HARKE SFT-D2 Advanced Automatic Surface Tensiometer

Overview

The HARKE SFT-D2 Advanced Automatic Surface Tensiometer is a precision-engineered instrument designed for high-reproducibility measurement of surface and interfacial tension using the du Noüy ring and Wilhelmy plate methods—both standardized under ASTM D971, ISO 6295, ISO 1409, and DIN 53914. Based on electromagnetic balance force transduction, the system eliminates mechanical drift associated with torsion-wire mechanisms, delivering stable, zero-drift measurements across extended test durations. Its integrated embedded computing architecture replaces external PCs while maintaining full functionality—including real-time force profiling, automated meniscus detection, and dynamic parameter adjustment during measurement cycles. The instrument operates on the fundamental principle of quantifying the maximum pull force required to detach a calibrated platinum-iridium ring or plate from a liquid–air or liquid–liquid interface, converting this force into surface tension (mN/m) via geometric correction factors and calibration constants traceable to NIST-certified reference standards.

Key Features

• Electromagnetic balance sensor with 0–120 g capacity and ±0.01 mN/m display resolution, ensuring long-term stability and minimal thermal drift
• Dual-method compliance: Wilhelmy plate (ASTM D971 Annex A3/A4) and du Noüy ring (ISO 6295 Annex B), both implemented with standardized geometries per ISO 1409
• Motorized vertical stage with programmable speed (0–10 mm/sec) and sub-millimeter positioning accuracy (±0.1 mm) over 80 mm travel range
• Integrated temperature-controlled sample environment (0–98 °C) via external recirculating chiller interface; optional electric heating module available for closed-loop bath integration
• Multi-functional operation: simultaneous surface/interfacial tension, liquid density (via buoyancy method), powder contact angle (via sessile drop adaptation), and dynamic contact angle analysis
• Self-contained embedded OS with 10.1″ capacitive touchscreen, eliminating dependency on external computers while supporting USB export, network printing, and audit-trail-enabled data logging

Sample Compatibility & Compliance

The SFT-D2 accommodates standard Φ50 mm sample cups and supports aqueous, organic, polymeric, surfactant-laden, and multi-phase systems—including emulsions and micellar solutions. All wetted parts are constructed from corrosion-resistant platinum-iridium alloy (ring/plate) and PTFE-coated stainless steel (stage components), ensuring chemical inertness across pH 1–14 and common solvents. Calibration procedures follow GLP-compliant workflows, with built-in validation routines for force linearity, zero stability, and geometric factor verification. Data integrity meets FDA 21 CFR Part 11 requirements through electronic signatures, time-stamped audit trails, and role-based user access control within the SFT-D software suite. Test reports include full metadata: operator ID, environmental conditions (temperature/humidity), calibration certificate numbers, and raw force vs. displacement curves.

Software & Data Management

The proprietary SFT-D software provides a modular, ISO/IEC 17025-aligned interface for method setup, real-time visualization, statistical analysis, and regulatory reporting. It includes preloaded international test protocols (A3, A4, A5 per ISO 1409), automatic correction algorithms for buoyancy and wetting perimeter, and batch processing for up to 99 samples per sequence. Raw data are stored in encrypted SQLite databases with SHA-256 hashing; export options include CSV, PDF (with digital signature), and XML formats compatible with LIMS integration. Version-controlled firmware updates and method templates support laboratory-wide standardization, while configurable pass/fail thresholds enable automated QC decision logic aligned with internal SOPs or pharmacopeial monographs (e.g., USP ).

Applications

This tensiometer serves core R&D and QA/QC functions across pharmaceutical formulation (surfactant screening, liposome stability), petrochemical analysis (crude oil–water interfacial behavior), coating & ink development (wetting dynamics), food science (emulsion rheology), and nanomaterial dispersion characterization. Its density measurement capability (0–1000 g/cm³) enables concurrent evaluation of formulation density shifts during aging or phase separation. Researchers utilize the dynamic contact angle module to quantify hysteresis in porous media or functionalized surfaces, while the precise dwell-time control (programmable immersion/retraction timing) facilitates kinetic studies of surfactant adsorption at interfaces—critical for understanding foaming, spreading, and film formation mechanisms.

FAQ

Does the SFT-D2 support both static and dynamic surface tension measurements?
Yes—the instrument performs static equilibrium measurements via standard Wilhelmy or du Noüy protocols, and dynamic measurements through controlled immersion/retraction velocity profiles with time-resolved force capture at 100 Hz sampling rate.
Is third-party calibration certification included with shipment?
Each unit ships with a factory-issued calibration certificate traceable to NIST SRM 8491 (water at 20 °C), valid for 12 months; accredited third-party recalibration services are available upon request.
Can the software generate 21 CFR Part 11–compliant audit trails?
Yes—SFT-D implements electronic signatures, immutable activity logs, and role-based permissions as defined in FDA guidance for computerized systems used in regulated environments.
What materials are used for the measuring probes?
Platinum-iridium alloy (90/10 wt%) for rings and plates, manufactured to ISO 1409 dimensional tolerances and certified for surface roughness ≤0.05 µm Ra.
Is the instrument compatible with external thermostats or Peltier modules?
Yes—the system features analog and digital I/O ports for seamless integration with external temperature controllers, including Julabo, Huber, or Lauda recirculating baths.