Start
Jun 15, 2011 - 00:30
End
Jun 15, 2011 - 11:30
Venue
Dept Library (Skype)
Event Type
Speaker
Dr Pratyush Dayal Department of Chemical and Petroleum Engineering University of Pittsburgh
Title
Modeling active self-oscillating gels that follow complex paths
Replicating “life-like” characteristics in man-made systems is a great challenge in science and engineering. Through the careful integration of soft materials and chemistry researchers have recently devised chemo-responsive polymer gels that autonomously oscillate in the absence of any external stimuli. The soft polymeric material of the gel allows it to bend stretch and change its shape in a manner analogous to living creatures. The chemistry on the other hand makes these gels self-powered by virtue of the oscillatory Belousov-Zhabotinsky (BZ) chemical reaction. Driven by the periodic oxidation and reduction of the ruthenium (Ru) catalyst which is grafted to the polymer network these BZ gels swell and de-swell and thereby transduce chemical energy into mechanical response. The BZ reaction however is photo-sensitive with light of a certain wavelength suppressing the oscillations within the gel. We demonstrate that the interplay between the chemo-responsive gels and the photosensitive reaction can cause mm sized BZ gels to exhibit autonomous directed motion or reorientation away from the light. Through the use of our recently developed three-dimensional gel lattice spring model we show that these synthetic BZ “worms” display a fundamental biomimetic behavior: movement away from an adverse environmental condition which in the context of the BZ reaction is the presence of light. Furthermore we exploit this property to control the self-sustained motion of macroscopic BZ gel “worms”. By tailoring the arrangement of illuminated and non-illuminated regions we direct the movement of these worms along complex paths guiding them to bend reorient and turn. In particular these gels can make both 900 and U-turns. Moreover the path and the direction of the gel’s motion can be dynamically and remotely reconfigured (as opposed to being fixed for example by a pattern on an underlying surface). We also perform stability analysis to establish broad guidelines that would yield the desired motion of the gel. Our findings can be utilized to design intelligent autonomously moving “soft robots” that can be reprogrammed “on demand” to move to a specific target location and to remain at this location for a chosen period of time.