Thermo-elastic behavior of a polymeric layer bonded between rigid interfaces

Gih Keong Lau*, Johannes F.L. Goosen, Fred van Keulen

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


A highly expandable polymeric material have been combined with a stiff skeleton material to form a powerful design of thermal micro-actuators. The bond interfaces with the skeleton laterally restrain deformation of the polymer and consequently direct its volumetric expansion in the transverse direction. A complete lateral constraint at the infinite bond width could maximize the apparent thermal strain of the bonded polymer. However, it is not sure how much strain enhancement can be achieved using a finite bond width. To answer this, we resort to an approximate thermo-elastic model and solve it using the mean-pressure method. This model leads to closed-form solutions to the thermally induced strains and stresses in a bonded polymer layer between rigid interfaces. The closed-form solution shows that the apparent strain of a bonded layer depends on the aspect ratio of the bond width to the layer thickness, besides Poisson's ratio. Furthermore, it further shows that a bond width five times the thickness of the SU-8 epoxy layer is sufficient to attain 95% of the maximum apparent strain, which is obtained at the infinite width.

Original languageEnglish
Pages (from-to)5152-5164
Number of pages13
JournalInternational Journal of Solids and Structures
Issue number18-19
StatePublished - 1 Sep 2008


  • Actuators
  • Artificial muscle
  • MEMS
  • Polymers
  • Thermal effects in solids
  • Thermo-elasticity


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