Contents

Biotechnology Industry
The Practical Guide to Surface Science (2026)

fabiol-lisi
Written by
Dr Fabio Lisi
PhD in Chemistry from University of Melbourne. Postdoctoral Fellow University of New South Wales. Assistant Professor at University of Tokyo  
Guest Author
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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
fabiol-lisi
Written By

Dr Fabio Lisi

Guest Author

PhD in Chemistry from University of Melbourne. Postdoctoral Fellow University of New South Wales. Assistant Professor at University of Tokyo

 

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 Biotechnology Industry.

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

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

Let’s dive right in.

Biotechnology

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 biotech teams use contact angle, surface free energy, surface and interfacial tension on coatings, hydrogels, lipid formulations, sensors and process surfaces. Each measurement is tied to a real lab problem, a standard and published client work.
Key insights: In a 2025 Harvard study of asymmetric lipid vesicles, the authors observed higher vesicle yield at lower interfacial tension between buffer and lipid in oil. In a University of Toronto study, polyserotonin coatings lowered the water contact angle of glass by over 15 degrees. Contact angle shows that a surface changed; cell and protein response still needs its own assay.
Business value: Ranking lipids or coatings by a quick surface reading means fewer full fabrication runs and cell assays spent on weak candidates. One portable kit fits a shared facility, as at Harvard, where several labs use the same instrument.
Standards to follow: ASTM D1331 covers surface and interfacial tension of solutions by ring and plate methods, and pendant drop gives the same quantity by a different method. ASTM D7334 describes the advancing contact angle of water on coatings and films. Cite the edition your quality system uses.
Bottom line: Use interfacial tension to screen lipid and emulsion formulations, and contact angle to check every coating step. Start with the step that limits your yield, then book a 15 minute demo to try it on your own samples.

Chapter 1: Introduction

In biotechnology, many failed runs start at an interface. A lipid formulation that gives few vesicles wastes a fabrication run. A biomaterial coating that did not change the surface as planned gives misleading cell results.

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

The Dropometer contact angle and interfacial tension 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 Biotechnology 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 Biotechnology industry, several case studies exemplify the advantages of conducting surface property measurements.

Buffer Components Incorporate into the Framework of Polyserotonin Nanoparticles and Films During Synthesis

This study evaluates how buffer choice during serotonin polymerization influences the physicochemical properties of polyserotonin nanoparticles (PSeNP) and polyserotonin films, which are bioinspired materials with potential biomedical and coating applications. The authors demonstrate that buffer molecules can become incorporated into the forming polyserotonin matrix, supported by experimental surface/chemical analyses and density functional theory calculations. While nanoparticle elasticity remains similar across buffer systems, polyserotonin films show buffer-dependent differences in nanoscale surface properties, consistent with solvent/buffer effects on surface functional groups. Overall, the work provides guidance for selecting synthesis conditions to rationally tailor polyserotonin material properties toward specific applications.

Role of the Droplet Lab Goniometer

The Droplet Lab goniometer (cited in the paper as “Droplet Smart Tech, Markham, ON, Canada”) was used to measure static contact angles on polyserotonin-coated glass films using 20 µL droplets of milli-Q water, glycerol, and diiodomethane (Materials & Methods, Section 2.2, page 3). Those contact angle measurements were then used to calculate surface energy via the Owens-Wendt-Rabel-Kaelbel (OWRK) model, enabling quantitative comparison of buffer-dependent film wettability and surface energetics (Results/Discussion, Section 3.4, pages 7-8; Supplementary Figure S5 and Table S1 are referenced for the contact angle and surface energy data).

Key Findings

  • Buffer components can incorporate into polyserotonin frameworks during synthesis (evidence supported by chemical/surface characterization and DFT).
  • Nanoparticle size distribution depends on buffer choice (e.g., Tris produced the most uniform size distribution; other buffers yielded broader distributions).
  • Nanoparticle stiffness (apparent Young’s modulus) showed no significant dependence on buffer type when particles of comparable size were analyzed.
  • Polyserotonin films alter surface wetting: the film coating makes glass more hydrophilic, decreasing water contact angle by >15° and increasing surface energy from ~47 to ~61 mJ/m² (Section 3.4, pages 7-8).
  • The increase in surface energy for coated glass is driven more by the dispersive component than the polar component (Section 3.4, pages 7-8).
  • Buffer choice also affects film thickness and nanoscale surface interactions (e.g., Tris produced thinner films; HEPES produced thicker films per the referenced supplemental table).

