Contents

Pharmaceutical Industry
The Practical Guide to Surface Science (2026)

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Written by
Dr Amit Pratap Singh
PhD, Delhi University Post Doc - AIST Japan
Guest Author
Read More
alidad
Reviewed by
Dr Alidad Amirfazli
Dr. Amirfazli, a leading expert in surface wetting and superhydrophobic coatings, has 250+ publications, edits Advances in Colloid and Interface Science, and has received multiple research awards.
Scientific Advisor & Co-founder
Read More
D54c15105cfe94f786c500e4091d6ea65457608fde49ba183c8f862814a54249?s=100&d=m
Written By

Dr Amit Pratap Singh

Guest Author

PhD, Delhi University

Post Doc - AIST Japan

alidad
Reviewed By

Dr Alidad Amirfazli

Scientific Advisor & Co-founder

Dr. Amirfazli, a leading expert in surface wetting and superhydrophobic coatings, has 250+ publications, edits Advances in Colloid and Interface Science, and has received multiple research awards.

Featured Studies & Publications

Research Paper Contact angle measurement with a smartphone
Research Paper Surface tension measurement with a smartphone using a pendant drop

This is a practical guide to Surface Science for researchers working in the Pharmaceutical Industry.

In this all-new guide you’ll learn all about:

  • Crucial surface science principles
  • The significance of surface science measurements for the Pharmaceutical industry
  • Applicable ASTM Standards & Guidelines

Let’s dive right in.

Pharmaceutical Products

Contents

measurement

Contact Angle Measurement

tension

Surface Tension Measurement

energy

Surface Energy Measurement

sliding angle

Sliding Angle Measurement

realworld

Real World Applications

standardand guide

Standards and Guidelines

Executive Summary

What it covers: How pharmaceutical formulation, process and QC teams use surface and interfacial tension, contact angle, surface free energy and sliding angle. Each measurement is tied to a real problem, such as excipient choice, spray drying, cleaning checks or vesicle yield.
Key insights: Small formulation changes shift surface tension, which affects the droplets a spray dryer or inhaler produces. A study run on Harvard’s shared Dropometer found that lower oil and buffer interfacial tension tracked with higher lipid vesicle yield. Contact angle on a tablet compact shows how readily a solid dosage form wets.
Business value: Measuring surface tension in house lets formulation scientists see how each excipient changes a formulation before slower droplet size or dissolution work. One portable kit covers all four measurements, so it can sit at the formulation bench rather than in a shared lab.
Standards to follow: USP ⟨1243⟩ is a proposed chapter on wetting of pharmaceutical systems by contact angle and surface or interfacial tension. It is not yet an enforceable requirement. FDA 510(k) guidance for contact lens care products describes finding the critical micelle concentration by surface tension. Check the status and edition of each before you rely on it.
Bottom line: Measure surface tension while you formulate liquids and spray drying feeds, and contact angle once a solid dosage form or device surface is involved. Start with the measurement that matches your failure, then book a 15 minute demo to try it on your own samples.

Chapter 1: Introduction

In pharmaceutical work, many development delays start at an interface. A formulation change that shifts surface tension changes the droplets a spray dryer or inhaler makes. A residue film left after cleaning can carry over into the next batch.

These are the places where wetting decides yield in pharmaceutical work:

The Dropometer surface tension and contact angle kit measures contact angle, surface and interfacial tension, surface free energy and sliding angle with one portable setup. Its method was validated against a KRUSS DSA100E in two peer reviewed papers. If you are new to the terms, start with wettability.

We use the following surface properties to understand the behavior of Pharmaceutical products and improve their quality.

Chapter 2: Contact Angle Measurement

The contact angle quantifies the wettability of a surface by representing the angle between a liquid’s surface and a solid surface.
Dropletlab Research

Sample Image taken from Droplet Lab Tensiometer.

Young – Laplace Method

  • 1. This method uses the whole drop profile to calculate the contact angle value.
  • 2. This method is only compatible with an axisymmetric drop, which is not always seen in practice because a needle is typically inserted into the drop to increase or decrease the drop volume.
  • 3. This method yields more consistent results than the polynomial fitting method.

