How to encapsulate tiny objects, with the option of removing the capsule later?

November 3, 2009 9:13 AM

Mad-scientist-filter: I need to encapsulate 1.5mm pellets in a thin, non-toxic, preferably natural material that could later be mechanically removed (example).

I would prefer that the capsule could come off cleanly. A difference from the example above is that the capsules would be removed from each pellet individually, one-at-a-time. (Why? Because I'm a mad scientist is why. Mwuhahahahaha.)

For the sake of visualization, let's say that I...
- am going to encapsulate nonpareils,
- have basic laboratory supplies,
- have any necessary safety equipment, and
- have $500 for other expenses.

What I'd actually like to encapsulate is similar enough to nonpareils that this would be an acceptable working model.

Have any thoughts on how I might do this? Wild speculation (that attempts to answer the question!) is entirely welcome. I'm brainstorming here-- or rather, storming your brains.

posted by zennie to grab bag (13 comments total)

How close does the encapsulation need to be to the tiny object? The smallest gelatin capsults I can quickly google for sale are size 4, which are 13.4 mm x 5 mm. Less than $20 for 1000.
posted by cobaltnine at 9:23 AM on November 3, 2009

It needs to be on or nearly on the object. Plus, despite the individual de-capsulation mentioned, having to put individual tiny objects into individual tiny capsules would not be so good.
posted by zennie at 9:30 AM on November 3, 2009

Plastisol coatings might work. The hardware store version is called Plastigrip. You dip metal tool handles in it and Voila! Total tool using comfort. Some versions are heat cured. The big issue would be whether or not the coating adheres to the object. A little WD40 or vegetable oil might solve this problem. You are pretty cryptic about other important parameters. Is this supposed to be edible?
There are many varieties of this stuff. It's frequently used to protect sharpened tools from corrosion until the happy new owner removes it.
posted by Carmody'sPrize at 9:47 AM on November 3, 2009

Could you encase them in some kind of substance that gels? In biology the workhorse material is agarose, which is a gelatinous substance extracted from seaweed. It's almost certainly non-toxic, since any practically any small organism is grown on agar plates

An advantage is also that the hardness of the gel can be controlled by changing the concentration of agar powder used. It also melts when heated, so you could remove the casing by heating or by rubbing it off mechanically.

Controlling the thickness of the coating might be difficult, however. I would imagine that you could force the "nonpareils" through a molten mixture of gel, and then out through a small pore filter on the other end. This would ensure that they have a relatively small coating, that would set very quickly once they were removed from heat.
posted by dubitoergosum at 10:10 AM on November 3, 2009

Since nonpareils are water-soluble, that makes a lot of thin coating applications more damaging (or absorbed, which might affect your non-toxic restriction) -- how about taking the process for wrapping regular-sized candies, and making it tiny? Unwrapping a double-twist-wrapped candy is easy with a machine - you take the ends and pull until it unwraps, or simply cut one of the twists to open one end.
posted by AzraelBrown at 10:12 AM on November 3, 2009

How about paraffin candle wax? Melts at 55 C.
posted by randomstriker at 10:25 AM on November 3, 2009

Oh and candle wax is easy to peel off mechanically, too. Just not very durable.
posted by randomstriker at 10:26 AM on November 3, 2009

Shapelock (aka Friendly Plastic). Solid at room temperatures, moldable gel when in very hot water. Available at hardware and arts and crafts stores.

Form it into a thin sheet, sprinkle your doodads on half of the sheet, fold sheet over to cover doodads. Cut with scissors / scalpel / knife / cookie cutter into encapsulated little doodads.

To remove, submerge encapsulated doodads into hot water until the plastic turns soft again, then mechanically separate, maybe using a scaled-down cherry pitter, or just squeeze the doodads between rollers to squirt them out.
posted by zippy at 10:59 AM on November 3, 2009

We used to encapsulate individual actinomycete spores by making a mixture of spores in molten alginate at a known concentration, then drop a known volume into a calcium chloride solution whereupon the alginate polymerizes and can be mechanically taken out of the solution (and placed into bacterial lawns by hand).

Don't know if the nonpareils will dissolve in the alginate, though.
posted by porpoise at 11:11 AM on November 3, 2009

In the book The One Straw Revolution, Fukuoka talks of coating seeds in clay. The process he uses is described in the book, I cannot remember it right now.
posted by bdc34 at 11:13 AM on November 3, 2009

There's always heat-shrink tubing. Fill tube with your tiny items, seal it by heating. If you seal one end before starting, you should be able to fill the entire tube with a funnel, then seal it off one short segment at a time by pinching it to empty a short section. Not sure if it will actually shrink enough to fully close off, you'd have to test.
posted by caution live frogs at 12:04 PM on November 3, 2009

Shellac is food safe, dissolves in alcohol rather than water and will form a hard surface. It's what they use to coat hard candies to stop them from sticking together. Also shellac flakes are cheap by the pound.

I don't know whether your mill would take the coating off though.
posted by Mitheral at 6:25 PM on November 3, 2009

Great answers here. Thank you! Sorry if my being cryptic was bothersome. I just wanted a wide variety of answers without broadcasting my exact idea.

I had no idea shellac was non-toxic.

AzraelBrown, your suggestion seems fantastically impractical, but I love it anyway for the image!
posted by zennie at 3:08 PM on November 4, 2009