Lecture 15 and 16: MicroStereoLithography (MSL) ME 645: MEMS: ME 645: MEMS: Design Fabrication Design Fabrication Design, Fabrication Design, Fabrication and Characterization and Characterization P.S. Gandhi P.S. Gandhi Mechanical Engineering Mechanical Engineering IIT Bombay IIT Bombay Acknowledgments: Suhas Deshmukh (PhD 08) Rahul Ramtekkar (M Tech 08) and other M Tech students PRASANNA S GANDHI gandhi@me.iitb.ac.in PRASANNA S GANDHI gandhi@me.iitb.ac.in Motivation Motivation Need for Microstereolithography Need for Microstereolithography Need for Microstereolithography Need for Microstereolithography MEMS MEMS – – Worldwide Research attention Worldwide Research attention � Requirement of current actuating and sensing Requirement of current actuating and sensing mechanisms to be of complex 3D shapes. mechanisms to be of complex 3D shapes. � Incorporation of a wide range of materials Incorporation of a wide range of materials Limitations of Conventional Limitations of Conventional processes : processes : � manufacture high aspect ratio and complex manufacture high aspect ratio and complex 3D microstructures. 3D microstructures. PRASANNA S GANDHI gandhi@me.iitb.ac.in PRASANNA S GANDHI gandhi@me.iitb.ac.in 1
What is What is Microstereolithography Microstereolithography? ? Laser beam Part to manufacture � Novel Novel microfabrication microfabrication process for fabricating high process for fabricating high aspect ratio and complex 3D aspect ratio and complex 3D 3 rd Layer microstructures. microstructures. 2 nd Layer � Evolved from the rapid Evolved from the rapid 1 st Layer prototyping industry. prototyping industry. � UV laser beam scanned on a UV laser beam scanned on a photopolymerizable resin. photopolymerizable resin. Mirror UV Light Light Elevator El � Curing of the resin layer by Curing of the resin layer by layer. layer. Vat of UV � Stacking of all the layers. Stacking of all the layers. curable solution � In case of ceramic materials In case of ceramic materials process of laser sintering is process of laser sintering is used used PRASANNA S GANDHI gandhi@me.iitb.ac.in PRASANNA S GANDHI gandhi@me.iitb.ac.in SLA to MSL SLA to MSL Item Parameters Stereolithography Micro- stereolithography Optical Spot Size Approx. 100 μ m Few μ ms System Intensity Non-uniform Uniformity is profile during scanning necessary for high resolution Scanning Resolution Less than 100 μ ms Less than 1 μ m is System is sufficient needed Photopolymer Viscosity High Low Support Needed Is not needed Generation PRASANNA S GANDHI gandhi@me.iitb.ac.in PRASANNA S GANDHI gandhi@me.iitb.ac.in 2
Microstereolithography Microstereolithography Process Types � Dynamic mask method (Integral MSL): Dynamic mask method (Integral MSL): � – Expose the layer to be built at a time Expose the layer to be built at a time – Change the mask dynamically Change the mask dynamically – Expose the next layer Expose the next layer � Scanning method: Scanning method: Scanning method: Scanning method: � – Scan one layer by focused laser beam and Scan one layer by focused laser beam and then the next layer then the next layer PRASANNA S GANDHI gandhi@me.iitb.ac.in PRASANNA S GANDHI gandhi@me.iitb.ac.in Microstereolithography Microstereolithography Dynamic mask process Integral MSL systems Dynamically changing Dynamically changing Dynamically changing Dynamically changing mask according to the mask according to the section to be exposed section to be exposed Computer Dynamic Mask Elevetor z Laser curable photopolymer Generates image of a layer and complete layer is build in PRASANNA S GANDHI gandhi@me.iitb.ac.in PRASANNA S GANDHI gandhi@me.iitb.ac.in single layer 3