Polynomial Method

  • 1. This method uses only a portion of the drop profile to calculate the contact angle value.
  • 2. This method is compatible with both axisymmetric and non-axisymmetric drops.
  • 3. The measurement results of this method are less consistent, as they can be influenced by local surface imperfections.
Dynamic Contact Angle

Ideally, when we place a drop on a solid surface, a unique angle exists between the liquid and the solid surface. We can calculate the value of this ideal contact angle (the so-called Young’s contact angle) using Young’s equation. In practice, due to surface geometry, roughness, heterogeneity, contamination, and deformation, the contact angle value on a surface is not necessarily a single consistent value but rather falls within a range. The upper and lower limits of this range are known as the advancing and receding contact angles, respectively. The values of advancing and receding contact angles for a solid surface are highly sensitive to many parameters, such as temperature, humidity, homogeneity, and minor contamination of the surface and liquid. For example, the advancing and receding contact angles of a surface can differ at different locations.

Dynamic Contact Angle versus Static Contact Angle

Practical surfaces and coatings naturally show contact angle hysteresis, indicating a range of equilibrium values. When we measure static contact angles, we get a single value within this range. Solely relying on static measurements poses problems, like poor repeatability and incomplete surface assessment regarding adhesion, cleanliness, roughness, and homogeneity.

In practical applications, we need to understand how easily a liquid spreads (advancing angle) and how easily it is removed (receding angle), such as in painting and cleaning. Measuring advancing and receding angles offers a holistic view of liquid-solid interaction, unlike static measurements, which yield an arbitrary value within the range.

This insight is crucial for real-world surfaces with variations, roughness, and dynamics, aiding industries like cosmetics, materials science, and biotechnology in designing effective surfaces and optimizing processes.

Learn how Contact Angle measurement is done on our Tensiometer

For a more complete understanding of Contact Angle measurement, read our Contact Angle measurement: The Definitive Guide

Contact Angle measurement: The Definitive Guide

Open Benchmark Data: Contact Angle & Surface Energy

These reference measurements show how deionized water wets four standard substrates measured with the Droplet Lab Dropometer. Use them as visual and numerical benchmarks when you're checking your own sample preparation, treatments, and chemistry.

Full contact angle and surface energy datasets (including additional liquids and statistics) are available on our dataset hub.

Glass - DI Water
Glass - DI Water
Nylon - DI Water
Nylon - DI Water
PMMA - DI Water
PMMA - DI Water
Teflon - DI Water
Teflon - DI Water

The droplet images above are taken from the same benchmark series as our open dataset. For each substrate and probe liquid we report:

● Advancing and receding contact angles (and hysteresis)
● Derived surface energy (SFE) values based on multi-liquid measurements
● Measurement conditions, uncertainties, and sample preparation details

Comparing your own droplet shapes and angles against these references is a fast way to spot contamination, treatment drift, or unexpected changes in wettability.

Explore the full benchmark datasets (contact angle + surface energy)

Measurements were performed with the Droplet Lab Dropometer under controlled laboratory conditions. Treat these values as sanity checks and starting points for your own process targets, not as product specifications.

Chapter 3: Surface Tension Measurement

This property measures the force that acts on the surface of a liquid, aiming to minimize its surface area.

Surface Tension Measurement

Sample Image taken from Droplet Lab Tensiometer

Dynamic Surface Tension

Dynamic surface tension differs from static surface tension, which refers to the surface energy per unit area (or force acting per unit length along the edge of a liquid surface).

Static surface tension characterizes the equilibrium state of the liquid interface, while dynamic surface tension accounts for the kinetics of changes at the interface. These changes could involve the presence of surfactants, additives, or variations in temperature, pressure, and composition at the interface.

