Introduction

What is Microencapsulation ?

Application of Microencapsulation

Hot melt coating

Cyclodextrins

Extrusion

Emulsion Stabilisation

Jet break-up Processes

Super Critical Fluid technology

Complex Coacervation

Introduction

Processes for the production of spherical and monodisperse beads are of major interest to different industries, e.g. the pharmaceutical, chemical and food industries or in biotechnology. For such bead generation we will describe here 2 interesting technologies based on jet break-up principle :

  the vibration technology
  the jet-cutter technology

Technology

1- Vibration technology

This technology is based on an ancient principle (Lord Rayleigh, in the late 19th century) which shown that a laminar liquid jet breaks up into equally sized droplets by a superimposed vibration. The parameters are the frequency, the velocity of the jet and the nozzle diameter. They are easily and quickly determined in the light of a stroboscope to set-up an optimal vibration which can be reset in the future, making the process highly reproducible.

To guarantee the production of uniform beads or capsules and to avoid large size distributions due to coalescence effects during the flight, the droplets pass through an electrostatic field to be charged. As a result these droplets don’t hit each other during the flight and will be spread over a larger surface of the gelation bath thus resulting in monodisperse beads.

With the vibration technology it is possible to produce reproducibly capsules with equal diameter and spherical shape with a diameter within a range of 0,1 up to 3 mm.

If required the process can be scaled to flow rates up to 200 l/h ; and also under sterile conditions. This is particularly interesting for cell encapsulation.

2- JetCutter technology

The JetCutter is a simple technology for bead production that meets the requirement of producing monodisperse beads originating from low up to high viscous fluids with a high throughput.

The fluid is pressed at high velocity out of a nozzle as a solid jet. Directly underneath the nozzle the jet is cut into cylindrical segments by a rotating cutting tool made of small wires fixed in a holder. Driven by the surface tension, the cut cylindrical segments form spherical beads.

One of the major difference with the vibration technology is that only a mechanical cut and the subsequent bead shaping driven by the surface tension are responsible for bead generation, so the viscosity of the fluid has no direct influence on the bead formation itself.

Then, the JetCutter technology is capable to process fluids with viscosities up to several thousands mPa·s, i.e. viscosities somewhere between honey and tooth paste.

Note that the JetCutter technology is proprietory to geniaLab