Lorna Parashin Portfolio 2009

8/14/2019 Lorna Parashin Portfolio 2009

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JCE Classroom Activit

Colors in Liquid CrystalsGeorge Lisensky and Elizabeth Boatman Beloit College, Beloit, WI 53511

In this Activity students investigate the relationship between temperature and composition and the reftransmitted colors of a common nanoscale material, the cholesteric liquid crystal.

BackgroundCholesteric-phase liquid crystals contain molecules aligned inlayers (1) rotated with respect to one another (Figure 1, p 1360B).The rotation angle from one layer to the next increases with tem-perature, so the distance between layers with the same orienta-tion, called the pitch, decreases with temperature. The helicalstructure selectively diffracts light (2) according to the Bragg con-

dition modified by Snells Law(3), = np(1cos2/n2)1/2 where is the reflected wavelength, n is the mean refractive index (~1.5for these materials),p is the pitch, and is the angle with respectto the surface. Squeezing these soft materials changes the spacingbetween molecules, changing the reflected color.

Figure 3 shows the wavelength of reflected light as a s ample coolsthrough its liquid crystal phase (4). The colors span the visiblespectrum from blue to red.

Integrating the Activity into Your CurriculumThis Activity is suitable for exploring relationships between color, wavelength, reflection, and transmissiontrates how temperature changes the Bragg reflection wavelength in liquid crystals. This Activity can also explore the relationship between melting point and crystal packing. (See Question 3).

About the ActivityAhead of time combine 0.65 g cholesteryl oleyl carbonate (Aldrich 151157), 0.25 g cholesteryl pelargonatC78801), and 0.10 g cholesteryl benzoate (Aldrich C75802) in a glass vial with a screw-on lid. Melt the cona hair drier to form a liquid crystal mixture with a phase transition just above ambient temperature (6) tdivided amongst 2030 students to spread between two layers of contact paper to make a liquid crystal sReplacing some of the cholesteryl oleyl carbonate with cholesteryl pelargonate (keeping a combined mass raises the transition temperature as the molecules pack together better. For example, reversing the massestransition temperature by 20 C (7). Cholesteric liquid crystals can degrade when exposed to moisture orstored in a sealed container the mixture can be prepar ed months in advance. Use these materials with normaprecautions. Do not inhale solids; avoid contact with skin, eyes, or clothing. Wash thoroughly after handl

Answers to Questions1. Reflected and transmitted colors are opposites (e.g., purple/yellow). The color changes with angle. If y

red perpendicular to the surface (l= 630 nm) you would observe yellow 45 from the surface (l= 5

2. The colors change through red, orange, yellow, green, blue to purple as the samples temperature incorder of decreasing wavelength corresponds to decreasing pitch.

3. The shape of cis-unsaturated fatty acids such as cholesteryl oleyl carbonate (see structure in this issOnlineW) makes them less able to pack together; the melting temperature of the liquid crystal mixture dthe percent composition of cholesteryl oleyl carbonate increases.

References, Additional Related Activities, and Demonstrations1. Liberko, C. A.; Shearer, J.J. Chem. Educ.2000,77, 12041205; supplemental material suggests the fish analogy t

liquid crystals (http://www.jce.divched.org/Journal/Issues/2000/Sep/abs1204.html).

2. Palffy-Muhoray, P. Nature1998,391, 745746.

3. Nassau, K. The Physics and Chemistry of Color; Wiley: New York, 1983; pp 430431.

4. Reflectance data were obtained using an Ocean Optics USB 2000 spectrometer equipped with a fiber optic oriendicular to a 0.15-mm thick sample mounted between two microscope slides with cover slips as spacers over a black and illuminated with a white LED light source.

5. Pindak, R. S.; Huang, C. C., Ho, J. T. Phys. Rev. Lett.1974,32, 4346.

6. This procedure assumes that room temperature will be below 25C and thus below the liquid crystal phase transittemperature is warmer, the composition should be adjusted to give a higher transition temperature.

7. Cholesteryl Ester Liquid Crystals. http://www.mrsec.wisc.edu/Edetc/nanolab/LC_prep/index.html(accessed June 200

We thank the National Science Foundation Materials Research Science and Engineering Center (MRSEC) on Nanostructured MInterfaces (award #DMR-0079983) and the Beloit College Sanger Program for support of this project.

Instructor Information

www.JCE.DivCHED.org Vol. 82 No. 9 September 2005 Journal of Chemical Educa

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0 10 20 30 40 50 60

Cooling Time /s

PeakR

eflectionWavelength/nm

Figure 3. The wavelength of reflected light (4)cools through its liquid crystal phase. (Coolinnot directly represent temperature; reflection is not expected to be linear with temperature

perforated

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JCE Classroom Activitiesare edited by Erica K. Jacobsen and Julie Cunningham


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Model number Ti45FT

Other Features

Detector size 160 x 120

Detector type Uncooled Microbolometer, Focal Plane Array

Field of View (FOV) 23 horizontal x 17 vertical

Spatial Resolution (IFOV) 2.60 mrad

Minimum Focus Distance 15 cm (approx. 6 in)

Thermal Sensitivity (NETD) 0.08 C at 30 C (80 mK)

Detector data acquisition/

###Image frequency30 Hz or 7.5 Hz

Focus SmartFocus manual

IR Digital Zoom 2x

Spectral Band 8 m to 14m

Transmission Correction (On Imager) No

Reflected Background Temperature

Correction (On Imager)Yes

Measurement modes

Centerpoint Yes

Center box (area, min/max, average) Yes

User defined spots/boxes Yes

Advanced on-board analysis functions YesUser defined field/text annotations Yes

Voice annotation Yes

Automatic hot and cold point detection Yes

Image presentation

Digital display 5" High Resolution LCD

Video output RS170 EIA/NTSC or CCIR/PAL composite video

Palettes 8

Optional lenses

54 mm Telephoto Yes

10.5 mm Wide angle lens Yes

Image and data storage

Storage medium> 1000 images on

compact flash card (1 GB)

On imager file formats IS2

File formats supported in softwareBMP, JPG, GIF, PNG, TIF,

DIB, JPE, JFIF, JPEG, TIFF

Imager features

Fully radiometric Yes

Flash and torch light Yes

Laser pointer Yes

Windows CE based navigation menu Yes

AutoCapture (Programable Image Capture) Yes

180 articulating lens Yes


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00.00.00- 00.00.09

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DYNAMIC-THERMAL BODIES

LORNA PARASHIN

UNIVERSITY OF MANITOBA

PATRICK HARROP

FACULTY OF ARCHITECTURE

M2

2009


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There exists a just noticeable

different between the seen and the unseen, the

heard and the unheard, the touched and the

untouched. Does this just noticeable

differencedisorienate or enliven the senses?

Chris Salterscurrent project explores this edge

between sense reception and cognition. A grid of

panels under a oor vibrates when someone lies

on it. Pressure sensors detect the movement

of the occupant and respond to it. The often

over-looked, at surface of the oor becomes a

sensitive detector

Chris Salter has worked w

Michael Schumacher in Schwelle I

II. The soloist is equiped with body

which respond to his movement an

the dance progresses the dancer c

his improvisational movements and

climate of the room also. The danc

with the micro-climate of the room

climate of the room coexists with th


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works cited

1. Laban, Rudolf. p.2, Choreutics. Jarrold and Sons Limited, Norwich. 1966.

2.Serres, Michael. p. 196, Parasite, Part 3.

3. Laban, Rudolf. p.3 Choreutics. Jarrold and Sons Ltd, Norwich. 1966.

4. Laban, Rudolf. p.24 Mastery of Movement. Macdonald & Evans Ltd, United Kingdom, 1988.

Figure 1. Labanm Rudolf. Choreutics.

Figure 2. Laban, Rudolf. Mastery of Movement.

Figure 3. Laban, Rudolf. Choreutics.

Figure 4. William Forysthe. Improvisational Technologies.

Documents

Lorna Parashin Portfolio 2009