Скачать презентацию Lectures 17 -18 This lecture covers introductory aspects Скачать презентацию Lectures 17 -18 This lecture covers introductory aspects

b5d94a7bcd6dd4b864ae4e5d57161b04.ppt

  • Количество слайдов: 58

Lectures 17 -18 This lecture covers introductory aspects related to: - Microoptics, Microfluidics Dan Lectures 17 -18 This lecture covers introductory aspects related to: - Microoptics, Microfluidics Dan O. Popa, EE 5349 Microsystems, Summer 2015

Microphotonics (Microoptics) l Photonics: blend of optics and electronics. l Photonic materials/devices/systems. l Brief Microphotonics (Microoptics) l Photonics: blend of optics and electronics. l Photonic materials/devices/systems. l Brief history: • 1870 - John Tyndall’s experiment (water jets as light transmission medium). • 1880 - Alexander Graham Bell’s unguided light carrying speech system. • 1950 – O’Brien & Kapany build first image carrying fibers, used today in fiberscopes. • 1957– 1960 – Gould/Townes/Maiman develop first lasers. • 1966 -1970 Maurer, Keck, and Schultz at Corning invent fiberoptics with low loss, 20 db/km • 1970’s and 1980’s – fiber optic infrastructure built for telephony, improvements in fiber glass manufacturing (losses 0. 2 db/km). • 1990’s and 2000’s – Gigabit ethernet infrastructure based on fiber optics. Dan O. Popa, EE 5349 Microsystems, Summer 2015

Photonic Materials • • Semiconductor Materials • • • Used for light generation, detection, Photonic Materials • • Semiconductor Materials • • • Used for light generation, detection, modulation, fabrication of monolithic devices III-V semiconductors (Ga. As) used in. 65 -1. 55 μm lasers. II-VI, III-N used for visible and UV lasers. Ferroelectric Materials • Used in spatial light modulation, light beam amplification, optical storage. Nonlinear Optical Materials • Crystalline and Polymeric Glass (Silica) • Used for fiber, lenses, collimators. Dan O. Popa, EE 5349 Microsystems, Summer 2015

Photonic Devices • • • Semiconductor diode lasers (LED) • Based on a semiconductor Photonic Devices • • • Semiconductor diode lasers (LED) • Based on a semiconductor diode junction, electron-hole recombination produces photons. Photodetectors • • Inverse of LED’s. PIN, MSM, Avalanche. Solid-State Lasers • • Consists of an active medium with energy levels selectively populated. A pump to produce population inversion. A resonant EM cavity for feedback. Built with glasses doped with rare-earth dopants: Erbium, Yttrium, Thulium, Holmium, Neodymium. Dan O. Popa, EE 5349 Microsystems, Summer 2015

Photonic Devices • Optical modulators • • Used to change the phase, polarization and Photonic Devices • Optical modulators • • Used to change the phase, polarization and amplitude of light. Modulation mechanism: Electro-optic, Acousto-optic, Magneto-optic, Micromechanical, Thermal. Optical Fibers • • • Pioneered by Corning, Inc. Made by removing impurities from glass, and doping it. Advantages of fiber over copper wire: wide bandwidth, low loss, EMI immunity, light weight, small size. Mirrors, Lenses (micro and macro) • Metal, Glass, other dielectric coatings Dan O. Popa, EE 5349 Microsystems, Summer 2015

MOEMS devices • • Micro-opto-electro-mechanical systems (MOEMS). Some of the devices could be fabricated MOEMS devices • • Micro-opto-electro-mechanical systems (MOEMS). Some of the devices could be fabricated using IC technology. Other MOEMS devices require different fabrication and assembly technologies. Can be integrated with electronics on the same chip. Must be scalable to a large number of devices. Must be small and cheap to manufacture. Some require hermetic packaging. Commercial examples of MOEMS: • • • TI Digital Micromirror Array (DLP™) AT&T Microactuated Switch Mirror. Lucent 2 N Micromirror Switch. Dan O. Popa, EE 5349 Microsystems, Summer 2015

Dan O. Popa, EE 5349 Microsystems, Summer 2015 Dan O. Popa, EE 5349 Microsystems, Summer 2015