When to use Dynamic Surface Tension Measurement

Dynamic surface tension is essential for processes that involve rapid changes at the liquid-gas or liquid-liquid interface, such as droplet and bubble formation, coalescence (change in surface area), the behavior of foams, and the drying of paints (change in composition, e.g., evaporation of solvent). It is measured by analyzing the shape of a hanging droplet over time.

Dynamic surface tension applies to various industries, including cosmetics, coatings, pharmaceuticals, paint, food and beverage, and industrial processes, where understanding and controlling the behavior of liquid interfaces is essential for product quality and process efficiency.

Learn how Surface Tension measurement is done on our Tensiometer

For a more complete understanding of Surface Energy measurement, read our Surface Tension measurement: The Definitive Guide

Surface Tension measurement: The Definitive Guide

Chapter 4: Surface Energy Measurement

Surface energy refers to the energy required to create a unit area of a new surface.
231

Sample Image taken from Droplet Lab Tensiometer

Learn how Surface Energy measurement is done on our Tensiometer

For a more complete understanding of Surface Energy measurement, read our Surface Energy measurement: The Definitive Guide

Surface Energy measurement: The Definitive Guide

For benchmark contact angle and surface energy values on glass, nylon, PMMA, and Teflon, see the Open Benchmark Data panel above or visit our Dataset Hub for full CSV downloads.

Dataset Hub

Chapter 5: Sliding Angle Measurement

The sliding angle measures the angle at which a liquid film slides over a solid surface. It is commonly employed to assess the slip resistance of a surface.

sliding angle 1

Sample Image taken from Droplet Lab Tensiometer

Learn how Sliding Angle measurement is done on our Tensiometer

For a more complete understanding of Sliding Angle measurement, read our Sliding Angle Measurement: The Definitive Guide

Sliding Angle Measurement: The Definitive Guide

Chapter 6: Real-World Applications

Within the Pharmaceutical industry, several case studies exemplify the advantages of conducting surface property measurements.

Engineering Asymmetric Nanoscale Vesicles for mRNA and Protein Delivery to Cells

The paper addresses a common pharmaceutical delivery challenge: therapeutic cargos vary widely, and delivery systems often require tuning to achieve robust performance. The authors present nanoscale lipid vesicles engineered with asymmetric leaflet composition and demonstrate that these vesicles can support delivery of nucleic-acid and protein payload classes in cellular models. A key formulation insight is established by linking interfacial properties of lipid-in-oil systems to vesicle formation outcomes, positioning interfacial tension as a measurable handle relevant to formulation selection and manufacturing robustness.

Role of the Droplet Lab Goniometer

Droplet Lab is used for pendant-drop tensiometry to quantify mineral oil / aqueous PBS interfacial tension for different lipid-containing oil formulations. These values are then interpreted against vesicle formation yield trends, making the Droplet Lab measurement a formulation-screening metric rather than a purely descriptive material property.

What this enables for pharma teams:

  • Objective comparison of lipid formulation “interfacial activity” (how strongly a lipid reduces oil/water interfacial tension)

A quantitative bridge from physicochemical measurement → process outcome (yield), supporting earlier-stage down-selection and comparability thinking.

Key Findings

  • Interfacial tension differs strongly across lipid chemistries in the oil/buffer system (Fig. 3c), demonstrating meaningful separation between candidates by a single quantitative metric.
  • The study reports a correlation between lower interfacial tension and higher vesicle yield, implying interfacial tension can act as an early indicator of formation efficiency.
  • Reported interfacial-tension values span a broad range (e.g., ~61.5 ± 3.5 mN/m for one lipid condition vs markedly lower values for others), providing a practical “screening window” for formulation differentiation.
  • Yield is assessed via fluorescence-linked quantification and is shown to vary substantially by lipid selection, reinforcing the need for formulation screening metrics beyond composition alone.

Why It Matters

In pharmaceutical development, delivery platforms succeed or fail not only on biological performance but on manufacturability, reproducibility, and change control. This paper highlights interfacial tension (measured by pendant drop) as a pragmatic, fast, and quantitative formulation attribute that correlates with formation yield, making it useful for formulation down-selection, comparability assessments, and QC-oriented specifications tied to interface-driven process behavior rather than trial-and-error alone.

