Cellulose based micromotors; rotation in a magnetic field

Cathal F. Prendergast ,  Adam W. McMahon ,  Aidan M. Doyle 

Advanced Materials Research Group, Manchester Metropolitan University, Chester St, Manchester M15GD, United Kingdom

Abstract

In the search for materials systems where molecular recognition is controllable, an exciting new phenomenon has been recorded on film under a cross-polarised optical microscope for the very first time. The synthesis of mesoporous silica by sol-gel mineralization of cellulose nanorod nematic suspensions has been studied in the past,1 but the reaction under a magnetic field has never been investigated. The presence of a thermal gradient in a fluid mixture induces a relative matter flow of the components and is known as the Ludwig-Soret effect.2 Cellulose microcrystals are helical in nature and align under a magnetic field.3 By applying a magnetic field in the region of 50 mT to the cellulose suspension, a novel spectacle is observed. The effect displayed is confined within a microdrop and is similar to a Tornado vortice as it rotates at high speeds moving erratically around the drop. Like a contained storm system, a combination of factors governs the resultant rotations. The helicity of the ionic cellulose, together with the reacting of the pre-hydrolysed silanol solution evolving gases is not enough to explain the high speed rotation, neither is the presence of a thermal gradient in the fluid. The aim of this paper is to report the phenomenon and to propose hypotheses as to what is actually occurring and harness this new discovery. With further research, this micro-tornado could be developed into a new generation of chemical motor.

1: E. Dujardin et al. J. Mater. Chem. 2003, 13, 696

2: R. Piazza et al. Phys. Rev. Lett. 2002, 88, 208302

3: J. F. Revol et al. Liq. Crystals 1994, 16, 127

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Presentation: Oral at E-MRS Fall Meeting 2006, Symposium J, by Cathal F. Prendergast
See On-line Journal of E-MRS Fall Meeting 2006

Submitted: 2006-05-14 13:38
Revised:   2009-06-07 00:44
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