Light Responsive MEMS

8/8/2019 Light Responsive MEMS

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Light Responsive MEMS

Brian Ivancic, Mike Tasevski, Ben Bolyard, Dave Patil


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Problem Description

Reaction times of thermal and chemical expansionOn the slower end of current designsNot easily controlled or sustainable

Large HysteresisRequire large changes in heat or chemical balance to invokechange in shape


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C onceptual IdeasU se of a polymer gel

Easily deformed by external stimuli like lightCan react to these changes with constant temperature andchemical levels

Reduction in reaction timeReach the hysteresis levels fasterEasily measureable and controlled inputDownscaling of gel size results in faster response times


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Polymer gelsPolymer Gel

Defined as a substantially dilute cross-linked systemBehave like solids due to 3-D cross-linking

CrosslinksBond the polymer chains of the gel togetherCan be reoriented with change in intensity of light which inturn provide a large volume transition for the gel.


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C rossl-link Response to Light


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O ptical Switching in Polymer Gels(A.Suzuki, T. Ishii, and Y. Maruyama)


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U se of Polymer gelVolume Change

Swells when in Solution up to 100% of volumeChange in volume can be used to create mechanical work UV or visible light can be used as a stimulus which causescross-links to formCross-links organize the structure of the gel into a shrunkensolid state with certain intensities


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Governing Equation` Light Intensity

` WhereE is the complex amplitude of the electric field` C is the speed of light in a vacuum` e is the vacuum permittivity` n is the refractive index


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Governing Equations` Refractive Index

` Where c is the speed of light in a vacuum

` v is the phase speed of radiation of a specificfrequency in a specificmaterial

` After 280 nm, refractiveindex remains ~1.46


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Governing Equations

Osmotic SwellingP ressure ( )a measure of the force that a given hydro gel, can exert on a pressure sensor

WhereV 1 is the molar volume of water,n1 is the number of moles of water, 1 isthe chemical potential value for water in the hydrogelat ambie nt pressure , and 1,0is the chemical potential value for water in the reference solution that surroundsthe hydrogel.

CapacitanceP arallelP late Capacitor

capacitance is directly proportional to the surface area of the conductor plateand inversely proportional to the separation distance between the plates.

Capacitance of simpleParallelP late is equal to:

Where e is emissivity, A is area, and d is distance


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Design


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Design

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F abrication


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Sensor

Intensity is a function of refractive index

Refractive index is a function of thickness (empirical datn=f(thickness)Time is proportional to thicknessWith two or more different thicknesses, there will be atime difference.

Given certain time differences we can construct acalibration of time difference vs. intensity.


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Applications

Can detect light intensity

Fiber optics will be used to transmit the light to the hydrogelThe fiber optics can be placed in different positions and the

sensors in the array will have different swelling due to differenintensity.The voltage differences can be monitored and used as feedbacfor a direction sensing system.Possibly light communication


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References` Dynamics of Smart Structures, RanjanVepa, 2010` ResponsivePolymer Materials (Designs and Aplications),

Sergiy Minko, 2006` Optical switching in polymer gels, A. Suzuki, T. Ishii, and

Maruyama, 1997

Light Responsive MEMS

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