Programmable/Water Actuatable Shape Memory Polymer



W. M. Huang, B. Yang, and C. Li

CMMS, School of MPE

Nanyang Technological University, Singapore


Contact Dr WM Huang: Telephone: (65) 67904859; Fax: (65) 67911859; E-mail:



In recent years, shape memory polymers attract great interest for their enormous potential applications, in particular, in medical devices [1,2]. The most recent invention of biodegradable shape memory polymers opens a window for some more advanced ones [3]. The shape memory phenomenon in some polymers is a result of two structural features, one determining the permanent shape and the other having a thermal transition within a certain temperature range [4,5].


However, it is difficult to fabricate functionally gradient shape memory polymers, which have different properties, e.g. variable transformation temperature, from one segment to another. The main advantage of functionally gradient shape memory polymer, for instance with variable transformation temperature, is that the recovery of the polymer can be in a programmable manner instead of simultaneously everywhere. In addition, as shape memory polymers are non-conductive in nature, their actuation has to be triggered by external heat. Although conductive shape memory polymers can be produced by blending with conductive particles (one existing patent), the properties of shape memory polymers (i.e., bio-compatibility) may be changed.


It is a significant advantage if shape memory polymers are functionally gradient (i.e. with variable transformation temperature) and can be actuated by some other convenient means.


Novelty of the invention

We propose a novel way to fabricate functionally gradient shape memory polymers, which can be actuated by water. This technique provides an approach for recovery of shape memory polymers inside, e.g., human body, without any heating system and in a programmable manner following a prescribed sequence.


Advantages and improvements over existing methods, devices or materials

The proposed approach is convenient in fabrication and application.  To the best of our knowledge, this has not yet been mentioned anywhere else. It is based on our recent findings.


Technical description of the invention

The fundamental reason is the effect of moisture on the transformation temperature of shape memory polymers.


Water actuated SMP



Recovery of SMP in a programmable manner



Water actuated functionally gradient SMP


Commercial applications

The application of this invention should be enormous, in particular in medical devices as shape memory polymers are bio-compatible, very cheap and easy in fabrication as compared with others, e.g. shape memory alloys.


Retractable stent and self-tightened suture are potential ones at present.




[1] Wache, H.M., Tartakowska, D.J., Hentrich, A., Wagner, M.H., J. Mater. Sci: Mater. Medicine., 12, 2003, 109-112

[2] Metcalfe, A., Desfaits, A.-C., Salazkin, I., Yahia, L., Sokolowski, W.M., Raymond, J., Biomaterials, 24, 2003, 491-497

[3] Lendlein, A. Langer, R., Science, 296, 2002, 1673-1676

[4] Lee, B.S., Chun, B.C., Chung, Y.-C. Sul, K.I, Cho, J.W., Macromolecules, 34, 2001, 6431-6437

[5] Lendlein, A., Schmidt, A. M., Langer, R., PNAS, 98(3), 2001, 842-847