Challenges in MOEMS • Micro-mirrors are easy to manufacture using IC technology. What about Challenges in MOEMS • Micro-mirrors are easy to manufacture using IC technology. What about integrating micro-lenses, micro-arrays of fiber, etc? • New micro-technology dealing with glass must be developed, including micro-grasping, micro-positioning and bonding. • Cost effective/ large quantity automated assembly systems for MOEMS are not currently available. • • • The management of large number of fibers in MOEMS devices. Scalable designs of MOEMS. Fluxless attachment/hermetic packaging for long term reliability. Dan O. Popa, EE 5349 Microsystems, Summer 2015

Introduction to fiber-optics • • • Fiber components: core, cladding, buffer, jacket. Materials used: Introduction to fiber-optics • • • Fiber components: core, cladding, buffer, jacket. Materials used: glass, plastic (PFO). Multimode/singlemode operation – variable diameter: • • 62. 5 µm core, LED, used in LAN 9 µm core, laser, used in CATV, telephony. Wavelength: • • • IR 850 nm-1300 nm(Multimode) IR 1300 nm-1550 nm(Singlemode) Visible & IR 650 nm-850 nm Wave source: LED, laser (VCSEL, vertical cavity surface emitting laser) Dan O. Popa, EE 5349 Microsystems, Summer 2015

Geometry of fibers • • • Light is guided inside the core by reflection Geometry of fibers • • • Light is guided inside the core by reflection off cladding. The coating protects the fiber from humidity and damage. Cladding and core are ultra-pure glass with slightly different refraction indexes. • Standard core/cladding diameter is 125 µm, overall fiber diameter is 250 µm. Dan O. Popa, EE 5349 Microsystems, Summer 2015

Specialized jargon • • Splices, connectors. • • • Power Meters. • • ODTRs Specialized jargon • • Splices, connectors. • • • Power Meters. • • ODTRs (optical time domain reflectometer): measures backscattered light from a source. Wavelength Division Multiplexers/Demultiplexers (WDM). Fiber optics amplifiers/repeaters, switches. Scattering: direction, frequency, or polarization changes. Dispersion: Any phenomenon in which the velocity of propagation is wavelength dependent Loss in db, depends on wavelength: • • • Connector loss ~ 0. 5 db Splice loss ~ 0. 2 db Multimode 3 db/km (850 nm), 1 db/km(1300 nm) Singlemode 0. 4 db/km (1300 nm), 0. 3 db/km(1150 nm) Bending losses Optical power: dbm. Dan O. Popa, EE 5349 Microsystems, Summer 2015

Propagation mode • • Multi-mode vs. single-mode. Refractive index profile can be step (uniform Propagation mode • • Multi-mode vs. single-mode. Refractive index profile can be step (uniform in core) or graded. • Propagation modes are solutions to Maxwell’s equations. Dan O. Popa, EE 5349 Microsystems, Summer 2015

Acceptance cone and NA Snell’s law: θ 1 θ 2 Dan O. Popa, EE Acceptance cone and NA Snell’s law: θ 1 θ 2 Dan O. Popa, EE 5349 Microsystems, Summer 2015

Fiber Characteristics • Modal dispersion (for multi-mode fibers), modes traveling at different speeds. • Fiber Characteristics • Modal dispersion (for multi-mode fibers), modes traveling at different speeds. • • Material dispersion, wavelength dependent velocity. Polarization mode dispersion (for single-mode fibers), two polarization states traveling at different speeds. • Waveguide dispersion, light traveling in core and cladding at slightly different speeds. • • Bandwidth & Attenuation, absorption. Fiber strength, bend radius, nuclear hardness. Dan O. Popa, EE 5349 Microsystems, Summer 2015

Wave propagation equations through fiber Maxwell’s equations: E – electric field, H – magnetic Wave propagation equations through fiber Maxwell’s equations: E – electric field, H – magnetic field, D, B – flux densities, P, M – polarization and magnetization. Dan O. Popa, EE 5349 Microsystems, Summer 2015

Wave propagation equations through fiber From Maxwell’s equations I and II: At the same Wave propagation equations through fiber From Maxwell’s equations I and II: At the same time: Therefore we obtain a vector “wave equation”: Dan O. Popa, EE 5349 Microsystems, Summer 2015

Wave propagation equations through fiber Wave equation solved via separation of variables Define the Wave propagation equations through fiber Wave equation solved via separation of variables Define the free-space wave number as In cylindrical coordinates Dan O. Popa, EE 5349 Microsystems, Summer 2015

