# gel

> solid jelly-like material that can have properties ranging from soft and weak to hard and tough. Gels are defined as a substantially dilute cross-linked system, which exhibits no flow when in the steady-state

**Wikidata**: [Q185744](https://www.wikidata.org/wiki/Q185744)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Gel)  
**Source**: https://4ort.xyz/entity/gel

## Summary
A gel is a solid, jelly-like material with properties ranging from soft and weak to hard and tough, defined as a cross-linked system that does not flow in a steady state. Gels are used in diverse applications, including medicine, materials science, and consumer products, due to their unique structural and functional versatility. Examples include hydrogels, aerogels, and silica gels, each tailored for specific uses.

## Key Facts
- Gels are cross-linked systems that exhibit no flow under steady-state conditions (definition).
- Subclasses include hydrogels (20 sitelinks), aerogels (59 sitelinks), and silica gels (45 sitelinks), reflecting their widespread relevance.
- Used as growth mediums for microorganisms or cells (34 sitelinks) and as dosage forms in medicinal products.
- Classified under chemical substances with identifiers such as MeSH Descriptor ID D005782 and IUPAC Gold Book ID G02600.
- Applications span medical (e.g., skin electrode gels), industrial (e.g., sol-gel processes), and consumer products (e.g., petroleum jelly).

## FAQs
### Q: What are common uses of gels?
A: Gels are used in medicine (e.g., drug delivery, wound care), materials science (e.g., aerogels for insulation), and consumer products (e.g., hair gels, lubricants like petroleum jelly).

### Q: How do gels differ from liquids?
A: Unlike liquids, gels do not flow in a steady state due to their cross-linked polymer networks, which maintain structural integrity.

### Q: What is a hydrogel?
A: A hydrogel is a network of hydrophilic polymer chains capable of retaining large amounts of water, used in applications like contact lenses and tissue engineering.

## Why It Matters
Gels are critical in multiple fields due to their adaptable properties. In medicine, they enable targeted drug delivery and wound healing; in materials science, aerogels provide ultra-lightweight insulation, while silica gels act as desiccants. Their non-flowing, cross-linked structure makes them indispensable for culturing cells, conducting electrophoresis (e.g., agarose gels), and developing flexible electronics. Gels bridge the gap between solids and liquids, offering tailored solutions to challenges ranging from energy efficiency to biomedical research.

## Notable For
- **Structural Versatility**: Gels exist in forms ranging from soft hydrogels to rigid aerogels, enabling diverse applications.
- **Non-Flowing State**: Their resistance to flow under steady conditions distinguishes them from liquids and semi-solids.
- **Biocompatibility**: Many gels (e.g., microgels, agarose gels) are biocompatible, making them vital in medical and biological research.
- **Industrial Relevance**: The sol-gel process is key to producing ceramics, glass, and coatings.

## Body
### Definition and Properties
- A gel is a cross-linked network of polymer chains or colloidal particles that traps a liquid, forming a semi-solid structure.
- **Key Characteristics**: 
  - No flow in steady state.
  - Properties range from soft (e.g., hydrogels) to hard (e.g., xerogels).
  - High porosity in forms like aerogels (up to 99.8% air).

### Subclasses and Applications
- **Hydrogels**: Hydrophilic networks used in contact lenses, drug delivery, and tissue engineering (20 sitelinks).
- **Aerogels**: Ultralight materials (99.8% air) for insulation, aerospace, and energy storage (59 sitelinks).
- **Silica Gels**: Porous silicon dioxide used as desiccants and catalyst supports (45 sitelinks).
- **Medical Uses**: Dosage forms (e.g., Gelclair), skin electrode gels, and wound dressings.
- **Research Tools**: Agarose gels for DNA separation, polyacrylamide gels for electrophoresis.

### Technical Specifications
- **Identifiers**: 
  - MeSH Descriptor ID: D005782.
  - IUPAC Gold Book ID: G02600.
  - UNSPSC Code: 12161801.
- **Classification**: Subclass of chemical substances (Wikidata: Q902163).
- **Related Processes**: Sol-gel process for material synthesis (25 sitelinks).

## References

1. Compendium of Chemical Terminology
2. Freebase Data Dumps. 2013
3. YSO-Wikidata mapping project
4. [Environment Ontology](https://raw.githubusercontent.com/INCATools/environments2wikidata/master/matches/curated-high-confidence-envo.tsv)
5. UMLS 2023
6. Quora
7. KBpedia
8. GF WordNet