Primary surface measurement reported
Water contact angle of HPLC-grade water on Whatman® Grade 4 filter paper treated with four permanent-marker colors (blue, black, green, red).
Client Citation Analysis
Development of a Dual-Modal Microfluidic Paper-Based Analytical Device for the Quantitative and Qualitative Detection of The Total Hardness of Water.
This thesis develops a dual‑modal microfluidic paper-based analytical device for water hardness and uses Dropometer-based water contact-angle measurements to evaluate permanent-marker hydrophobic barriers on paper.
At-a-Glance Summary
Dropometer attribution in the paper
Contact angle measurements were determined using the “Dropometer (Droplet Smart Tech Incorporation, Toronto, ON, Canada),” with images captured and analyzed using the installed Sessile mobile application.
How the contact-angle data were used in the study
Contact-angle results were used to compare marker-color hydrophobicity and guide selection of marker colors used to create hydrophobic barriers in the paper-based device, alongside leakage analysis.
Replication / reliability statement
Figure 4-1 caption states each bar represents the mean of three individual experiments ± standard deviation.
Paper Details
Title
Development of a Dual-Modal Microfluidic Paper-Based Analytical Device for the Quantitative and Qualitative Detection of The Total Hardness of Water.
Authors
Oyejide Damilola Oyewunmi
Institution
Thesis (Master of Applied Science, Mechanical Engineering)
Year
2020
License
© Oyejide Damilola Oyewunmi, 2020
What Was Measured
Primary surface / interfacial measurement
Water contact angle measured on permanent-marker-treated Whatman® Grade 4 filter paper using HPLC-grade water, reported at a 10 s timepoint and as a mean over 60 s (Figure 4-1(b)).
Supporting measurements
Elution velocity of water in different grades of paper was measured to support paper-type selection (Figure 4-1(a)). Leakage analysis was performed by dipping marker-fabricated devices into colored water for 4 minutes to evaluate boundary resistance (Figure 4-2).
Contact angle
Dropometer (Droplet Smart Tech Incorporation, Toronto, ON, Canada)
Contact angle image analysis: Installed Sessile mobile application
Reagent transfer
Calibrated Micropipettes (Sartorius)
Device design
Microsoft PowerPoint 2019 software
Device printing
Hewlett-Packard LaserJet P4015× Printer (EconoMode printer setting)
Role of the Dropometer
The Dropometer was used to determine the contact angle of HPLC-grade water on permanent-marker-treated paper substrates. Grade 4 Whatman filter paper was cut into 2×2 cm square sheets, four permanent marker colors were applied, HPLC water was fed into the sample application syringe and an aliquot was ejected on each square sample, and the droplet image was captured and analyzed using the installed Sessile mobile application to obtain contact-angle values.
The resulting contact-angle comparisons supported marker-color selection for creating hydrophobic barriers in the microfluidic paper-based device.
Bring This Measurement Into Your Lab
If you are screening hydrophobic barrier inks on paper substrates, we can show you the same sessile drop contact angle workflow on your samples.
Key Findings
Measured contact angle at 10 s varies with marker color
After 10 seconds, contact angles were observed as 144 deg. (black), 151 deg. (blue), 145 deg. (red), and 158 deg. (green) for HPLC-grade water on marker-treated Whatman® Grade 4 filter paper.
Hydrophobic strength ranking from contact-angle results
Based on the water contact-angle measurements, hydrophobic strength was reported as green marker > blue marker > red marker ≈ black marker.
Short time-window behavior matches the 10 s comparison
Contact angles investigated over 60 seconds showed similar results to the 10-second measurements, and this was linked to marker pigments retaining hydrophobicity over time.
Leakage outcomes differentiate barrier performance by marker color
Devices fabricated with green and blue marker boundaries did not show any sign of leakage, while black and red marker fabricated devices leaked after 4 minutes in colored water.
Contact-angle and leakage screening guided barrier choice
Following wettability and leakage evaluation, the green and blue markers were utilized to create hydrophobic barriers for flow through the device.
Figures & Visuals
What it shows
Shows contact angle measurement over time for black, blue, red, and green markers on Whatman® Grade 4 filter paper, including a 10 s measurement and a mean over 60 s.
What it shows
Shows leakage analysis images for devices fabricated with green, blue, black, and red marker colors.
Why It Matters
In the fabrication optimization workflow for the microfluidic paper-based analytical device, the contact-angle measurements from the Dropometer provided a quantitative basis for comparing the hydrophobic behavior of different permanent-marker inks on the selected paper substrate.
These wettability results were used alongside leakage analysis to justify which marker colors were used to form hydrophobic barriers that support confined flow paths in the device.
Expert Perspective
Practical Takeaways
Marker inks can be screened by contact angle on the target paper
The study measured water contact angle on Whatman® Grade 4 filter paper after applying different marker colors to compare their hydrophobic strength.
Report both a fixed timepoint and a short-duration behavior check
Contact angles were evaluated at 10 seconds and also investigated over 60 seconds to compare marker performance over a short time window.
Pair contact-angle ranking with a boundary stress test
Leakage analysis by dipping devices into colored water for four minutes was used alongside contact-angle results to evaluate barrier resistance.
Use screening outcomes to select barrier materials for fabrication
The thesis uses the combined wettability and leakage outcomes to select green and blue markers for creating hydrophobic barriers in the device.
Frequently Asked Questions
What did the Dropometer measure in this thesis?
The thesis used the Dropometer (Droplet Smart Tech Incorporation) to measure the contact angle of HPLC grade water on Whatman Grade 4 filter paper treated with blue, black, green and red permanent markers. Droplet images were captured and analysed with the installed Sessile mobile application, at 10 seconds and over 60 seconds.
What contact angles were reported?
At 10 seconds the thesis reports 144° for the black marker, 151° for blue, 145° for red and 158° for green, with each bar in Figure 4-1(b) the mean of three experiments ± standard deviation. Measurements over 60 seconds gave similar results, which the author relates to the marker pigments retaining their hydrophobicity over time.
How were the contact angle results used?
From the contact angles, the author ranks hydrophobic strength as green, then blue, then red and black at about the same level. In a separate leakage test, devices with green and blue marker barriers showed no leakage after 4 minutes in colored water while black and red devices leaked, so green and blue markers were used for the hydrophobic barriers.