The Nonlinear Optics Web Site

Photomechanical Architectures


Neural Networks

To understand the power of architectures, we first consider a neural network. A neuron is a pretty dumb basic unit whose output is a simple function of input. However, when neurons are connected together, as shown below, they can perform complex tasks.

Neural Network

Typically, one neuron is connected to a few others and interact with each other electrochemically.

Smart Threads

A smart thread is made by interconnecting many PODs. The diagram below shows a schematic representation of a smart thread made in a polymer optical fiber.

Smart threads

Unlike a neuron in the brain, each POD can communicate with all others directly using light rather than using the slower electrochemical neural process. Furthermore, each POD can be designed to act on a different wavelength of light, making it possible for a subset of PODs to communicate with other differently than with the rest of the collective.

In addition to performing logic operations using light, each POD acts as a sensor. Thus, information about stress being applied to one POD can be quickly transmitted to all other PODs. Furthermore, each POD acts as an actuator.

Thus, the collection of PODs on a smart thread each can sense stress or temperature, perform calculations, and provide actuation based on the information it receives from all of the other PODs. Such smart thread, when woven into a fabric, could yield an intelligence that is capable of morphing its shape. The technological possibilities go well beyond what electronics can do.

Photomechanical Swimmers

While the idea of photomechanics has been around for over a century, both scientific and technological progress has been hampered by the need for better materials.

In this decade, the group of Professor Palffy-Muhoray has developed elastomeric materials that have a more efficient photomechanical response, making interesting new device demonstrations possible.

The photograph below shows a tiny circular piece of an elastomeric material that has been stressed into the shape of a potato chip.[1]

Photomechanical Swimer

Photo and diagram courtesy of Professor Peter Palffy-Muhoray

By applying pulsed light to this structure, as diagramed above, the material can be made to flap in a way that results in a swimming motion. Indeed, Palffy-Muhoray and coworkers showed that such a structure, floating on water, swam away from a pulsed laser beam. Once the material enters a dark region, it stops swimming and remains in the dark. Thus, the materials behave like roaches in search of the protection of a shadow.

If such a material were made of a smart fabric, the functionality would be much more sophisticated. The examples here serve to illustrate the incredible potential of smart photomechanical technologies.


[1] M. Camacho-Lopez, H. Finkelmann, P. Palffy-Muhoray, and M. Shelley, "Fast liquid-crystal elastomer swims into the dark,"Nature Materials 3, 307 (2004).

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