As cosmetic formulations evolve beyond traditional emulsions and anhydrous systems, formulators increasingly seek structures that deliver stability, sensory control, and multifunctionality without relying on heavy emulsifier loads or synthetic polymers. Bigels have emerged as one of the most underutilized yet powerful answers to this challenge.
Bigels are semi-solid systems composed of two independently structured phases: a hydrogel and an oleogel. Unlike emulsions, where one phase is dispersed into another using surfactants, bigels retain distinct but interpenetrating networks. This architecture allows oil and water to coexist structurally rather than compete for dominance.
This article explains what defines a bigel system, how bigels differ from emulsions and gels, where they outperform conventional systems, and why they represent a distinct formulation category rather than a hybrid workaround.
What Is a Bigel?
A bigel is a biphasic gel system created by combining a hydrogel and an oleogel, each structured independently before integration. The resulting material exhibits properties of both phases while maintaining internal network integrity.
Importantly, bigels are not emulsions. They do not rely on surfactants to stabilize droplets. Instead, stability arises from the physical entanglement and spatial confinement of two gel networks.
Why Bigels Exist as a Separate Class of Systems
Traditional emulsions force oil and water into hierarchical roles: one continuous, one dispersed. This structure introduces interfacial instability, surfactant dependency, and sensitivity to electrolytes and pH.
Bigels avoid these constraints by allowing both oil and water phases to remain structurally autonomous. As a result, formulators gain:
- Reduced surfactant reliance
- Improved stability against phase separation
- Independent tuning of oil and water behavior
- Enhanced delivery flexibility
Structural Architecture of Bigels
Oleogel Network
The oleogel component provides oil immobilization, sensory cushion, and lipid-phase stability. Structuring agents form supramolecular or crystalline networks that restrict oil mobility without heavy wax loading.
Hydrogel Network
The hydrogel phase contributes hydration, cooling sensation, and water-soluble active delivery. Polymers or biopolymers create a three-dimensional aqueous network.
Interpenetrating Domains
When combined, these two gels interlock mechanically rather than chemically. This interpenetration creates a composite material with unique rheological and sensory properties.
Bigels vs Emulsions
| Parameter | Emulsions | Bigels |
|---|---|---|
| Stability mechanism | Surfactant-mediated | Network entanglement |
| Phase hierarchy | Continuous / dispersed | Co-dominant phases |
| Sensitivity to pH/electrolytes | High | Lower |
| Surfactant load | Required | Minimal or none |
Sensory Advantages of Bigel Systems
Bigels offer sensory profiles difficult to achieve with conventional systems. The hydrogel phase delivers immediate cooling and hydration, while the oleogel phase provides cushion, slip, and afterfeel.
Because these sensations occur sequentially rather than simultaneously, bigels often feel lighter and more controlled than emulsions with equivalent oil content.
Controlled Release and Active Delivery
Bigels enable compartmentalized delivery. Hydrophilic actives remain in the hydrogel phase, while lipophilic actives reside in the oleogel network.
This separation reduces incompatibility, protects sensitive actives, and allows independent release kinetics.
Stability and Migration Control
Oleogel structuring limits oil migration, while hydrogel confinement reduces water syneresis. Together, these effects enhance long-term physical stability.
Bigels often show improved resistance to temperature cycling compared to emulsions, particularly in low-surfactant formulations.
Where Bigels Excel
Bigels perform best in applications requiring both hydration and lipid delivery without heaviness.
- After-sun and soothing treatments
- Dermocosmetic repair products
- Scalp treatments
- Hybrid skincare-gel textures
Manufacturing and Processing Considerations
Bigels require careful process sequencing. Each gel must be fully formed before combination. Shear, temperature, and order of addition influence final structure.
As a result, bigels demand closer coordination between formulation design and manufacturing execution than standard emulsions.
Limitations of Bigel Systems
Bigels are not universal solutions. They may exhibit lower mechanical strength than wax-based systems and require precise processing control.
In addition, scale-up requires validation to ensure network integrity is maintained during production.
Regulatory and Claim Considerations
Bigels support claims based on delivery architecture and sensory experience rather than ingredient novelty. This aligns with increasing scrutiny of emulsifier-heavy systems.
Future Outlook
Bigels represent a shift toward architectural formulation design. As formulators move away from forced emulsification, bigels offer a structurally honest way to combine oil and water.
Key Takeaways
- Bigels combine independent hydrogel and oleogel networks
- They differ fundamentally from emulsions
- Sensory and stability benefits arise from structure
- They reduce reliance on surfactants
- Bigels enable precise active compartmentalization
