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1/2/2017 Prof. Steven S. Saliterman Introductory Medical Device Prototyping Department of Biomedical Engineering, University of Minnesota www.tc.umn.edu/~drsteve A sensor converts one form of energy to another, and in so doing detects and conveys information about some physical, chemical or biological phenomena. More specifically, a sensor is a transducer that converts the measurand (a quantity or a parameter) into a signal that carries information. For our purposes, we are generally trying to convert the measurand into an electrical signal that can be input into a microcontroller. Prof. Steven S. Saliterman Something in our environment: Biomedical: ◦ Ambient temperature, barometric pressure, humidity, gas, light, dust, air quality, water quality, soil moisture, and radiation. ◦ Blood pressure, pulse, body temperature, height, weight, respiratory rate, laboratory (blood, urine, cerebral spinal fluid); respiratory and blood gasses, flow (blood, urine and air), intraocular, intracranial and tympanic membrane pressures; electrocardiogram, electrical activity of muscles and nerves, and internal organ imaging (x-ray, ultrasound, camera, NMR). Prof. Steven S. Saliterman 1 1/2/2017 Other physical measurements: ◦ Stress, stain, strength, pressure, distances, magnetic fields, sound, light, water levels, motion (acceleration), orientation (gyro), proximity and location (GPS). Images User interactions: ◦ Tactile, button presses, flexion, knob turning; hand and other body part motion, and eye movement tracking. Prof. Steven S. Saliterman Sensors may be classified based on the following: ◦ Measurand - temperature, pressure, flow etc. ◦ Transduction (physical and chemical effects) - SAW, ion selective FETs, optodes (chemical transducer) etc. ◦ Materials - resistive, piezoelectric, magnetic, permeable membranes, etc. ◦ Technology – MEMS, bioMEMS, plasmon resonance, CMOS imaging, charge coupled devices etc. ◦ Energy requirement - active or passive. ◦ Applications - industrial, automative, aviation, consumer electronics, biomedical etc. Prof. Steven S. Saliterman Continuous operation without effecting the measurand. Appropriate sensitivity and selectivity. Fast and predictable response. Reversible behavior. High signal to noise ratio. Compact Immunity to environment. Easy to calibrate. Prof. Steven S. Saliterman 2 1/2/2017 Prof. Steven S. Saliterman If the bridge resistors have the same value, equal to the strain gauge's resistance at rest, then the voltage is zero. The voltage can be amplified to get a higher sensitivity for the complete circuit. This can be done with a high gain instrumentation amplifier The instrumentation amplifier inputs replace the volt meter in the top circuit. Karki, J. Texas Instruments: Signal Conditioning Wheatstone Resistive Bridge Sensors. Application Report, SLOA034, September 1999. Direct transduction from mechanical to electrical domains and vice versa. May be used as sensors or actuators. The reversible and linear piezoelectric effect manifests as the production of a charge (voltage) upon application of stress (direct effect) and/or as the production of strain (stress) upon application of an electric field (converse effect). Three modes of operation depending on how the piezoelectric material is cut: transverse, longitudinal and shear. Amplifiers are needed to detect the small voltage. Prof. Steven S. Saliterman Tadigadapa, S., and K. Mateti. 2009. Piezoelectric MEMS sensors: state-of-the-art and perspectives. Measurement Science & Technology 20, no. 9:092001. Converse Piezoelectric Effect - Application of an electrical field creates mechanical deformation in the crystal. Polling - Random domains are aligned in a strong electric field at an elevated temperature. Direct Piezoelectric Effect - When a mechanical stress (compressive or tensile) is applied a voltage is generated across the material. Prof. Steven S. Saliterman Adopted from bme240.eng.uci.edu 3 1/2/2017 The piezoelectric effect is a linear phenomenon where deformation is proportional to an electric field: S = dE and D = dT W h ere S is th e m ech an ical strain , d is th e piezo electric co efficient, E is th e electric field , D is the d isp lacm ent (o r ch arg e d en sity ) lin early, an d T is th e stress. These equations are known as the converse piezoelectric effect and the direct piezoelectric effect respectively. Prof. Steven S. Saliterman Prof. Steven S. Saliterman Crystals Ceramics ◦ ◦ ◦ ◦ ◦ Tadigadapa, S., and K. Mateti. 2009. Piezoelectric MEMS sensors: state-of-the-art and perspectives. Measurement Science & Technology 20, no. 9:092001. Quart SiO2 Berlinite AlPO4 Gallium Orthophosphate GaPO4 Tourmaline (complex chemical structure) ◦ Barium titanate BaTiO3 ◦ Lead zirconate titanate PZT, Pb [ZrxTi1-x] O3 ; x = 0,52 Other Materials ◦ Zinc oxide ZnO ◦ Aluminum nitride AlN ◦ Polyvinylidene fluoride PVDF Prof. Steven S. Saliterman Adopted from Piezomaterials.com 4 1/2/2017 V O ut RF QT C T C P R1 V O ut Prof. Steven S. Saliterman Tadigadapa, S., and K. Mateti. 