Imagine working in an ultra-modern building like this one in Malaysia, next to a glass wall equipped with smart curtains that keep your workspace comfortably lit. This soon could be a reality.
A reversible photoactuator, a device that moves in response to light, has been created using polymer film and carbon nanotube bilayers. Carbon nanotubes have been used in actuators since 1999 due to their excellent heat and electrical conductivity. In this new application, the nanotubes create the movement in response to light, unlike polymer photo actuators that rely on photosensitive polymers.
A team of researchers from Lawrence Berkeley National Laboratory at the University of California, Berkeley, and Northwestern University in Evanston, Ill., has created smart curtains based on polymer and single-walled carbon nanotube bilayers. They offer fast (under 1 second), reversible actuation and wavelength-selective response. Light-responsive smart curtains potentially have many applications in modern architecture, maintaining energy and light efficiency. Here is how Sarah Yang describes it at UC Berkeley News Center:
A research team led by Ali Javey, associate professor of electrical engineering and computer sciences, layered carbon nanotubes — atom-thick rolls of carbon — onto a plastic polycarbonate membrane to create a material that moves quickly in response to light. Within fractions of a second, the nanotubes absorb light, convert it into heat and transfer the heat to the polycarbonate membrane’s surface. The plastic expands in response to the heat, while the nanotube layer does not, causing the two-layered material to bend.
The video shows two types of film actuators, with the opposite reaction to a light-darkness cycle. The movement of the bilayer films, created by the difference in the thermal properties of the polymer film and nanotubes, was highly reproducible even after 60,000 cycles. Published in Nature Communications, the work also describes a light-driven resonator, motor and oscillator, further advancing the exciting field of photoactuators:
Previously explored materials and structures do not simultaneously offer fast and wavelength-selective response, reversible actuation, low-cost fabrication and large deflection. Here, we demonstrate highly versatile photoactuators, oscillators and motors based on polymer/single-walled carbon nanotube bilayers that meet all the above requirements.
Another exciting “smart” development in this group is a flexible user-interactive sensor network, or electronic skin, which responds to touch by lighting up. Smart indeed!
Source: Photoactuators and motors based on carbon nanotubes with selective chirality distributions, X. Zhang et al., Nature Communications 5:2983, DOI:doi:10.1038/ncomms3983, Jan. 7, 2014
Source: Research Brief: Engineers create light-activated ‘curtains,’ Sarah Yang, UC Berkeley News Center, Jan. 9, 2014
Source: Paper-thin e-skin responds to touch, holds promise for sensory robotics and interactive environments, Sarah Yang, UC Berkeley News Center, July 21, 2013
Image: Glass Trapezium by Fizal’s Photography
Video: Smart Curtains, ucberkeleycampuslife, youtube