In both color cosmetics and skincare formulations, the emulsification system determines a range of critical performance attributes, including stability, skin feel, and active delivery capacity. Conventional O/W and W/O emulsification methods rely on surfactants to build an oil–water interfacial film and on mechanical energy to achieve uniform phase dispersion. These approaches are mature, reliable, and broadly applicable, and they remain the most widely used foundational emulsification pathways in the cosmetics industry.
As market demand continues to rise for low viscosity, high stability, and efficient encapsulation of active ingredients, more precise control over emulsion microstructure is required. In this context, D-phase emulsification technology, based on an "interfacial pre-construction" mechanism, offers an alternative approach by forming a denser interfacial film, enabling the preparation of emulsions with smaller particle size, narrower size distribution, and superior stability.
D-phase emulsification (DPE), also known as surfactant (D)-phase emulsification, achieves stable dispersion of the oil phase as extremely fine droplets within a continuous aqueous phase through precise control of the emulsification process, producing nanoemulsions with particle sizes ranging from 20 to 500 nm. This low-energy method enables the development of low-surfactant nanoemulsion systems that contain no organic solvents other than polyols [1–4]. Moreover, like other conventional low-energy emulsification approaches, it is suitable for large-scale industrial production without the need for specialized mechanical equipment, offering broad application potential in the pharmaceutical, cosmetics, and food industries [1,2].
This article begins with the formation mechanism of D-phase emulsification and systematically discusses its technical advantages, specific applications in the cosmetics field, and process advancements, aiming to provide a reliable technical blueprint for industry innovation.
1. Mechanism of D-Phase Emulsification
D-phase emulsification is essentially an intelligent emulsification control strategy based on a "pre-construction followed by dilution" concept. As illustrated in Figure 1, the core of this process lies in first dispersing emulsifiers in polyols to form an isotropic and homogeneous emulsifier-continuous phase (the D phase). The oil phase is then dispersed into the D phase, generating a gel-like O/D intermediate in which oil droplets are encapsulated by the D phase. Finally, the system is diluted by the gradual addition of water, yielding a finely structured O/W nanoemulsion [1–3].
Emulsions prepared by this method feature small droplet size, narrow size distribution, and large specific surface area, effectively suppressing droplet coalescence and Ostwald ripening. As a result, the system exhibits excellent physical stability and long-term storage performance [2]. The detailed preparation process is shown in Figure 1.
(1) D-phase formation: Nonionic surfactants are fully dispersed in a polyol solution to form an isotropic D phase.
(2) O/D gel formation: Under stirring, the oil phase is slowly added dropwise into the D phase to form an O/D gel, during which the system viscosity increases significantly. Care must be taken to control the oil addition rate, which should not be too rapid.
(3) Dilution and emulsification: The remaining aqueous phase is gradually added under homogeneous stirring, inducing phase inversion of the D phase into an O/W emulsion. During this step, the dilution rate and temperature must be carefully controlled to prevent droplet aggregation.
Optical Characteristics:
This material offers excellent light reflection and diffusion capabilities, delivering a refined, soft luminosity in both complexion and color cosmetic systems. It effectively enhances visual clarity and dimensionality without introducing harsh sparkle.
2. Advantages of D-Phase Emulsification
(1) Lower surfactant concentration
Unlike conventional emulsions, during the DPE process the oil phase is dispersed within the surfactant (D) phase. This allows large amounts of oil to be incorporated without requiring high surfactant levels or organic solvents other than polyols, enabling the formation of finely dispersed emulsions containing various oils [1,2]. As a result, nanoemulsions with high oil content can be prepared using a low concentration of a single hydrophilic surfactant [1,2]. Yukuyama et al. reported the preparation of an O/W nanoemulsion containing 40.0% (w/w) olive oil and only 2.0% (w/w) of a single hydrophilic surfactant, with droplet sizes of 20–30 nm, using the DPE process [1].
(2) No need for strict adjustment of hydrophilic–lipophilic balance (HLB)
In conventional phase inversion emulsification methods, such as the PIT and PIC techniques, an initially formed W/O emulsion must pass through an intermediate phase with low interfacial tension before being converted into an O/W nanoemulsion [5]. Formation of this intermediate phase requires complete solubilization of the oil phase within the surfactant-continuous phase to achieve sufficient oil solubilization, which is a key prerequisite for generating fine droplets and effective phase inversion [6]. This solubilization process is highly dependent on the system’s HLB value; therefore, traditional phase inversion methods typically require strict and time-consuming fine-tuning of HLB [2,7].