Wave propagation equations through fiber Final wave equation: In grade mode fiber, n is Wave propagation equations through fiber Final wave equation: In grade mode fiber, n is a function of r, and can take the optimal form: For step index fiber, n is uniform in the core, and the wave equation can be solved via Bessel functions, such that is a zero of It can be shown that if the diameter of the fiber decreases below a cutoff value, only one Bessel function is possible (i. e. , one mode). Dan O. Popa, EE 5349 Microsystems, Summer 2015

Propagation away from fiber tip Dan O. Popa, EE 5349 Microsystems, Summer 2015 Propagation away from fiber tip Dan O. Popa, EE 5349 Microsystems, Summer 2015

Fiber handling • Fiber must be attached to opto-electronic devices, therefore it must be: Fiber handling • Fiber must be attached to opto-electronic devices, therefore it must be: • • • Picked up, placed and fixtured in place. Bonded using adhesives or other techniques. Aligned to the rest of the optical system components. • Current state of the art for picking/handling/aligning fiber: microgrippers for “one fiber at a time” handling. Many vendors of such hardware: Newport, Thor Labs, etc. • Current state of the art for fixturing fibers: V-grooves, Ferrules. • Current state of the art for bonding fiber: adhesives cured at room temperature, through heat, or exposure to ultraviolet light, solder reflow for high precision connectors. Dan O. Popa, EE 5349 Microsystems, Summer 2015

Fiber Microgrippers PZT actuation • Piezojena: 385 m opening – EDM machined 90 V-groove Fiber Microgrippers PZT actuation • Piezojena: 385 m opening – EDM machined 90 V-groove • Klocke Nanotechnik: 500 m opening – EDM machined tips Dan O. Popa, EE 5349 Microsystems, Summer 2015

Fiber handling • Fiber fixtures: V-grooves and Ferrules for “pigtailing” Dan O. Popa, EE Fiber handling • Fiber fixtures: V-grooves and Ferrules for “pigtailing” Dan O. Popa, EE 5349 Microsystems, Summer 2015

Clamping Method for Fiber Array Manufacturing • Finger-groovemechanism Dan O. Popa, EE 5349 Microsystems, Clamping Method for Fiber Array Manufacturing • Finger-groovemechanism Dan O. Popa, EE 5349 Microsystems, Summer 2015

Fiber Splice Losses • Loss factors mostly due to alignment Dan O. Popa, EE Fiber Splice Losses • Loss factors mostly due to alignment Dan O. Popa, EE 5349 Microsystems, Summer 2015

Fiber Alignment • Light transmission loss is parabolic with d and q Dan O. Fiber Alignment • Light transmission loss is parabolic with d and q Dan O. Popa, EE 5349 Microsystems, Summer 2015

Fiber Alignment Algorithms Model-based alignment method Gradient-based search Conical scanning search MBA decreased search Fiber Alignment Algorithms Model-based alignment method Gradient-based search Conical scanning search MBA decreased search time by a factor of 10 [Sin & Popa 2003] Dan O. Popa, EE 5349 Microsystems, Summer 2015

Fiber Connectors Kevlar Plastic Jacket Fiber Cladding Fiber stripping Fiber connector Mechanical Pinchers Metal Fiber Connectors Kevlar Plastic Jacket Fiber Cladding Fiber stripping Fiber connector Mechanical Pinchers Metal Collar Fiber insertion into ferrule Connector hole with polished fiber Dan O. Popa, EE 5349 Microsystems, Summer 2015

Optical Fiber Insertion Into Ceramic Ferrule Measured Computed Laser intensity around the hole of Optical Fiber Insertion Into Ceramic Ferrule Measured Computed Laser intensity around the hole of connector Dan O. Popa, EE 5349 Microsystems, Summer 2015 Laser intensity during insertion

Alignment of fiber arrays using ASD • • • Automated alignment of optical fiber Alignment of fiber arrays using ASD • • • Automated alignment of optical fiber array using pneumatic active surface device 2 x 1 fiber array with wet etched Si grooves [J. Sin, Ph. D Thesis, 2002] Nx 1 and Nx. N fiber arrays used as I/O to optical switches presented before Dan O. Popa, EE 5349 Microsystems, Summer 2015

