Functionalisation is one of the most important steps in biosensor development. Whether you're working with antibodies, aptamers, enzymes, ionophores, molecularly imprinted polymers (MIPs), or other sensing materials, the way you apply those materials to a screen printed electrode (SPE) can have a huge impact on sensor performance, reproducibility, cost, and scalability.
At first glance, applying a biological or chemical recognition element to an electrode may seem straightforward. However, the chosen functionalisation method can determine whether a sensor is suitable only for laboratory research or whether it can ultimately be manufactured at commercial scale.
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In this article, we compare three common approaches:
- Dip Coating
- Flooding
- Precision Deposition (Drop Casting)
and explain why precision deposition has become the preferred approach for commercial biosensor manufacturing.
What Is Screen Printed Electrode Functionalisation?
Functionalisation refers to modifying an electrode surface so that it acquires a specific sensing capability.
Examples include attaching:
- Antibodies for immunosensors
- Aptamers for highly selective target recognition
- Enzymes for enzymatic biosensors
- Ionophores for ion-selective electrodes
- Molecularly Imprinted Polymers (MIPs)
- Nanomaterials and catalytic materials
The objective is normally to place the functional material on the working electrode in a controlled and reproducible manner.
The challenge is determining the most practical way to achieve this.
Method 1: Dip Coating
Dip coating is perhaps the simplest functionalisation technique.
The process involves preparing a solution containing the desired reagent and then immersing the entire screen printed electrode into that solution.
While attractive because of its simplicity, dip coating has several significant disadvantages.
Excessive Reagent Consumption
Most biological recognition elements are expensive.
Antibodies, aptamers, and specialised enzymes can represent a substantial portion of development costs.
Dip coating typically requires millilitre-scale reagent volumes, most of which never participate in creating the sensing layer.
In many cases, the reagent cost alone makes dip coating impractical.
Poor Specificity
A biosensor should be carefully engineered, with material placed exactly where it is needed.
Dip coating exposes:
- The working electrode
- The reference electrode
- The counter electrode
- The front and back surfaces of the substrate
This means the reagent is being deposited in numerous locations where it provides no benefit.
For example, if your sensing chemistry only requires modification of the working electrode, why expose the reference and counter electrodes at all?
Risk of Contamination
One commonly observed problem is contamination from the reference electrode.
The solvents used during functionalisation may partially dissolve material from the reference electrode, particularly silver/silver chloride structures.
This dissolved material can then redeposit onto the working electrode, creating unexpected electrochemical behaviour and anomalous peaks during testing.
Poor Manufacturing Scalability
Perhaps the biggest issue is scalability.
Commercial biosensor manufacturers do not produce sensors by repeatedly dipping individual electrodes into beakers.
From a manufacturing perspective, dip coating is difficult to automate efficiently and can become expensive, slow, and inconsistent.
Method 2: Flooding
Flooding represents a slight improvement over full immersion.
In this method, a relatively large droplet, often 50 µL or more, is placed onto the front surface of the electrode.
The liquid spreads across the sensor, covering the working electrode while also contacting the reference and counter electrodes.
Reduced Waste But Still Inefficient
Flooding typically uses less reagent than dip coating, but it still consumes much more material than is actually required.
When expensive biological reagents are involved, those costs add up quickly.
Better Placement, But Not Precise Placement
Flooding avoids exposing the back side of the sensor, which is an improvement.
However, it still allows contact with areas that may not need modification, particularly the reference and counter electrodes.
Potential Reference Electrode Problems
Like dip coating, flooding can permit solvent interaction with the reference electrode.
This can result in silver chloride contamination and introduce unwanted responses into subsequent electrochemical measurements.
Semi-Scalable
Flooding can be scaled to a degree.
For example, sheets of screen printed electrodes may be processed together rather than individually.
However, flooding still lacks the precision and automation compatibility needed for high-volume commercial manufacturing.
Method 3: Precision Deposition (Drop Casting)
Precision deposition, often called drop casting, involves placing a carefully measured volume directly onto the working electrode.
Rather than using excessive reagent volumes, only the required quantity is dispensed.
For example, when using Zimmer & Peacock's best-selling Hyper Value 501 Carbon Electrode, approximately 2 to 3 µL is often sufficient to cover the working electrode.
Improved Reagent Utilisation
Using microlitre volumes dramatically reduces reagent consumption.
This is particularly valuable when working with:
- Antibodies
- Aptamers
- Enzymes
- Nanomaterials
- Custom synthetic receptors
Lower reagent consumption means lower development costs and lower manufacturing costs.
Greater Specificity
With precision deposition, the functional material is applied exactly where it is needed.
The working electrode receives the chemistry.
The reference and counter electrodes remain untouched.
This level of control improves sensor consistency and reduces unnecessary risks.
Better Reproducibility
Reproducibility is critical in both research and manufacturing.
Applying a defined volume to a defined location reduces variability between devices and improves overall sensor performance.
Designed for Automation
The greatest strength of precision deposition is scalability.
Commercial biosensor manufacturing routinely uses automated liquid handling and robotic dispensing systems that apply tiny volumes with exceptional consistency.
Manual pipetting in the laboratory effectively mirrors what a robotic system will later perform on a larger scale.
By adopting precision deposition early in development, researchers naturally move towards processes that are compatible with future manufacturing.
Thinking About Scale from Day One
A common mistake during sensor development is to optimise a process that cannot realistically be manufactured.
The question every biosensor developer should ask is:
How will I scale this process if the sensor succeeds?
Choosing precision deposition from the start can reduce development risks later and make technology transfer into manufacturing substantially easier.
Recommended Electrode Preparation
Before functionalisation, proper cleaning and rinsing can improve sensor consistency and reliability.
Whether your screen printed electrodes come from Zimmer & Peacock or another supplier, we recommend:
Cleaning Solution
Cleaning Solution
https://shop.zimmerpeacock.com/en-gb/products/cleaning-solution
Biosensor Rinse Solution
Biosensor Rinse Solution
https://shop.zimmerpeacock.com/en-gb/products/biosensor-rinse-solution
Recommended Screen Printed Electrode
For researchers looking to develop scalable biosensors, one of our most popular platforms is the:
Hyper Value 501 Carbon Electrode
Browse our full range of screen printed electrodes:
https://shop.zimmerpeacock.com/en-gb/collections/bare-electrodes
Learn more about biosensor development:
https://shop.zimmerpeacock.com/en-gb/pages/sensors
Explore solutions and accessories for SPE work:
https://shop.zimmerpeacock.com/en-gb/collections/solutions
Explore biosensor chemicals and reagents:
https://shop.zimmerpeacock.com/en-gb/collections/chemical-and-solutions
Conclusion
All three functionalisation methods can produce a working sensor.
However, they are not equal.
Dip coating consumes excessive reagent, lacks specificity, and scales poorly.
Flooding improves matters somewhat but still exposes unnecessary electrode structures and can introduce contamination risks.
Precision deposition (drop casting) provides:
✅ Lower reagent consumption
✅ Better control of chemistry placement
✅ Improved reproducibility
✅ Reduced contamination risk
✅ Compatibility with automated manufacturing
For developers serious about commercial biosensors, precision deposition is not simply a laboratory technique.
It is the pathway towards scalable, manufacturable sensor production.
Need Help?
If you would like support with biosensor development, screen printed electrodes, sensor functionalisation, or manufacturing scale-up, please get in touch:
