This PDF file contains the front matter associated with SPIE Proceedings Volume 8107, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.
Liquid-Crystalline Elastomers (LCEs) are materials which combine the entropic properties of a crosslinked polymer melt
with the enthalpic properties of a liquid-crystalline state of order. LCEs show unique characteristics: visco-elasticity and
order at the same time in one system. The elastic and the viscous properties come from the crosslinking and friction of
the polymer chains, respectively, while the orientation comes from the mesophase which keeps the polymer backbone
aligned. LCEs behave as normal polymer networks or rubbers when no energy-storing mesophase is present. This state
of disorder can be induced by means of temperature or light. Thermally, the change in shape of LCEs can easily reach
300% when all the enthalpy stored by the mesophase is released and the crosslinked polymer chains are free to move and
adopt a random coil conformation. The light-induced local disorder can be achieved when shape-changing molecules are
incorporated in the LCE matrix. These compounds are able to absorb light, rearrange themselves in a new shape and
subsequently disturbing the mesophase. This results in the molecules that are keeping the order no longer being able to
sustain the retractive force of the polymer backbone, and the material contracts, exerting an actuating force. But how
does a light sensitive side-chain LCE elastomer behave? And a main-chain LCE? What about nematics or smectics? Is a
different kind of actuation, besides the common retractive force, possible? To answer these questions, new chemistry
needs to be developed, together with new physics to understand the systems, and new applications need to be created.
We characterize the monodomain nematic liquid crystal elastomers enriched with the carbon nanotubes (LCE-CNT
composites) with the purpose of general understanding the fundamentals of their mechanical actuation behavior when
illuminated by light and with the final objective to facilitate the design of photo-actuators based on LCE-CNTs. The
parameters like absorption spectra and absorption coefficients of the material as a function of CNTs concentration have
been studied. Temperature-induced three dimensional deformations were compared with the photo-induced deformations
monitored using SEM and conventional optical microscopy techniques, combined with thermal imaging done with the
Two acrylate monomers and two diacrylate crosslinkers containing a long spacer were synthesized and crosslinked
liquid-crystalline polymer (CLCP) films with different concentrations of azobenzene were prepared by
photopolymerization of the mixtures of the monomers and the crosslinkers. All the monomers, crosslinkers and
polymerizable mixtures exhibited LC phases in heating or/and cooling processes. Due to the relatively long spacer, the
obtained CLCP films exhibited a glass transition around 30 °C, which allows the CLCP films to undergo
photodeformations at room temperature. In addition, when the concentration of azobenzene decreased, the films bent
towards the light source with a faster speed and a larger photoinduced mechanical force.
Photomechanical actuation is preferred to electromechanical transduction because of some advantages including
wireless connection, a producing low noise, fast response etc. However, only few materials actually exhibit photoactuation.
Recently, nanotube-enriched elastomeric polymers have shown photo-actuating properties; the best results
were reported for liquid crystals elastomers. In the present paper we discuss photo-actuating behavior of new photoactuating
materials based on the commercial elastomer such as ethylene-vinylacetate copolymer (EVA) filled with
multiwalled carbon nanotubes (MWCNT) modified with novel, specific surfactant consisting of pyrenenyl and
cholesteryl groups. Orientation of MWCNT within the matrix was created by shear forces employing a special punch
and die system. Photo-actuation was characterized using AFM.
It is highly likely that future micro and nano-mechanical systems will be powered by light. However, the development of
such micro and nano-mechanical systems is still in its infancy. Potential advantages include remote triggering and
actuation, remote energy transmission, solar energy scavenging for useful work, and wavelength selectivity of actuation.
In recent years, carbon based nano-materials such as carbon nanotubes have shown highly interesting optical to
mechanical energy conversion. The development of optical to mechanical energy transducing mechanisms into practical
applications is still in its infancy. Only a few devices have been reported till date. This paper presents some of the recent
developments in the area of nanotube based photomechanical actuators with emphasis on micro and nanooptomechanical
systems. Devices namely micro-cantilevers for detection of free PSA, micro-grippers for manipulation
of small particles and micro-mirrors for light modulation have been developed that show both translational and
rotational actuation. Finally, integrating nanowires on these platforms could lead to the development of nanooptomechanical
systems. The future research of such systems and how they can play an integral part in electronics,
sensing and actuation by integrating nanotechnology with mechanics, optics and electronics is discussed.o
Over the last few years, several technologies have been adapted for use in tactile displays, such as thermo-pneumatic
actuators, piezoelectric polymers and dielectric elastomers. None of these approaches offers high-performance for
refreshable Braille display system (RBDS), due to considerations of weight, power efficiency and response speed.
Optical actuation offers an attractive alternative to solve limitations of current-art technologies, allowing
electromechanical decoupling, elimination of actuation circuits and remote controllability. Creating these opticallydriven
devices requires liquid crystal - carbon nanotube (LC-CNT) composites that show a reversible shape change in
response to an applied light. This work thus reports on novel opto-actuated Braille dots based on LC-CNT composite and
silicon mold microstamping. The manufacturing approach succeeds on producing blisters according to the Braille
standard for the visually impaired, by taking shear-aligned LC-CNT films and silicon stamps. For this application, we
need to define specifically-shaped structures. Some technologies have succeeded on elastomer microstructuring.
Nevertheless, they are not applicable for LC-CNT molding because they do not consider the stretching of the polymer
which is required for LC-CNT fabrication. Our process demonstrates that composites micro-molding and their 3-D
structuring is feasible by silicon-based stamping. Its work principle involves the mechanical stretching, allowing the LC
Photostructurable polymers, such as SU-8, have large potential impact on the field of MEMS/NEMS, allowing simple
fabrication of plastic MEMS/NEMS devices with nearly vertical sidewalls and high aspect ratios using standard
photolithographic procedures. Functional properties (as electrical conductivity or photoluminiscence) can be added to a
photostructurable polymer by doping the material with nanoparticles and/or nanocrystals. We present here the case in
which the resulting material presents opto-thermal properties if it is combined with an undoped polymer. From all the
different mechanisms for heating the structure, opto-thermal actuation is interesting from the point of view that it is
possible to obtain a mechanical energy transduction without requiring physical contact or proximity interaction, i.e.
devices can be moved merely by focusing light on it.
In microfluidics, valves and pumps that can combine specifications like precise flow control, provision of precise reagent
quantities, minimal sample carryover, and low-cost manufacture, while also being inherently compatible with
microfluidic system fabrication, are beyond the current state of the art. Actuators in micro-fluidics made using stimuliresponsive
materials are therefore of great interest as functional materials since actuation can be controlled without
physical contact, offering improvements in versatility during manifold fabrication, and control of the actuation
Herein we review the potential use of novel approaches to valving and pumping based on stimuli-responsive polymers
for controlling fluid movement within micro-fluidic channels. This has the potential to dramatically simplify the design,
fabrication and cost of microfluidic systems. In particular, stimuli-responsive gels incorporating ionic liquids (ILs)
produce so-called 'ionogels' that have many advantages over conventional materials. For example, through the tailoring
of chemical and physical properties of ILs, robustness, acid/ base character, viscosity and other critical operational
characteristics can be finely adjusted. Therefore, the characteristics of the ionogels can be tuned by simply changing the
IL and so the actuation behaviour of micro-valves made from these novel materials can be more closely controlled.
The motivation for this study is to reproduce processing conditions which lead to the formation of photo or photoinduced
thermal actuation, combined with inexpensive, environmentally friendly (easily degradable) materials.
Commercially available polymer, poly lactic acid (PLA), was used in our studies. PLA is a well know biodegradable
polymer naturally obtained from corn. PLA was received as a solid resin in pellet form and dissolved in 1:3
acetone/chloroform solutions, to achieve the proper electrospinning kinematic viscosity. Once in the liquid phase, the
material was mixed with commercially available multi-walled carbon nanotubes (MWCNTs) at varying concentrations
and dispersed by severe sonication. The mixtures was electrospun at room temperature using a home built electrospinning
apparatus capable of depositing randomly oriented fiber mats or oriented fibers onto different substrates, ranging from
oxidized silicon wafers, alumina squares or glass microscope slides. The fibers diameters and lengths are statistically
distributed following a log-normal distribution and the mean and dispersion are controlled by spinning parameters. Once
the fibers were electrospun, they were compositionally, morphologically and structurally characterized by thermal and
gravimetric analysis (TGA/DTA), rheology, imaging using a focused Ion Beam Scanning Electron Microscope (IBSEM),
and IR /Raman methodologies.
These studies can be used to explore PLA-MWCNTs mixtures suitability in applications such as super-capacitor
technology, which would enable us to pursue further research in this field, while focusing on improving the electro
spinning conditions so as to be able to better anticipate fiber morphology to generate a consistent regime of fibers.
The Boston-based National Braille Press has established a Center for Braille Innovation
(CBI), whose mission is to research and develop affordable braille literacy products. The
primary focus has been to facilitate the development of dramatically lower cost electronic
braille display devices, and the much-sought-after "Holy Braille" of a full-page electronic
Developing affordable new braille technologies is crucial to improving the extremely low
braille literacy rate (around 12%) of blind students.
Our CBI team is working to aid developers of braille technology by focusing attention
and resources on the development of the underlying braille actuator technologies. We
are also developing braille-related information resources to aid braille display
The CBI braille requirements summary (available through the NBP website
(http://www.nbp.org) is one of these resources. The braille specifications include braille
dot dimensions, spacing, displacement, lifting force, and response time requirements.
In addition, mentoring, helping to evaluate new braille display ideas, and openly sharing
braille display technology are all part of the activities of the NBP braille innovation team.
NBP has expanded the CBI project with domestic and international partners including
the China Braille Press, World Braille Foundation, National Federation of the Blind,
American Printing House for the Blind, American Foundation for the Blind, and many
university and research partners.