In contrast, in the DPE process the oil phase only needs to be dispersed—rather than dissolved—within the surfactant-continuous phase (D phase) to form a stable O/D intermediate. In this structure, oil acts as the dispersed phase and is encapsulated by an isotropic surfactant-continuous phase, resulting in extremely low interfacial tension [1,8]. Upon subsequent dilution with water, the O/D system can be smoothly converted into the final O/W emulsion with fine and uniform droplet size. Because this process does not rely on complete oil solubilization in the surfactant phase, strict control of HLB is unnecessary, significantly simplifying process development.
(3) No organic solvents required; polyols act as the fourth component in emulsification
In traditional high-oil systems, phase inversion methods for preparing O/W emulsions generally require large amounts of hydrophilic surfactants to induce phase transition and achieve the desired emulsification performance. However, as the concentration of hydrophilic surfactants increases, the solubility of the oil phase in the surfactant phase may decrease, necessitating even higher surfactant levels to form nanoemulsions [9]. In addition, such surfactants readily form structurally rigid hexagonal liquid crystalline phases in aqueous systems, which are inefficient at dispersing and accommodating large amounts of oil, thereby limiting the preparation of high–oil-content emulsions [8].
By contrast, the DPE process introduces polyols (such as glycerol), which promote the transformation of hexagonal liquid crystalline structures into an isotropic surfactant-continuous phase (D phase), effectively reducing the apparent hydrophilicity of the surfactants. Subsequent addition of the oil phase leads to the formation of a uniform O/D intermediate; at high oil contents, the system exhibits a translucent to transparent, highly viscous structure [8]. In this structure, oil serves as the dispersed phase, while the surfactant-continuous phase forms a nonporous interfacial layer, facilitating oil dispersion within the O/D phase and offering clear advantages over the rigid liquid crystalline phases formed in conventional phase inversion processes. Moreover, glycerol can increase the cloud point of nonionic surfactants, shifting their apparent hydrophilic–lipophilic balance toward lipophilicity, which helps regulate the system’s effective HLB and supports the formation of fine, stable emulsions via DPE [1,9].
Regarding the role of polyols in D-phase formation, differing viewpoints remain. Some researchers suggest that polyols inhibit liquid crystalline phase formation, whereas Kunieda et al. [10] proposed that the viscous, translucent structure may correspond to a lyotropic cubic liquid crystalline phase. However, Yukuyama et al. [1] confirmed through small-angle X-ray scattering analysis that no cubic liquid crystalline structure was formed in this system. Overall, the microstructure of this viscous system has not yet been fully elucidated and requires further investigation.
3. Application Examples of D-Phase Emulsification in Cosmetics
Under identical formulation conditions, how does the emulsification process itself influence the structure and performance of an emulsion system?
Using the same formulation, emulsions were prepared by conventional emulsification and by D-phase emulsification for comparison.
Figure 2 shows microscopic images of emulsions prepared by (a) conventional emulsification and (b) D-phase emulsification at 1000× magnification. Insets in the upper left corner display the corresponding macroscopic appearances of the emulsions. Particle size distribution profiles of emulsions prepared by (c) conventional emulsification and (d) D-phase emulsification are also presented.
As shown in Figure 2, emulsions obtained by conventional emulsification exhibit larger droplet sizes with a broader size distribution, with a D50 of approximately 420 nm and a D90 reaching about 600 nm. In contrast, emulsions prepared by D-phase emulsification display a finer and more uniform droplet size distribution, with a D50 of around 240 nm and a D90 of approximately 330 nm, indicating a markedly narrower distribution range. After centrifugation at 3,000 r/min for 30 minutes, the conventionally emulsified system shows obvious oil phase separation, reflecting poor stability (Figure 3). By comparison, no phase separation is observed in the D-phase emulsified system. In terms of sensory performance, the conventionally emulsified product feels relatively tacky, whereas the D-phase emulsified product delivers a noticeably lighter and fresher skin feel.
Figure 3. Stability comparison of emulsions prepared by two different emulsification methods
Based on this understanding, UNI-POWDER reengineered the system structure on the basis of D-phase emulsification, developing a more controllable, upgraded structural emulsification process that further optimizes fineness, stability, and compatibility of the system.
