WEST LAFAYETTE, Ind. – Purdue University researchers have
developed a new type of pump for drug-delivery patches that might
use arrays of “microneedles” to deliver a wider range of
medications than now possible with conventional patches.
The current “transdermal” patches are limited to delivering
drugs that, like nicotine, are made of small hydrophobic molecules
that can be absorbed through the skin, said Babak Ziaie, a
professor of electrical and computer engineering and biomedical
“There are only a handful of drugs that currently can be
administered with patches,” he said. “Most new drugs are large
molecules that won’t go through the skin. And a lot of drugs, such
as those for treating cancer and autoimmune disorders, you can’t
take orally because they aren’t absorbed into the blood system
through the digestive tract.”
Patches that used arrays of tiny microneedles could deliver a
multitude of drugs, and the needles do not cause pain because they
barely penetrate the skin, he said.
“It’s like a bandage – you would use it and discard,” Ziaie
The patches require a pump to push the drugs through the narrow
needles, which have a diameter of about 20 microns, or roughly
one-fourth as wide as a human hair. However, pumps on the market
are too complex for patches, he said.
“We have developed a simple pump that’s activated by touch from
the heat of your finger and requires no battery,” Ziaie said.
The pump contains a liquid that boils at body temperature so
that the heat from a finger’s touch causes it to rapidly turn to a
vapor, exerting enough pressure to force drugs through the
“It takes 20 to 30 seconds,” Ziaie said.
The liquid is contained in a pouch separated from the drug by a
thin membrane made of a rubberlike polymer, called
polydimethylsiloxane, which is used as diaphragms in pumps.
Research findings are detailed in a paper being presented during
the 14th International Conference on Miniaturized Systems for
Chemistry and Life Sciences on Oct. 3-7 at University of Groningen
in The Netherlands. The paper was written by electrical and
computer engineering doctoral students Charilaos Mousoulis and
Manuel Ochoa and Ziaie.
Researchers have filed an application for a provisional patent
on the device.
Ziaie has tested prototypes with liquids called fluorocarbons,
which are used as refrigerants and also in semiconductor
“You need a relatively large force, a few pounds per square
inch, to push medications through the microneedles and into the
skin,” Ziaie said. “It’s very difficult to find a miniature pump
that can provide that much force.”
Findings indicate prototypes using the fluorocarbon HFE-7000
exerted 4.87 psi and another fluorocarbon, FC-3284, exerted 2.24