Substrate waveguides • Mach-Zehnder interferometer for pressure sensing 14 µV/mbar, 0. 3 mm x Substrate waveguides • Mach-Zehnder interferometer for pressure sensing 14 µV/mbar, 0. 3 mm x 5 mm prototype Dan O. Popa, EE 5349 Microsystems, Summer 2015

Micro. Optical Benches Dan O. Popa, EE 5349 Microsystems, Summer 2015 Micro. Optical Benches Dan O. Popa, EE 5349 Microsystems, Summer 2015

Case study: MEMS Gas Analyzer – ARRI - 2004 -2008 FTIR: Fourier Transform Infra. Case study: MEMS Gas Analyzer – ARRI - 2004 -2008 FTIR: Fourier Transform Infra. Red Spectrometer (for light wavelength detection) GC: Gas Chromatograph (for gas molecule separation) Micropump FTIR Mirror Beam splitter IR GC Gas inlet Gas outlet Mirror Lens LD Detector IR Detector Light pipe Battery Dan O. Popa, EE 5349 Microsystems, Summer 2015 Electronics DSP

Case study: MEMS Gas Analyzer Technology needed to construct this device: - Scaling, modeling, Case study: MEMS Gas Analyzer Technology needed to construct this device: - Scaling, modeling, analysis - Si microactuators: design and fabrication - Position sensing (Capacitive) - Microassembly of Si and Glass components - Fiber/optical alignment and attachment - Embedded IC detectors on MEMS die - Microfluidic channels for gas handling - IC electronics for signal conditioning, capture, transform - Packaging of Optical MEMS Bench - Packaging of Electronics - Wafer-scale packaging of fluidics Dan O. Popa, EE 5349 Microsystems, Summer 2015

FTIR: Design Specifications • Sensitivity: IR Absorption (Beer-Lambert Law) is relationship with absorbance and FTIR: Design Specifications • Sensitivity: IR Absorption (Beer-Lambert Law) is relationship with absorbance and concentration of sample A=log 10(I 0/I)= Lc : absorption coeff. L: light path length C: concentration of absorbing species Laser (635 nm) • Selectivity: spectral resolution or Beam splitter Lens Mirror Example: x=1 mm, opd=2 x=2 mm, resulting in 12. 5 nm resolution for 5. Detector Dan O. Popa, EE 5349 Microsystems, Summer 2015

Mirror Scanning for FTIR Thermal actuator lever mechanism, electrothermal 50 µm stroke, vertical assembled Mirror Scanning for FTIR Thermal actuator lever mechanism, electrothermal 50 µm stroke, vertical assembled mirror 450µm height Dan O. Popa, EE 5349 Microsystems, Summer 2015

Microspectrometer with embedded optoelectronics Laser diode chip Detector chip Actuator ARRI – 2004 -2008 Microspectrometer with embedded optoelectronics Laser diode chip Detector chip Actuator ARRI – 2004 -2008 Fixed mirror Dan O. Popa, EE 5349 Microsystems, Summer 2015 Scanning mirror

Gas Chromatography Dan O. Popa, EE 5349 Microsystems, Summer 2015 Gas Chromatography Dan O. Popa, EE 5349 Microsystems, Summer 2015

Microfluidics • Direct/rout the flow of fluids for analysis (sensing) or actuation. • Passive Microfluidics • Direct/rout the flow of fluids for analysis (sensing) or actuation. • Passive components: channels, reservoirs, I/O ports • Active components: valves, pumps • Integrated sensors: sensors (photonic, biological, etc), heaters, actuators. • Supporting electronics, power. • Materials: Si, Si. C, metals, ceramics (harsh environments), glass (bio), polymers (bio, disposable). Dan O. Popa, EE 5349 Microsystems, Summer 2015

Applications of Microfluidics • µTAS: point of care • Chemical analysis • Microelectronic cooling Applications of Microfluidics • µTAS: point of care • Chemical analysis • Microelectronic cooling circuits • Implantable devices chronic pain relief, arterial infusion for cancer and insulin delivery Dan O. Popa, EE 5349 Microsystems, Summer 2015