Method Snapshot

Measurement mode: pendant-drop tensiometry (Droplet Lab) at an oil-aqueous buffer interface, with interfacial tension obtained by Young-Laplace shape fitting. Temperature is not explicitly stated in the pendant-drop description.

Data Note

Figure 3c: shows the interfacial tension results for water/mineral-oil systems with different lipids (caption notes Mean ± SD, n=3), providing the paper’s core Droplet Lab measurement dataset used to support the yield correlation.

Figure

Citation (APA Format)

Yang, C., Menge, J., Zhvania, N., Yu, M., Yang, H., Chen, D., Zheng, Z., Weitz, D. A., & Jahnke, K. (2025). Engineering asymmetric nanoscale vesicles for mRNA and protein delivery to cells. Advanced Functional Materials, 35, 2505738. https://doi.org/10.1002/adfm.202505738

View Publication →

Oral dosage form development

An oral dosage form must wet before it can dissolve. Contact angle on a tablet compact shows how readily it wets, and surface tension shows how a surfactant or excipient changes the liquid that meets it. USP ⟨1243⟩, a proposed chapter, describes both measurements for pharmaceutical systems.

For surfactant levels, our CMC use case shows how to find the critical micelle concentration from a dilution series. University of Waterloo researchers used the same pendant drop approach on the Dropometer to locate surfactant breaks in cellulose nanocrystal and fumed silica suspensions.

Oral dosage form development

Cleaning and contamination checks in manufacturing

A clean surface and a surface carrying a thin residue can look the same. Water contact angle at fixed spots shows whether cleaning removed organic films from equipment, containers or components, as a quick check alongside your validated cleaning tests.

Our surface cleanliness verification page sets out the test plan. For coated parts, contact angle also shows whether a coating changed the surface. The University of Toronto group showed a polyserotonin coating made glass more hydrophilic, with water contact angle down by over 15 degrees.

Cleaning and contamination checks in manufacturing

Drug delivery systems and device coatings

Drug delivery depends on interfaces, from lipid vesicles and emulsion droplets to coated catheters. Interfacial tension guides lipid and surfactant choice, and contact angle shows whether a coating changed a device surface as intended.

On the Harvard shared facility Dropometer, lower interfacial tension tracked with higher yield of asymmetric vesicles for mRNA and protein delivery. See our lipid vesicle yield page. A Chilean team used water contact angle to show a layer by layer antibiotic coating turned silicone catheters from hydrophobic to hydrophilic.

Drug delivery systems and device coatings

Inhaled and spray dried medicines

Surface tension of an inhaled or spray dried formulation affects the droplets it forms. Excipient, surfactant or concentration changes can shift it, and the effect may only show up later in droplet or particle tests.

A pharmaceutical CDMO now measures formulation surface tension in house to see how each excipient changes a formulation. Its first trials showed that small formulation differences give different values. See the spray drying case study and our inhalable medications page. Surface tension is a screening step and does not measure droplet size or delivered dose.

Inhaled and spray dried medicines

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If you are interested in implementing these or any other applications, please contact us.

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Chapter 7: Standards and Guidelines

In an industry where precision reigns supreme, how can Pharmaceutical manufacturers ensure their products withstand scrutiny? The answer lies in standards and guidelines: the compass that guides them through the complex maze of quality and performance.

USP ⟨1243⟩, Wetting Properties of Pharmaceutical Systems (Proposed General Chapter; PF 49(5))

What it is

A proposed USP general chapter that provides a standardized framework for characterizing wetting-related properties of pharmaceutical systems, most commonly through contact angle-based wettability assessment (solids) and surface/interfacial tension measurement techniques (liquids), along with discussion of influencing factors and related concepts (e.g., surface free energy).

When to use it

Formulation development / optimization

Compare excipient or surfactant options using contact angle and/or γ-log C behavior.