This technology has been applied to XSorb Chemical & Mineral Emulsified Water Slurry incorporating composite micropowders. Under identical formulation conditions, systematic comparisons were conducted with conventional emulsification and traditional D-phase emulsification processes. As shown in Figure 4, emulsions prepared using the innovative composite micropowder-structure emulsification technology (patent pending) exhibit lower viscosity, improved flowability, smaller particle size, and a more uniform particle size distribution. Overall system stability is also significantly enhanced.
Figure 4. Emulsions prepared by the upgraded D-phase emulsification method: (a) microscopic image (1000× magnification), (b) stability test, and (c) particle size distribution
4. Conclusion
D-phase emulsification is an innovative approach for preparing O/W nanoemulsions by dispersing surfactants in polyols. Compared with other low-energy emulsification technologies, this method offers multiple advantages: it requires lower surfactant concentrations, does not demand strict adherence to conventional hydrophilic–lipophilic balance (HLB) ratios, and uses no organic solvents other than polyols during processing.
Studies have shown that this process significantly reduces energy consumption. The resulting emulsions feature small droplet size, uniform size distribution, and high stability, demonstrating clear advantages in improving long-term product stability and optimizing sensory skin feel. In addition, D-phase emulsification exhibits good compatibility with oils of low polarity, low surface tension, and poor water solubility. With continued process optimization, this technology is expected to become a key driving force for high-end cosmetic innovation, supporting the goal of synergizing makeup performance with skin care benefits.
References
[1] M.N. Yukuyama, P.L.F. Oseliero, E.T.M. Kato, R. Lobënberg, C.L.P. de Oliveira, G. L.B. de Araujo, N.A. Bou-Chacra, High internal vegetable oil nanoemulsion: Dphase emulsification as a unique low energy process, Colloids Surfaces A Physicochem. Eng. Asp. 554 (2018) 296–305.
[2] H. Sagitani, Formation of Fine Emuisions by Surface Chemical Methods Focusing on the Mechanism of the Inversion Emulsification Method and the Surfactant (D) Phase Emulsification Method, J. Oleo Sci. 35 (1986) 198–2.
[3] W. Zhang, Y. Qin, S. Chang, H. Zhu, Q. Zhang. Influence of oil types on the formation and stability of nano-emulsions by D phase emulsification. J. Dispersion Sci. Technol. 42(2021), 1225–1232.
[4] Safaya M., Rotliwala Y. C. Nanoemulsions: A review on low energy formulation methods, characterization, applications and optimization technique. Materials Today: Proceedings. 2020, 27, 454-459.
[5] A. Murakami, K. Fukada, Y. Yamano, S. Gohtani, Effects of Sugars on the D Phase Emulsification of Triglyceride Using Polyoxyethylene Sorbitan Fatty Acid Ester, J. Oleo Sci. 54 (2005) 633–639.
[6] D. Morales, J.M. Gutiérrez, M.J. García-Celma, Y.C. Solans, A Study of the Relation between Bicontinuous Microemulsions and Oil/Water Nanoemulsion Formation, (2003) 7196–7200.
[7] H. Endoo, M., Sagitani, Preparation of Triglyceride O/W Emulsions by D Phase Emulsification, J. Oil Sci. 40 (1991) 133–139.
[8] H. Sagitani, Formation of O/W Emulsions By Surfactant Phase Emulsification and the Solution Behavior of Nonionic Surfactant System in the Emulsification Process, J. Dispers. Sci. Technol. 9 (1988) 115–129
[9] M. Sagitani, H., Nabeta, K., Nagai, A New Preparing Method for Fine O/W Emulsions by D Phase Emulsification and Their Application to Cosmetic Industry, J. Oleo Sci. 40 (1991) 988–994.
[10] H. Kunieda, M. Tanimoto, K. Shigeta, C. Rodriguez, Highly Concentrated Cubic-Phase Emulsions: Basic Study on D-Phase Emulsification using Isotropic Gels, J. Oleo Sci. 50 (2001) 633–639.
About UNI-POWDER
UNI-POWDER, a subsidiary of Co-fun Group, is a China-originated, globally oriented, one of the leading providers of high-quality cosmetic powder ingredient solutions. Since its founding in 2010, we have consistently upheld a customer-centric and market-driven approach, focusing on continuous innovation and research. We are committed to delivering one-stop cosmetic solutions from raw materials to formulations, covering UV filters, makeup, skincare, and functional ingredients, and customized powder services.
Guided by diligence, pragmatism, and a pursuit of excellence — our enduring “Powder Philosophy”— we aspire for every confident makeup look to benefit from UNI-POWDER.
Post time: May-19-2026