Scanning Method Scanning Method � Classical Classical msl msl – Focusing by a dynamic lens Focusing by a dynamic lens Micro C.A.D. – Use of galvanometric mirrors Use of galvanometric mirrors computer � Theoretical best point of Theoretical best point of � focus not intersecting the focus not intersecting the Galvanometric X-Y mirrors Acousto optical shutter resin surface. resin surface. U.V. Z - stag Laser � Free surface technique Free surface technique Free surface technique Free surface technique Dynamic y ge focusing lens � All optical parts fixed All optical parts fixed � X- -Y Y- -Z motorized translation Z motorized translation Photoreactor stage stage � Thickness and uniformity Thickness and uniformity control of deposited liquid layer control of deposited liquid layer PRASANNA S GANDHI gandhi@me.iitb.ac.in PRASANNA S GANDHI gandhi@me.iitb.ac.in difficult difficult Scanning Method Scanning Method Vector Scan � Schematic diagram Schematic diagram � Mirror Laser Elevator z Laser curable photopolymer PRASANNA S GANDHI gandhi@me.iitb.ac.in PRASANNA S GANDHI gandhi@me.iitb.ac.in 4
Various MSL Systems Various MSL Systems Scanning method or vector by vector MSL. Scanning method or vector by vector MSL. � Various ways of scanning Various ways of scanning Various ways of scanning Various ways of scanning Integral Integral microstereolithography microstereolithography . � 1. Liquid crystal display as pattern generator 1. Liquid crystal display as pattern generator 2. Digital micromirror 2. Digital micromirror device as pattern device as pattern generator generator Creating an object inside reactive Creating an object inside reactive medium medium � 1 Two photon process 1.Two photon process 1.Two photon process 1 Two photon process 2. Single 2. Single photon photon process process Method of layer preparation Method of layer preparation � 1. Constrained surface technique. 1. Constrained surface technique. 2. Free surface technique 2. Free surface technique PRASANNA S GANDHI gandhi@me.iitb.ac.in PRASANNA S GANDHI gandhi@me.iitb.ac.in 3. Super IH (Integrated Harden) process technique 3. Super IH (Integrated Harden) process technique Constrained and Free Constrained and Free Surface MSL Surface MSL UV Source UV Source Optical Optical Constrained Free Shutter Shutter Surface Surface Surface Surface Z-Stage Z-Stage Fabricated Fabricated Structure Structure Micro- Micro- Controller Controller Resin Tank Resin Tank XY Stage XY Stage C Constrained Surface MSL Systems Constrained Surface MSL Systems C t t i i d S d S f f MSL S MSL S t t Free Surface MSL Systems F Free Surface MSL Systems F S S f f MSL S MSL S t t Features: Features:- - Features: Features:- - Layer thickness is controlled by Layer thickness is controlled by � Recoating blade Recoating blade Transparent Glass Window is used Transparent Glass Window is used � Controls layer thickness Controls layer thickness XY Scanning by Resin Tank Motion XY Scanning by Resin Tank Motion � Laser spot is at focus on the resin Laser spot is at focus on the resin � No Destruction of fabricated part No Destruction of fabricated part � XY Scanning by Resin Tank Motion XY Scanning by Resin Tank Motion � PRASANNA S GANDHI gandhi@me.iitb.ac.in PRASANNA S GANDHI gandhi@me.iitb.ac.in Waviness of fabricated part due to tank Waviness of fabricated part due to tank � Destruction of fabricated part Destruction of fabricated part motion motion � 5
Scanning Method Scanning Method Variations 1. Fixed optics, move liquid tank for xy 1. Fixed optics, move liquid tank for xy scanning scanning 2. Various ways for scanning 2. Various ways for scanning - Rotating galvano Rotating galvano- -scanning mirrors scanning mirrors - Linearly moving mirrors (novel way) Linea l Linea l Linearly moving mirrors (novel way) mo ing mi o s (no el mo ing mi o s (no el a ) a ) - Raster scan vs vector scan Raster scan vs vector scan PRASANNA S GANDHI gandhi@me.iitb.ac.in PRASANNA S GANDHI gandhi@me.iitb.ac.in Various Scanning Various Scanning Methods Depicted Methods Depicted L L L M M M M M L L M Post-objective Pre-objective Photo-reactor tank Off-axis Lens Proposed by us recently * p y y • Suhas Deshmukh, S. Dubey, P.S. Gandhi, “Optical Analysis of Scanning Microstereolithography systems” , Proceedings of the SPIE Symposium on MOEMS-MEMS Micro & Nanofabrication, San Jose, CA USA, January 2006 •Suhas P. Deshmukh, P.S. Gandhi, “Optomechanical Scanning Systems for Microstereolithography (MSL): Analysis an Experimental Verification” , Journal of Material Processing Technology PRASANNA S GANDHI gandhi@me.iitb.ac.in PRASANNA S GANDHI gandhi@me.iitb.ac.in 6
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