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Séminaire de M.H. Godinho

A Cellulose Liquid Crystal Motor

A Cellulose Liquid Crystal Motor

Yong Geng1, Pedro Lúcio Almeida1,2, Susete Nogueira Fernandes1, Cheng Cheng3, Peter Palffy-Muhoray3*, Maria Helena Godinho1*

1 CENIMAT/I3N, Departamento de Ciência dos Materiais, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
2 Área Departamental de Física, ISEL/IPL, R. Conselheiro Emídio Navarro, 1, 1950-062 Lisboa, Portugal
3 Liquid Crystal Institute, Kent State University, Kent, Ohio 44242, USA
e-mails : ;

Cellulose is found in large quantities in nearly all plants and it seems an ideal material to mimic their micro and nano structures, iridescence and movements1, 2.
In this work we demonstrate moisture-mobile cellulosic soft materials that can convert chemical potential energy into mechanical work and exhibit three-dimensional movements upon moisture exposition. Solvent-dependent (chemical) applications of liquid crystalline networks shape change have been reported3. Changes in the orientation of constituents give rise to stresses and strains, which result in sample shape modification. Here we present for the first time a cellulosic soft motor driven by moisture. The motion is caused by a moisture-induced bend of a liquid crystal cellulosic film ; energy is provided by the chemical potential of the water vapour. The motor was built from a monodomain nematic film produced in the form of a circular loop. The loop passes over two wheels with horizontal axles 2. When humid air is present on one side of the film, near one of the wheels, with drier air elsewhere, rotation results. The motor runs so long as the difference in humidity is maintained. As the motor rotates, the film dries. The motor can be made to rotate faster if the ambient temperature is increased, or if the ambient humidity is reduced. Our cellulose motor extracts mechanical work from a difference in humidity.

We acknowledge support from the Portuguese Science and Technology Foundation through grants SFRH/BD/63574/2009, SFRH/BPD/78430/2011 to Y. Geng and S.N. Fernandes respectively, projects PTDC/CTM-POL/1484/2012, PTDC/FIS/110132/2009, PEst-C/CTM/LA0025/2011 (Strategic Project - LA 25 - 2011–2012) and from the U.S. National Science Foundation IIP 1114332.

[1] S.N Fernandes, Y. Geng, S. Vignolini, S. Glover, J. Beverley, A.C. Trindade, J.P. Canejo, P.L. Almeida, P. Brogueira, M.H. Godinho, “Structural Color and Iridescence in Transparent Sheared Cellulosic Films”, Macromolecular Chemistry and Physics 214(1), 25 (2013).

[2] Y. Geng, P.L. Almeida, S.N. Fernandes, C. Cheng, P. Palffy-Muhoray, M.H. Godinho, “A cellulose liquid crystal motor : a steam engine of the second kind”, Sci. Rep. 3, 1028 (2013).

[3] C. Ohm, E.-K Fleischmann, I. Kraus, C. Serra, R. Zentel, “Control of the properties of micrometer-sized actuators from liquid crystalline elastomers prepared in a microfluidic setup” Adv. Funct. Mater. 20(24), 4314–4322 (2010).