The Droplet Lab DROPOMETER‑M was used as a wettability/quality-control screen for LIG electrode surfaces by measuring static contact angle using a 2 µL sessile droplet placed on the LIG working area (Section 2.4). Because the LIG surface produced large fitting errors with axisymmetric Young–Laplace methods, the authors used a non-axisymmetric polynomial method for contact-angle calculation and archived the images (Section 2.4).

In the Electrical & Electronics context, this is significant because contact angle provides a fast, non-destructive indicator of surface state and process consistency for laser-processed carbon electrodes—helping teams detect when manufacturing conditions (e.g., long print runs, laser downtime/maintenance) begin to degrade uniformity (Section 3.1; Figure 1).

Where the paper explicitly ties wettability to liquid/surface-tension behavior:
In Section 3.1, the authors note that common buffers (HEPES, MES, Tris) lower contact angle versus DI water and interpret this as surfactant-like behavior impacting interfacial conditions; however, surface tension is not directly measured.

• Bare LIG wettability is consistent under controlled batching: In DI water, LIG showed a mean contact angle of ~58.6° (hydrophilic) with <5% within-batch variation when fabricated in smaller batches (Section 3.1; Figure 1D).
• Long production runs can break wettability consistency: A single-day run of 36 electrodes caused >30% contact-angle variation; splitting production into four batches of nine with laser downtime reduced variation to <5% (Section 3.1).
• Electrolyte/buffer choice changes wetting behavior: HEPES, MES, and Tris reduced contact angle compared with DI, consistent with surfactant-like effects that can alter the electrode–electrolyte interface during electronics-grade sensor testing (Section 3.1; Figure 1B).
• Metallization shifts surface wetting: After nanoplatinum deposition, contact angle increased to ~78° (more hydrophobic), indicating a meaningful surface-property change relevant to fluid handling and sensor interface design (Section 3.1; Figure 1C/E).
• Electrochemical conditioning requirements differ by configuration: Peak oxidative current stabilized after ~4 CV scans for single LIG electrodes vs ~2 scans for the LIG sensor-chip format (Section 3.2; Figure 2).

Performance vs repeatability tradeoff is real for scaling: Pt metallization increased peak current/capacitance proxies but batch variation increased substantially (discussion around Sections 3.3–3.4; Figure 5C), emphasizing the need for QC gates before high-volume electronics production.

For manufacturers scaling printed/flexible electrochemical sensors or other LIG-enabled microelectronic components, contact angle is a practical incoming/inline QC metric: it quickly flags changes in surface condition that can affect electrolyte wetting, interfacial stability, and ultimately device-to-device variability. This paper shows that process controls (batch sizing, laser downtime/maintenance) can dramatically improve wettability consistency, and that metallization methods should be selected with an explicit tradeoff mindset—balancing improved electrochemical performance against increased batch variability that complicates production specs and yields.