For over a decade, special emphasis has been placed in the convergence of different fields of science and
technology, in an effort to serve human needs by way of enhancing human capabilities. The convergence
of the Nano-Bio-Info-Cogni (NBIC) quartet will provide unique solutions to specific needs. This is the
case of, Nano-opto mechanical Systems (NOMS), presented as a solution to tactile perception, both for the
visually-impaired and for the general public. NOMS, based on photoactive polymer actuators and devices,
is a much sought-after technology. In this scheme, light sources promote mechanical actuation producing a
variety of nano-opto mechanical systems such as nano-grippers. In this paper, we will provide a series of
specifications that the NOMS team is targeting towards the development of a tactile display using
optically-activated smart materials. Indeed, tactile displays remain mainly mechanical, compromising
reload speeds and resolution which inhibit 3D tactile representation of web interfaces. We will also discuss
how advantageous NOMS tactile displays could be for the general public. Tactile processing based on
stimulation delivered through the NOMS tablet, will be tested using neuropsychology methods, in
particular event-related brain potentials. Additionally, the NOMS tablet will be instrumental to the
development of basic neuroscience research.
We present two models based on the theory of nonlinear elasticity of a photo-actuator consisting of a mixture
of a polymer matrix with carbon nanotubes. Both models are generalizations of the one proposed by Ahir
and Terentjev1 in which the actuation mechanism is modelled as a contraction of a given carbon nanotube in
response to an external stimuli. In the first model, a slight variation is introduced in the projection onto the axis
of the pre-strain. This new computation improves the result reported in1 for carbon nanotube photo-contraction
when a 10% pre-strain is applied. In our second model we use a nonlinear constitutive equation to describe the
mechanical response of the composite. We show that by a suitable selection of the parameters in the model,
consistent with the average constitutive parameters (Young modulus) reported in the literature, we can further
improve on the average carbon nanotube contraction for a 10% pre-strain threshold.
Optoactive polymer actuators and devices (OAPAD) are, undoubtedly, promising technologies. Analytical and finite
element models describing dynamics of photo-induced deformation in OAPADs have already been developed,
particularly for liquid crystal elastomers (LCE). Advanced materials like LCE - Carbon Nanotube (CNT) composites,
require a more complex physical analysis involving different coupled phenomena like photochemistry, photophysics and
chemomechanical coupling. The need for rigorous modeling of such complex physics as well as the imminent
implantation and development of ground-breaking practical OAPADs, demand a fast way to model the light-induced
deformation of the material. The purpose of this work is to build a finite element model serving as a bridge between
basic elastomer physics and device engineering and design. We take advantage of experimental actuation data to build an
empirical model describing the material deformation. The concept that sets the basis of the model is explained: the light
irradiation provokes the heating of the material mainly thanks to the absorption properties of the CNTs. Thus, we can
consider that CNTs behave as internal heat generators. Consequently, an opto-mechanical system based on LCE-CNT
can be evaluated and the mechanical response optimized.
In the current information age, scientists and educators are urged to disseminate scientific findings in a prompt manner for
increased public acceptance, later on, in the market place. Customer acceptance of highly novel technologies is an
education-driven effort that requires attention early-on during the stage of technology development. Prompt attention is
particularly needed in technologies where nanoparticles are employed, such as those being developed within the Nano-
Optical Mechanical Systems (NOMS) project. Another driving force to disseminate photoactuation is to generate interest
and curiosity amongst the K-12 population that could eventually lead to increased enrollment of students in the physical
sciences. In this paper, we present a work plan for the dissemination of photoactuation to society at large; from K-12 to
the general public. The work plan will be designed in accordance with the logic model, following indications of the
National Academy of Sciences, and will include a proposal for evaluating translational research following a process
Multiwall Carbon Nanotubes (MWCNTs) composites fabricated in the form of fibers with large surface areas were used
in the development of important technological applications such as photoactuators. MWCNT-polymer fibers can be
prepared with the simple and fast technique of electrospinning. The precursor for electrospinning was prepared by
adding dispersed MWCNTs to a polymeric solution of Poly(dimethylsiloxane) and Poly(methylmethacrylate) dissolved
in Tetrahydrofuran (THF) and Dimethylformamide (DMF). The dispersion of the carbon nanotubes in Sodium Dodecyl
Sulfate (SDS)/water is expected to enhance the photoactuation properties of the Polymer CNT Composites. The
dispersion of the MWCNTS in SDS and the properties of the precursor solution were analyzed using Scanning Electron
Microscopy (SEM), Ultraviolet-Visible Spectroscopy (UV-Vis), and X-Ray Diffraction (XRD) techniques.
Electrospun polymer-MWCNTs fibers were prepared using a precursor solution that consists of multiwall carbon
nanotubes (MWCNTs), Poly(dymethylsiloxane) and Poly(methylmethacrylate) in Tetrahydrofuran (THF) and
Dimethylformamide (DMF). Before adding them into the precursor, the MWCNTs were dispersed in Sodium Dodecyl
Sulfate (SDS) and water. We report evidence of UV photo-conduction and photo-actuation in electrospun
PDMS/PMMA-CNT composite fibers.