You are here
Cephalopod-inspired Design of Electro-mechano-chemically Responsive Elastomers for On-demand Fluorescent Patterning
Cephalopod-inspired Design of Electro-mechano-chemically Responsive Elastomers for On-demand Fluorescent Patterning
Qiming Wang, Gregory R. Gossweiler, Stephen L. Craig*, Xuanhe Zhao*
Cephalopods can display dazzling patterns of colors by selectively contracting muscles to reversibly activate chromatophores – pigment-containing cells under their skins. Inspired by this novel coloring strategy found in nature, we design an electro-mechano-chemically responsive elastomer system that can exhibit a wide variety of fluorescent patterns under the control of electric fields. We covalently couple a stretchable elastomer with mechanochromic molecules, which emit strong fluorescent signals if sufficiently deformed. We then use electric fields to induce various patterns of large deformation on the elastomer surface, which displays versatile fluorescent patterns including lines, circles and letters on demand. Theoretical models are further constructed to predict the electrically-induced fluorescent patterns and to guide the design of this class of elastomers and devices. The material and method open promising avenues for creating flexible devices in soft/wet environments that combine deformation, colorimetric and fluorescent response with topological and chemical changes in response to a single remote signal.
Corresponding email: zhaox@mit.edu, stephen.craig@duke.edu
Nature Communications, 5, 4899 (2014)
PDF, Supporting Information, Video 1, Video 2, Video 3, Video 4
This work has been reported by MIT Featured News, The Washington Post, Wall Street Journal, The Slate, Gizmodo, IFLScience and more
You may watch the video on Youtube: https://www.youtube.com/watch?v=kM-e2j8Equg
- Qiming Wang's blog
- Log in or register to post comments
- 13508 reads
Comments
Two quick questions
Dear Qiming,
First of all, congratulations to your publication in Nature Communications! A beautiful work! I just read though this morning and have the following simple questions:
1. On page 8 in the part of "electro-activation of EMCR elastomers", you give the definition of electric filed. I do not understand this. Would you please explain it a little bit?
2. In supporting information, you give the outline of linear stability analysis. Can you suggest me more references to fullly understand the details of this?
Thanks,
Jinxiong
Jinxiong, Thank you for your comments
Dear Jinxiong,
Thank you for your interest in our paper.
1. In this paper we define the applied electric field as the electric field in the EMCR film at the flat state. Considering E κ=Er κr and Φ=E(Hf+Hs)+ErHr, we can obtain the expression for the applied electric field on the second line of page 8.
2. For better understanding the linear stability analysis in the current paper, I would suggest the following two papers:
Qiming Wang, Xuanhe Zhao, Creasing-Wrinkling Transition in Elastomer Films under Electric Fields, Physical Review E, 88, 042403 (2013) Supporting Information, Video 1
Shenoy, Vijay, and Ashutosh Sharma. "Stability of a thin elastic film interacting with a contactor." Journal of the Mechanics and Physics of Solids 50.5 (2002): 1155-1173.
Best,
Qiming
Hi Qiming,
Hi Qiming,
Really cool combination of dielectric elastomers and mechanochemistry concepts.
First the mechanics commentary - nice use of the first invariant! I see you have the polymer mechanical behavior fit in your supplementary info. Have you tried to back calculate the polymer chain force associated with the fluorescence?
I noticed the fluorescence intensity dip at the start of mechanical loading which has also been seen in other spiropyran-linked elastomers. Do you believe that this is a thickness effect or do you have another proposed origin?
Questions about time - Does the fluorescence intensity depend at all on the rate of mechanical loading/rate of application of the electric field? How long does it take for the fluorescence to fade to near baseline after the removal of mechanical loading/electric field without the use of green light?
thanks,
Meredith
Reply to Meredith
Dear Meredith,
Thank you for your interest in our work.
(1) Yes, I have calculated the relationship between the polymer chain force and the fluorescence intensity. The chain force can be calculated by δ(free energy in a chain)/δ(chain length). The chain force affects the chemical kinetics by following Bell model. The chemical kinetics determines the concentration of the colored molecules, thus representing the fluorescence intensity.
(2) The fluorescence intensity-first invariant curves indeed follow a stagnant-increase trend (maybe decrease a little bit and then increase). You are correct: it is a thickness effect.
(3) Rate dependence – Yes, although we only consider a quasi-static loading in the current paper, we believe the fluorescence intensity will be affected by the loading rate. However, it will be challenging to capture this effect, because the chemical reaction is not instantaneous but takes time to reach equilibrium (from several seconds to one minute).
Without the green light, the fluorescence will fade to the baseline for around 1 hour. The green light can accelerate this process to 1-3 minutes.
Hope my answers have addressed your concerns. See you in the near future.
Best regards,
Qiming