Why It Matters

In biotechnology workflows such as biointerface coatings, nanoparticle-enabled delivery systems, and surface engineering for reduced fouling or controlled adsorption; small shifts in wettability, surface energy, and surface chemistry can change protein adsorption, cell interactions, and coating performance. This paper shows that buffer selection during synthesis is a practical “knob” to tune film surface properties (quantified via contact angle and surface energy) without materially changing nanoparticle stiffness, helping teams define synthesis specifications and QC targets that align with downstream biological performance.

Method Snapshot

Polyserotonin films on glass were evaluated using static contact angles: 20 µL droplets of water, glycerol, and diiodomethane were manually placed on the films and imaged (page 3, Section 2.2). Surface energy was calculated using the OWRK model, which uses the known surface tension components of the probe liquids (surface tension not measured directly in this study).

Data Note

Contact angle images of diiodomethane, glycerol, and water on PSe films formed on glass coverslips. A panel of alternating strips of PSe films formed on the glass coverslips on the right.

Figure

Citation (APA Format)

Jeon, K., Asuncion, J. A., Corbett, A. L., Yuan, T., Patel, M., Andoy, N. M. O., Kreis, C. T., Voznyy, O., & Sullan, R. M. A. (2022). Buffer components incorporate into the framework of polyserotonin nanoparticles and films during synthesis. Nanomaterials, 12(12), 2027. https://doi.org/10.3390/nano12122027

View Publication →

Sensor surfaces for fermentation and bioprocess monitoring

Sensors in fermentation and bioprocess work depend on how the culture medium wets their membranes and electrodes. Contact angle shows whether an electrode or barrier surface is consistent from one batch to the next.

Our laser inscribed graphene electrode QC page shows how contact angle tracks electrode batches. A Concordia University team measured the hydrophobic barrier in paper microfluidic glucose sensors. See also lateral flow wicking control.

Sensor surfaces for fermentation and bioprocess monitoring

Surface coatings for biomaterials

Coatings on biomaterials change how cells, proteins and bacteria meet the surface. Water contact angle before and after coating confirms the change, and surface free energy splits it into parts.

A University of Toronto team measured polyserotonin films on glass with three probe liquids. Universidad Católica de Temuco measured graphene oxide and PEI coatings for antimicrobial peptides. Researchers also measured bio adhesive hydrogels for muscle regeneration.

Surface coatings for biomaterials

Nanoscale vesicles for targeted delivery

Lipid vesicles that carry mRNA or proteins are often made by emulsion methods, where yield is hard to predict. Interfacial tension between buffer and each lipid in oil gives a quick way to rank lipid choices.

A Harvard team measured this by pendant drop in its study of asymmetric vesicles for mRNA and protein delivery, using the Harvard shared facility Dropometer. The screen covers the interface step only. Our lipid vesicle use case sets out the method.

Nanoscale vesicles for targeted delivery

Purification, emulsions and process cleaning

Purification and cleaning steps depend on surfactants, buffers and two phase systems behaving the same every time. Surface and interfacial tension of these solutions catch a changed lot before it reaches the process.

ASTM D1331 covers surface and interfacial tension of solutions by ring and plate methods. Pendant drop gives the same quantity by a different method, so state the method when you report. A Harvard team measured fluorinated oil and water interfacial tension in a study of complex emulsion droplets. For cleaned equipment, see surface cleanliness verification.

Purification, emulsions and process cleaning

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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 Biotechnology 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.

ASTM D1331, Surface & Interfacial Tension of Solutions (Du Noüy Ring / Wilhelmy Plate Force Methods)

What it is

ASTM D1331 is a method-defined standard for measuring surface tension and interfacial tension of liquids using force tensiometry, where a Du Noüy ring or Wilhelmy plate is pulled from a liquid or across an interface. Results may be called “ASTM D1331” only when generated using these ring/plate force methods (optical pendant-drop results are not D1331 as-written).

When to use it

Release/spec or customer-required reporting

Use when a customer, contract, or internal specification explicitly requires a value reported as “ASTM D1331” (ring/plate force tensiometry is required).

Reference method for method-bridging

Use as the periodic “truth” method to validate or calibrate faster internal screening methods (e.g., Dropometer pendant-drop) by building correlation bands against D1331 results.

