manufacturer recommendations
The analysis workflow includes identifying key features in the droplet image (e.g., edges) within the software according to manufacturer recommendations.
Polynomial fitting was used for contact-angle calculation on LIG
Contact angle calculations were based on the polynomial (non-axisymmetric drop) method, with the thesis noting that Young–Laplace (axisymmetric) fitting showed significant error for the LIG surface.
Figures & Visuals
Figure 3.2 — Electrode geometry context for droplet placement
What it shows
Shows the design of the single LIG electrode and the biochip layout, providing context for the “working area” referenced in the goniometry workflow.
Figure 3.3 — Surface preparation and passivation context
What it shows
Illustrates the schematic preparation of the single LIG electrode and biochip, including passivated regions and connection areas associated with the sensor platform.
Figure S.1 — Contact-angle calculation concept used in the analysis
What it shows
Provides a schematic “polynomial method illustration” showing a buffer drop on a surface with the tangent and contact angle (θ) indicated.
Why It Matters
The thesis includes contact-angle goniometry as part of its surface characterization work for LIG-based electrodes used in an electrochemical aptasensor platform. By reporting a defined sessile-droplet workflow (drop volume, test liquids, imaging mode, and analysis approach), the study documents how hydrophobicity was assessed on the electrode material.
These surface measurements are presented alongside electrokinetic analysis used to determine surface charge (zeta potential), collectively describing key surface properties of LIG and nPt-LIG in the thesis’ materials characterization.
Practical Takeaways
Defined sessile-droplet imaging mode
The study uses a static-image sessile droplet approach for contact-angle analysis on LIG electrodes.
Buffer-dependent wetting checks
Hydrophobicity was assessed using multiple aqueous solutions (MES, Tris, HEPES, 2X bicarbonate buffer) plus DI water, each with the pH specified for the buffers.
Small-volume droplet protocol
A consistent 5 µl aliquot was used for each contact-angle measurement condition described.
Polynomial contact-angle computation for LIG
Contact angles were calculated using a polynomial (non-axisymmetric) method, with the workflow explicitly describing feature identification (e.g., edges) and the fitting approach used for this surface.