Types of Pumps Displacement Dynamic Reciprocating Centrifugal Diaphragm ·Piezoelectric ·Lateral, axial ·Thermopneumatic, Pneumatic Electrohydrodynamic Types of Pumps Displacement Dynamic Reciprocating Centrifugal Diaphragm ·Piezoelectric ·Lateral, axial ·Thermopneumatic, Pneumatic Electrohydrodynamic • Injection ·Induction ·Conduction Piston Electro-osmotic ·Porous, Micromachined Rotary Aperiodic Magnetohydrodynamic ·DC, AC Acoustic streaming/Ultrasonic “Introduction: classification and selection of pumps, ” Krutzch W C and Cooper P, Pump Handbook ed I J Karassik et al (New York: Mc. Graw-Hill), 2001. Dan O. Popa, EE 5349 Microsystems, Summer 2015 Miscellaneous

Micropumps-Applications • Drug delivery – Pain management. Synchro. Med Iso. Med – Diabetes-Minimed (Medtronics) Micropumps-Applications • Drug delivery – Pain management. Synchro. Med Iso. Med – Diabetes-Minimed (Medtronics) • Research – Implantable. Nanopump (Debiotech), EKpump (Exigent) nl to µl per minute Dan O. Popa, EE 5349 Microsystems, Summer 2015

Valveless Diaphragm Pumps Center for Wireless Integrated Microsystem (WIMS). University of Michigan** The valveless Valveless Diaphragm Pumps Center for Wireless Integrated Microsystem (WIMS). University of Michigan** The valveless diaphragm pumps depend on the nozzle geometry to produce a net flow, while the electrohydrodynamic (EHD) pumps create ions in the fluid and move them along in a "stepper motor" fashion. (Cooling Technologies Research Center at Purdue University, West Lafayette, Ind. ) Dan O. Popa, EE 5349 Microsystems, Summer 2015

Electrostatic Micropump • 7 mm x 2 mm • Membrane area 16 mm 2 Electrostatic Micropump • 7 mm x 2 mm • Membrane area 16 mm 2 • Thickness of 50 • 6. 3 between membrane and electrode • With 170 V and 25 HZ, rate is 70 l/min Dan O. Popa, EE 5349 Microsystems, Summer 2015

Electrostatic Microvalve • Membrane bends up due to inner stresses • Coated with chrome Electrostatic Microvalve • Membrane bends up due to inner stresses • Coated with chrome layer (electrode) • Valve openings 10 x 10 2 • 100 V operation Dan O. Popa, EE 5349 Microsystems, Summer 2015

Foil-like Actuator • Workspace of about 40 mm • Fe. Ni foil 12 mm Foil-like Actuator • Workspace of about 40 mm • Fe. Ni foil 12 mm wide and 5 thick • 4 m/s at 150 V Dan O. Popa, EE 5349 Microsystems, Summer 2015

In-Plane Micropump (ARRI – 2004 -2007) • Integrate actuators, valves, pump diaphragm in one In-Plane Micropump (ARRI – 2004 -2007) • Integrate actuators, valves, pump diaphragm in one silicon die. Actuator Lever mechanism Diaphragm Valve Three layer die packaging Dan O. Popa, EE 5349 Microsystems, Summer 2015

SOI-DRIE Fabrication and Packaging • • SOI wafer Doping Deep RIE device layer Deep SOI-DRIE Fabrication and Packaging • • SOI wafer Doping Deep RIE device layer Deep RIE handle layer Release Metal deposition Wafer bonding Deposited metal Device layer Handle layer Dan O. Popa, EE 5349 Microsystems, Summer 2015 Buried silicon oxide

Pump Diaphragm • Actuation with 10 V sinusoidal, 3 Hz input. Dan O. Popa, Pump Diaphragm • Actuation with 10 V sinusoidal, 3 Hz input. Dan O. Popa, EE 5349 Microsystems, Summer 2015 • The diaphragm itself is very flexible to allow high compression ratio.

In-Plane Micropump (ARRI – 2004 -2007) Diffuser-nozzle design Raw Actuator Force ~ 0. 98 In-Plane Micropump (ARRI – 2004 -2007) Diffuser-nozzle design Raw Actuator Force ~ 0. 98 m. N Bandwidth ~ 45 Hz Flow rate: 75µl/min, against 8 mm Hg (vein) Using lumped model Dan O. Popa, EE 5349 Microsystems, Summer 2015

Microchannel materials: PDMS Molding Photoresist (SU-8, negative) Photolithography 100 m Silicon wafer SU-8 mold Microchannel materials: PDMS Molding Photoresist (SU-8, negative) Photolithography 100 m Silicon wafer SU-8 mold master Pour PDMS 100 m Remove master Bond with glass Dan O. Popa, EE 5349 Microsystems, Summer 2015 PDMS channel structures can be bonded using plasma oxidation.

