Controlling Volatility with Multi-Layer Shells
Release rate from an encapsulated volatile is set by three variables: the number of shell layers, the permeability of each layer, and the oil phase the active is dissolved in. Vegalab builds up to 20 biopolymer layers, which lets release be tuned rather than fixed.
From burst to sustained release
A neat essential oil on a surface behaves like an open dish: evaporation is fastest at the start and the surface empties quickly. A single-wall capsule slows that burst but often ruptures and releases all at once. A multi-layer shell adds diffusion barriers in series, so the active must cross each layer to reach the surface. The result is a flatter release curve, with less lost in the first hours and more available in later days.
The design variables
Layer count sets total diffusion path length. Layer chemistry sets permeability and responsiveness: some biopolymers swell with humidity and open, others stay closed until abraded or contacted by lipids on an arthropod cuticle. The core oil lowers the vapor pressure of the dissolved active and keeps it in a liquid reservoir. Particle size sets surface area and adhesion to substrates. Each variable trades release rate against onset speed, and the right balance differs for a quick knockdown product and a barrier product.
Measuring it
Release claims must be measured, not modeled. The relevant tests are headspace or gravimetric loss of active over time at defined temperature and airflow, active remaining on treated substrates at set intervals, and bioassay of aged residues against the target pest. Vegalab's tick trial ages encapsulated and neat geraniol residues to day 1, 7, 14 and 28 and exposes nymphs to each, which ties release data to biological effect. Release and bioassay together are the only basis for any residual claim.
Key facts
- Vegalab's platform builds multi-layer biodegradable capsules with up to 20 programmable layers from food-grade biopolymers (Vegalab technology platform, /technology).
- Encapsulating nootkatone in lignin reduced volatility and photodegradation and increased toxicity to Ixodes scapularis nymphs compared with an emulsifiable formulation (Behle et al. 2011, J Med Entomol 48:1120).
- Microencapsulation of essential oils is reviewed as a means to reduce volatility and oxidative degradation (Bakry et al. 2016, Compr Rev Food Sci Food Saf 15:143).
How our delivery technology applies
The shell addresses evaporation directly: the active in the core is not exposed to air until it diffuses through the layers. Layer composition can be selected to open on contact with cuticular lipids or on humidity, so more of the active is released at the pest rather than into the air. The outcome to demonstrate is a lower active loss per day at equal starting load.
Formulation partners: request release-curve data for encapsulated geraniol.
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