Micro-Origami – Tiny Packages for Drug Delivery

Researchers at the University of Southern California have demonstrated a way to manufacture miniscule containers that could be used to deliver precise micro or even nano quantities of drugs.

A half-open micro-container (credit: ISI)
A half-open micro-container
(Credit: ISI)

An overdose of even ordinarily beneficial drugs can harm the body. Therefore, the new, tiny containers are designed in a way that will enable delivering precise micro – or even nano – quantities of drugs, leading to better, safer treatment.

The containers’ size is less than 30 micro-meters, approximately half the width of a human hair. According to Information Sciences Institute (ISI) Project Leader Peter Will, who is a research professor in the Viterbi School of Engineering, the new packages are manufactured in a two-step process: In the first step, flat patterns are created out of a sheet of polysilicon. These patterns are in essence origami-like. They resemble the fold-up shapes of paper pyramids, cubes, and other structures. Will’s origami, however, is 10,000 times smaller than the traditional Japanese art form. The basic patterns are etched into the polysilicon, and the area of the hinges is cleared to enable folding of the construct.

In the second step, the flat patterns are folded. The researchers electro-coat the blanks with permalloy to make them magnetic, leaving the hinge areas bare, to make sure the folding will occur only in those areas. Magnetic force is then applied to bend the hinges, followed by immersion of the tiny pieces in water. Capillary forces and pressure are generated by the water, and when the pieces dry off the final folding takes place, as the flaps closed over each other to form a closed shape.

The researches have shown that in a fashion similar to origami, the results can be varied by altering the sequence of folding, achieved by directing water at the polysilicon from different directions. By varying the drying time the researchers can also produce tighter seams, leading to packages that are closed more tightly , potentially allowing slower leakage of the drugs out of the containers.

Project Leader: Peter Will (credit: ISI)
Project leader: Peter Will (Credit: ISI)

The technique and results of this project were published in the Journal of Micromechanics and Microengineering. According to the authors, the new technique is extremely promising for mass production of micrometric packages, nicknamed voxels (volumetric pixels). The wide array of possible hinges and pattern geometries will allow the creation of varied functional shapes, as well as smaller voxels.

Aside from Will, the Voxel team includes Chemistry Professor Bruce Koel, former post-doctoral researcher Alejandro Bugacov, and former grad student (now graduate) Rob Gagler. Together the team folded a number of different shapes, including four – and five – sided pyramids, pentagonal ‘lotus’ shapes, and also simple square plates that folded over each other to create flat mini-envelopes.

Among the commercial applications of this new technology is drug delivery to the human body, by encapsulating the drug molecules inside the tiny voxels.

Other uses for micro- and nano-structures were covered in previous TFOT articles, including the release of insulin from an engineered nano-structure, and a micro-robot capable of moving inside blood vessels.

More information on the tiny voxels can be found on the ISI publishing page.

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