Tech transfer

Replace “looks OK” assessments with numeric, operator-comparable wetting metrics (defined timestamp for θ; defined temperature for γ).

Manufacturing / investigations

When you see batch-to-batch drift in disintegration/dissolution or coating appearance/uniformity and suspect wetting-related causes.

QC trending

Establish baseline and monitor drift in solid-side wettability and liquid-side spreading capability over time.

In-scope / Out-of-scope

In scope
  • Solids Wettability characterization via contact angle (with explicit definition of when the angle is read). Optional use of advancing/receding angles only when repeatable on the substrate.
  • Liquids Surface tension and (when relevant) interfacial tension measurement techniques and factors influencing results.
  • Method context Recognizing/controlling factors that influence measurements (surface heterogeneity, porosity/absorption, temperature, etc.).
Out of scope
  • Universal numeric limits (e.g., “θ must be < X° for all tablets”), wetting targets must be product-/family-calibrated against performance outcomes.
  • Replacing compendial performance tests Wetting data supports understanding and control; it does not replace dissolution/disintegration or coating quality requirements.
  • Forcing unstable metrics If receding angle/hysteresis is not repeatable on rough/porous surfaces, don’t treat it as mandatory evidence.
  • Data-system compliance by default Instrument outputs are only “GMP records” when integrated under your site’s validated controls and procedures.

Minimum you must report (checklist)

  • Sample + context: sample ID (lot/product family), sample type (tablet/compact/coating vs solution/media), and any conditioning/handling (e.g., equilibration) plus the measurement map (faces/regions).
  • Test conditions: temperature (and RH if relevant) at time of test.
  • Traceability: instrument + software version, analysis model/fit method, and operator/SOP identifier.
  • Replicates + stats: n for each metric and the statistic you standardize on (e.g., median + IQR or mean + SD).
  • Solids (contact angle): probe liquid + droplet volume, θ @ fixed timestamp (and any secondary timepoint), spot-to-spot variability (IQR/SD), optional Δθ(t1→t2), and optional θₐ/θᵣ/hysteresis only if repeatable.
  • Liquids (surface/interfacial tension): method geometry (e.g., pendant drop), temperature setpoint, density inputs (and source), γ/IFT result (n + stats), pendant-drop fit/QC acceptance criteria; if reporting CMC, include concentration-series design and breakpoint/estimation method.
  • Data integrity: explicit reject/re-run rules (e.g., failed fit QC, unstable baseline/edge, absorption collapse before timestamp) and system suitability controls (reference tablet + reference liquid with run frequency and acceptance/trending limits).

Dropometer supports wetting characterization aligned with USP ⟨1243⟩ by producing standardized, timestamped θ (solids) and γ/IFT (liquids) with settings captured per run. Whether those records are GMP/audit-ready depends on your site’s validated systems, SOPs, and controls.

How to interpret results (guardrails)

  • Never compare solid θ without matching timestamp + conditioning; porous/absorbing surfaces can change rapidly, so fixed-time θ (and/or Δθ) is the defensible basis.
  • Use median θ @ t plus variability (IQR/SD) to separate “surface wettability shift” from “surface heterogeneity shift,” then confirm significance against your product-family correlation to outcomes.
  • Treat θₐ/θᵣ/hysteresis as optional diagnostics only when the substrate yields stable, repeatable values, don’t force it on rough/absorbing tablets.
  • Interpret γ/IFT primarily as a controlled trend metric (same temperature, same formulation window), and only trust changes when pendant-drop fit QC and inputs (temperature/density) are under control.
Read our USP page

Now It’s Your Turn

We hope this guide showed you how to apply surface science in the Pharmaceutical industry.

Now we’d like to turn it over to you: 

  • What’s the #1 real-world application from this post that you want to try first?
  • Perhaps we missed a relevant industry standard.
  • Or maybe you have a question about something you read.

Feel free to leave a comment below—we’d love to hear from you.

Frequently asked questions

Which surface measurement should a pharmaceutical lab start with?

