Techniques of Hydrogel Illustration

Hydrogels are 3 dimensional polymeric networks with high potential for many different applications, specifically in modern medicine. These structures are able to absorb and contain water up to 95% of their initial weight. Hydrogels can also retain different cargos such as drugs, macromolecules, and nanomaterials. Therefore, they are perfect candidates for drug delivery as well as biosensing, tissue engineering and many other applications. In this regard, accurate visualization of hydrogel structure is critical for scientists. A good illustration of the hydrogel is crucial for a better understanding of the behavior and the function of the hydrogel.

Hydrogel illustration methods can generally be divided into two categories: experimental illustration (based on microscopy) and digital (based on graphics).

Experimental hydrogel illustration

These methods involve direct imaging of the hydrogel samples in laboratory, using advanced microscopic methods.

1) Scanning electron microscopy (SEM)

SEM provides high-resolution images of the texture, surface, cross-linking density, and pore network of the hydrogel. Since hydrogels have a high water content, they normally require a dehydration process before SEM imaging. Freeze drying is a widely used technique that helps preserve the microstructure of the hydrogel network.

2) Atomic force microscopy (AFM)

AFM enables nanoscale surface scanning of the hydrogel. It is especially useful for analyzing local mechanical properties, nano-scale interactions, and surface roughness. Therefore, AFM is particularly valuable in soft materials and biointerfaces studies.

3) Confocal laser scanning microscopy (CLSM)

CLSM allows visualization of the hydrogels in their hydrated and natural state. This method benefits from fluorescent labeling and helps researchers to observe the porosity, molecular distribution, and dynamic changes in real time. CLSM is useful for studying drug release or cell encapsulation.

Digital modeling methods for hydrogel illustration

Digital visualization provides flexible and non-invasive ways for hydrogel illustration and simulation. These illustrative methods are widely used in scientific publications, modelling, and presentations. These methods are applicable as 3D illustration and 2D schematics.

Visual symbols and structural features

In scientific illustration, hydrogels are mainly represented using simplified symbols, depending on their scale, purpose, and application context. Common representations of hydrogels are as follows:

• Cubes:

Which symbolize solid-like hydrogel structures, and is often used in a tissue engineering context

• Cylinders:

These are used to illustrate hydrogel fibers, microneedles, or channels.

• Spheres or droplets:

Which represent microspheres or injectable hydrogels

Polymer network pattern within the hydrogel structure also needs simplifications in visualization. These chains are mainly shown with lines, meshes, or thread-like textures.

• Disordered and random formation of polymers inside the hydrogel represents isotropic hydrogels.

• Aligned fibers usually show a cross-linked network, which is often stimuli-responsive.

We can also have zoomed-in views to emphasize the porosity and exhibit the texture of the hydrogel.

Key research areas in which hydrogel illustration is widely applied

Drug delivery systems

Hydrogels are widely used in targeted and controlled drug release. A good illustration can show how the hydrogel is prepared, loaded with drugs, and releases the drug at specific sites within the body.

Environmental remediation and pollutant removal

Hydrogels are capable of absorbing pollutants from water and soil. Visual representation highlights the absorption procedure and the interaction of the hydrogel network with the pollutant.

Smart bandages, wound healing, and medical care

Advanced wound dressing is one of the most important applications of hydrogels, since they maintain moisture and can be tailored to exhibit antibacterial activity. Illustrative methods can help with showing how the hydrogel helps with wound closure and resists bacteria.

Biosensing and responsive hydrogel systems

Stimuli responsive hydrogels react to pH, temperature, or specific enzymes for biosensing applications. Diagrams and figures can help explain the sensing mechanism and signal appearance process.

Tissue engineering and regenerative medicine

Hydrogels serve as scaffolds in tissue engineering and can support cell growth. Illustrative methods can help show how cells interact with the hydrogel matrix and how the structure supports tissue formation.

Samples of hydrogels’ illustration on cover pages

Hydrogels are highly studied for 3D printing of scaffolds which will be used in a variety of applications, especially, tissue engineering. Scaffolds in tissue engineering are designed and prepared with similarity to the target tissue, so they can effectively mimic them in a biological environment. The sample cover below, shows 3D printing of a hydrogel for dental tissue engineering.