Microchannel materials: Glass • Channel fabrication on photosensitive etchable glass wafer. Holes for tube Microchannel materials: Glass • Channel fabrication on photosensitive etchable glass wafer. Holes for tube interconnection Channel Reservoir Top surface 10 m 100 m wide channels Dan O. Popa, EE 5349 Microsystems, Summer 2015 Vertical (etched surface)

Microchannel materials: LTCC (Ceramics) Via forming (fluidic channel), punching, or laser drilling Via filling Microchannel materials: LTCC (Ceramics) Via forming (fluidic channel), punching, or laser drilling Via filling Screen printing of conductive material Collating and laminating Co-firing Dan O. Popa, EE 5349 Microsystems, Summer 2015

Microchannel materials: Silicon Developed etchable glass wafer Spin coating BCB Etching in HF RIE Microchannel materials: Silicon Developed etchable glass wafer Spin coating BCB Etching in HF RIE BCB layer Bonding with other wafers Dan O. Popa, EE 5349 Microsystems, Summer 2015

Fluidic Interconnects [1] Gray, B. L. , Collins S. D. and Smith R. , Fluidic Interconnects [1] Gray, B. L. , Collins S. D. and Smith R. , L. , “Interlocking mechanical and fluidic interconnections for microfluidic circuit boards, ” Sensors and Actuators A 112 (2004) 18– 24. [2] Lee E. , Howard D. , Liang E. , Collins S. D. and Smith R. L. , “Removable tubing interconnects for glass-based micro-fluidic systems made using ECDM, ” J. Micromech. Microeng. 14 (2004) 535– 541. [3] Aniruddha Puntambekar and Chong H Ahn, “Self-aligning microfluidic interconnects for glass- and plastic-based Microfluidic systems, ” J. Micromech. Microeng. 12 (2002) 35– 40. Dan O. Popa, EE 5349 Microsystems, Summer 2015

Fluidic Interconnects [4] Meng E. , Wu S. and Tai Y. C. , “Silicon Fluidic Interconnects [4] Meng E. , Wu S. and Tai Y. C. , “Silicon couplers for microfluidic applications, ” Fresenius J Anal Chem (2001) 371 : 270– 275. [5] Tsai H. and Lin L. , “Micro-to-macro fluidic interconnectors with an integrated polymer sealant, ” J. Micromech. Microeng. 11 (2001) 577– 581. [6] Chen H. , Acharya D. , Gajraj A. and Meiners J. C>, ”Robust Interconnects and Packaging for Microfluidic Elastomeric Chips, ” Anal. Chem. 2003, 75, 5287 -5291. [7] Li S. and Chen S. , “Polydimethylsioxane Fluidic Interconnects for Microfluidic Systems, ” IEEE TRANSACTIONS ON ADVANCED PACKAGING, VOL. 26, NO. 3, AUGUST 2003. [8] Andrew M Christensen, David A Chang-Yen and Bruce K Gale. , “Characterization of interconnects used in PDMS microfluidic systems”, J. Micromech. Microeng. 15 (2005) 928– 934 Dan O. Popa, EE 5349 Microsystems, Summer 2015

Modular Polymer Microfluidics • Pursued by several research groups, and companies - Kionics Inc. Modular Polymer Microfluidics • Pursued by several research groups, and companies - Kionics Inc. , Epigem, Fluidigm Dan O. Popa, EE 5349 Microsystems, Summer 2015

Bonded Platform with out embedded valve (ARRI – 2005 -2006) PDMS Microchannels, Sub mm Bonded Platform with out embedded valve (ARRI – 2005 -2006) PDMS Microchannels, Sub mm interconnects 50 -100 psi pressure Dan O. Popa, EE 5349 Microsystems, Summer 2015

Readings for Week 16 • Fatikow Text, Chapters 6, 8 • Madou Text, Chapters Readings for Week 16 • Fatikow Text, Chapters 6, 8 • Madou Text, Chapters 8, 9 Dan O. Popa, EE 5349 Microsystems, Summer 2015