Towards the delivery of nano devices for functioning inside a living cell

Abstract

Shape Memory Materials (SMMs) are novel materials that have the ability to

recover their original shape even after severe deformations. There has been much

interest surrounding this type of materials, due to this Shape Memory Effect property.

Moreover, a wide variety of different breeds of SMM can be produced to suit

different applications.

In this report, the focus will be on Shape Memory Polymers (SMPs), a class of

SMM, to assess its viability to be applied to Biomedical technology. SMPs are a

cheaper alternative to its SMM counterparts, lightweight, and most importantly

biocompatible. Some are even biodegradable.

SMP wires are fabricated to obtain a coiled permanent shape, after which they

are straightened to a temporary shape by heating it to above its glass transition

temperature, Tg.

Two separate tests were carried out to test the recovery of the wires in toad

embryo. In the first test, the SMP wire was injected into the eggs immediately after

fabrication. Observations were then made at room temperature (25°C), and when the

egg sample was heated to different temperatures. Significant recovery was observed

at a temperature of 45°C

In the second test, the initial condition of the SMP wire was altered. It was

immersed in water for a day before insertion, and left in the eggs for a week before

the heating process. Slight recovery was found even before the heating process.

Furthermore, signs of significant recovery in this second test was evident at 37.5°C,

similar to the human body temperature.

This result is parallel to evidence of decreased Tg of SMPs when exposed to

moisture. This means that the SMP absorbed moisture, which changed its structure,

and lower energy is now required for the SMP to return to its original shape.