In-scope / Out-of-scope

In scope
  • Surface tension of liquid formulations measured by Du Noüy ring or Wilhelmy plate force tensiometry.
  • Interfacial tension between two liquid phases (e.g., aqueous/organic, aqueous/oil) using ring/plate force tensiometry.
  • Comparative QC/R&D testing when the same geometry, corrections, and temperature control are used consistently.
  • Solutions that may include surfactants/additives (common in biotech formulations), provided handling, cleanliness, and equilibration are controlled and documented.
Out of scope
  • Optical pendant-drop (Young-Laplace) methods (e.g., Dropometer pendant drop) and any other non-force optical techniques.
  • Sessile-drop contact angle or solid-surface wettability/surface energy determinations.
  • Dynamic surface tension methods (e.g., maximum bubble pressure) unless your SOP explicitly defines how they relate (they are not D1331).
  • Labeling non-ring/plate results as “ASTM D1331” (method name is not interchangeable with the property name).

Minimum you must report (checklist)

  • Sample identity (formulation name, lot/batch, concentration of key excipients/surfactants, age/time since mixing).
  • Property measured: surface tension or interfacial tension; for interfacial, identify both phases.
  • Instrument + method geometry: Du Noüy ring or Wilhelmy plate; include ring/plate material and dimensions (as applicable).
  • Temperature and control method (setpoint, measured value, equilibration time).
  • Cleaning/conditioning protocol for ring/plate and sample vessel (and any acceptance check).
  • Replicate plan + statistics (n, mean/median, SD/IQR, outlier rule if used).
  • Correction/processing details used for force data (e.g., any correction factor approach and inputs required).
  • Deviations from ASTM D1331 or your internal SOP (and why).

Note: Dropometer (optical pendant-drop Young-Laplace) can measure the same property (surface/interfacial tension) but it does not comply with ASTM D1331 because D1331 requires ring/plate force tensiometry. Use pendant drop for internal trending/screening and reserve ring/plate for any result that must be labeled “ASTM D1331.”

How to interpret results (guardrails)

  • Treat γ as method-defined: do not compare pendant-drop γ and D1331 γ as interchangeable unless you have a validated bridge dataset.
  • Use correlation bands for QC decisions: build Green/Yellow/Red limits from paired measurements (Dropometer vs D1331) and re-verify periodically.
  • Watch repeatability as a signal: increased scatter often indicates contamination, poor cleaning, bubbles/particles, or unstable interfaces, investigate before releasing decisions.
  • Standardize time + temperature in biotech fluids: surfactant/protein systems can be time-dependent; control equilibration timing and report it consistently.
Read our ASTM D1331 page View the official ASTM D1331 Standard

Now It’s Your Turn

We hope this guide showed you how to apply surface science in the Biotechnology 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 biotech lab start with?

Start with the step that limits your results. Use interfacial tension for lipid, emulsion and two phase formulations. Use water contact angle for coatings, hydrogels and sensor surfaces. Use surface free energy, worked out from contact angles of two or more probe liquids, when you need its parts. Our contact angle and surface tension guides explain each method.

Which standards apply to surface tension and contact angle in biotech?

ASTM D1331 covers surface and interfacial tension of solutions by ring and plate methods. The Dropometer uses the pendant drop method, which gives the same quantity by a different route. ASTM D7334 describes the advancing contact angle of water on coatings and films, measured with a sessile drop. Check which method your protocol names.

Does lower interfacial tension give more lipid vesicles?

In one 2025 Harvard study, the authors observed higher asymmetric vesicle yield at lower interfacial tension between buffer and lipid in oil. Values ranged from 12 mN/m for POPS to 61.5 mN/m for DODMA. The mechanism was not tested. Treat tension as a ranking screen, then confirm yield in your own process. See the vesicle study analysis.

How do I measure contact angle on a hydrogel?

Swell the gel to a set state, blot off free water, and read the angle at a fixed short time after the drop lands. Hydrogels absorb water, so the angle changes with time. Report the drop volume and timing with every result. In one muscle regeneration study, GelTA hydrogels read around 50 to 70 degrees. See hydrogel wettability.

Does contact angle predict protein adsorption or cell response?

Not on its own. In a University of Saskatchewan study of carbon nitride films and protein adsorption, the authors found no film property that tracked protein binding. They used the Dropometer as a PTFE reference. Use contact angle to confirm the surface you made, and assays to measure biology.

Can I measure films made from biopolymers like chitosan and silk?

Yes. A Harvard undergraduate thesis measured water contact angle on chitosan and silk fibroin laminates with and without wax coatings. Both waxes raised the angle, but both stayed below 90 degrees. Keep films flat and dry before testing. See hydrophobic and hydrophilic surfaces.

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.

Standards, evidence and resources

1. Industry standards Use cases Case studies Client citations (our analysis of each paper) Use case collections Further resources