Start with the failure you are trying to prevent. Use surface tension for solutions, inhaled products and spray drying feeds, and interfacial tension for emulsions and lipid systems. Use contact angle for tablets, device surfaces and cleaned equipment, and surface free energy for coatings. Our surface tension and contact angle guides explain each method.

What is USP ⟨1243⟩ and does it apply to my lab?

USP ⟨1243⟩ is a proposed chapter on wetting properties of pharmaceutical systems. It covers contact angle on solid dosage forms and surface or interfacial tension of liquids. It is not yet an enforceable requirement. The Dropometer uses the sessile drop and pendant drop methods and can supply that data, but it does not replace compendial requirements.

How is the critical micelle concentration found by surface tension?

Prepare a dilution series in the product medium, measure surface tension at each level, and plot it against the log of concentration. The CMC is the breakpoint where the steep slope meets the plateau. FDA 510(k) guidance for contact lens care products describes this approach. Control and record the medium, since results compare only within the same medium.

Can surface tension predict droplet size in inhalers or spray dryers?

It is one input, not a droplet size test. Surface tension, together with viscosity, shows when a formulation change is likely to shift droplet formation. For fast processes such as spraying, dynamic surface tension can matter more than the settled value. Confirm droplet or particle size with your own sizing method. See our inhalable medications page.

Can the Dropometer measure interfacial tension for lipid and emulsion systems?

Yes. A drop of one liquid is formed inside the second liquid, and the drop shape gives the interfacial tension. You need the density of both liquids. Harvard researchers used this pendant drop mode in a fluorinated oil emulsion study and a thesis on functional microcapsules. Lower tension alone did not stop droplets merging.

Can contact angle support cleaning verification?

It is a quick numeric check that an organic film is gone, not a substitute for your validated residue methods. Set limits from surfaces you know are clean and surfaces you know are soiled. Measure at fixed spots and a fixed time after the drop lands. Our surface cleanliness verification page covers the test plan.

How accurate is the Dropometer?

The drop shape method was validated against a KRUSS DSA100E in two peer reviewed papers, one in Review of Scientific Instruments and one in Colloids and Surfaces A. Published contact angle accuracy is 0.35 degrees. Automatic edge and baseline detection gives the same reading from the same image. See our validation papers.

Do published pharmaceutical and biomedical studies use the Dropometer?

Yes. Studies include an antibacterial resin coating for dental provisional crowns and a paper microfluidic glucose assay, where contact angle confirmed a laser step left the film hydrophobic. Spray drying and vesicle work appear in the case studies above. Browse every study on our client citations page.

Standards, evidence and resources

1. Industry standards
  • FDA 510(k) guidance: CMC by surface tension: Describes finding a surfactant's critical micelle concentration from surface tension across a dilution series for contact lens care cleaners, a workflow the Dropometer runs by pendant drop.
  • USP ⟨1243⟩: wetting of pharmaceutical systems: A proposed USP chapter, not yet enforceable, on contact angle of solid dosage forms and surface or interfacial tension of liquids, the two readings that show how formulations wet.
Use cases
  • Surface cleanliness verification: Water contact angle at fixed spots shows whether cleaning removed organic films from equipment, containers or components, as a quick numeric check beside validated residue tests.
  • Thin film and nanocoating surface characterization: Contact angles of several probe liquids give surface free energy of thin coatings, so formulation teams can see whether a film changed a substrate and how it ages.
  • CMC assessment and surfactant efficiency: Plot surface tension against log concentration to find the critical micelle concentration, so formulators set surfactant levels in solutions, suspensions and contact lens care products.
  • Inhalable medications: surface tension and droplet size: Surface tension, alongside viscosity and the device, shapes the droplets a nebulizer, inhaler or spray dryer makes, so tracking it flags excipient changes before slower sizing tests.
  • Lipid choice for vesicle manufacturing yield: Pendant drop interfacial tension of lipids at an oil and buffer interface helps rank lipid candidates for vesicle fabrication, where one published study found lower tension tracked with higher yield.
Case studies Client citations (our analysis of each paper) Use case collections Further resources