2009. Piezoelectric MEMS sensors: state-of-the-art and perspectives. Measurement Science & Technology 20, no. 9:092001. Piezoelectric sensors maybe configured as direct mechanical transducers or as resonators. The observed resonance frequency and amplitude are determined by the physical dimensions, material and mechanical and interfacial inputs to the device. Prof. Steven S. Saliterman QT CF Tadigadapa, S., and K. Mateti. 2009. Piezoelectric MEMS sensors: state-of-the-art and perspectives. Measurement Science & Technology 20, no. 9:092001. Generation of surface acoustic waves (SAW) in quartz by interdigitated transducers: Prof. Steven S. Saliterman Gardner, JW, VK Varadan and OO Awadelkarim, Microsensors, MEMS and Smart Devices. John Wiley & Sons, Ltd. W. Sussex (2001). 5 1/2/2017 Typically with a sensing film such polyimide deposited on the surface in the area between the interdigitated transducers: Prof. Steven S. Saliterman Prof. Steven S. Saliterman Gardner, JW, VK Varadan and OO Awadelkarim, Microsensors, MEMS and Smart Devices. John Wiley & Sons, Ltd. W. Sussex (2001). Tadigadapa, S., and K. Mateti. 2009. Piezoelectric MEMS sensors: state-of-the-art and perspectives. Measurement Science & Technology 20, no. 9:092001. Biomedical Micro Electro-Mechanical Systems. (The science of very small biomedical devices.) Subset of MEMS/MST (Microsystem Technology). At least one dimension from ~100 nm to 200 µm New materials, understanding of the microenvironment, and biocompatibility. Harnessing any phenomenon that accomplishes work at the microscale. Work may be at the microscale alone, or through some multiplication process at the macroscale. Prof. Steven S. Saliterman 6 1/2/2017 Reactive ion etching – a subtractive process. Low pressure chemical vapor deposition (LPCVD)- an additive process. Prof. Steven S. Saliterman Laboratory Diagnostic Tools: ◦ Microsensors & Microactuators, ◦ Lab-on-a-Chip Devices (LOC), ◦ Micro Total Analysis Systems (µTAS), ◦ DNA and Protein Microarrays. Individualized Treatments Tissue Scaffolding Devices Medication Delivery Devices Minimally Invasive Procedures Platform for Nanomedicine Technologies Homeland Security Prof. Steven S. Saliterman Image Courtesy of Sandia National Laboratories Sub-µm IDEs Surface Acoustic Wave Polymer FETs (proteins, DNA) (proteins) (pH, glucose) © KdK20 02 Magnetic-bead Biosensor Transmission Plasmon Biosensor (proteins, DNA) (proteins, DNA) Prof. Steven S. Saliterman GaAs MESFETs (neurons, proteins) Image Courtesy of Campitelli A, IMEC 7 1/2/2017 Piezoresistive pressure sensor with reference pressure cavity inside chip. Prof. Steven S. Saliterman Esashi, Masayoshi. 2012. Revolution of Sensors in Micro-Electromechanical Systems. Japanese Journal of Applied Physics 51, no. 8:080001. Integrated capacitive pressure sensor fabricated by wafer level packaging. Prof. Steven S. Saliterman Esashi, Masayoshi. 2012. Revolution of Sensors in Micro-Electromechanical Systems. Japanese Journal of Applied Physics 51, no. 8:080001. Principle and photograph of SAW passive wireless pressure sensor and example of measurement (change in time converted into phase). Prof. Steven S. Saliterman Esashi, Masayoshi. 2012. Revolution of Sensors in Micro-Electromechanical Systems. Japanese Journal of Applied Physics 51, no. 8:080001. 8 1/2/2017 Common two-wire tactile sensor network that sequentially selects sensors. Prof. Steven S. Saliterman Esashi, Masayoshi. 2012. Revolution of Sensors in Micro-Electromechanical Systems. Japanese Journal of Applied Physics 51, no. 8:080001. Schematic of event-driven (interrupt) tactile sensor network, example of operation, and photographs of prototype IC. Prof. Steven S. Saliterman Esashi, Masayoshi. 2012. Revolution of Sensors in Micro-Electromechanical Systems. Japanese Journal of Applied Physics 51, no. 8:080001. Poly-Si surface micromachined integrated accelerometer (cross sectional structure and photographs of two-axis accelerometer). Prof. Steven S. Saliterman Esashi, Masayoshi. 2012. Revolution of Sensors in Micro-Electromechanical Systems. Japanese Journal of Applied Physics 51, no. 8:080001. 9 1/2/2017 Schematic of accelerometer with thick epitaxial poly-Si layer and photograph of resonant gyroscope. Prof. Steven S. Saliterman Esashi, Masayoshi. 2012. Revolution of Sensors in Micro-Electromechanical Systems. Japanese Journal of Applied Physics 51, no. 8:080001. Automotive sensor for yaw rate and acceleration. Prof. Steven S. Saliterman Esashi, Masayoshi. 2012. Revolution of Sensors in Micro-Electromechanical Systems. Japanese Journal of Applied Physics 51, no. 8:080001. Two-axis resonant gyroscope used for image stabilization (photograph and schematic). Prof. Steven S. Saliterman Esashi, Masayoshi. 2012. Revolution of Sensors in Micro-Electromechanical Systems. Japanese Journal of Applied Physics 51, no. 8:080001. 10 1/2/2017 Apollo 11 Gyroscope 1969 Gyroscope image courtesy of https://www.flickr.com/photos/blafetra/14524883649 Prof. Steven S. Saliterman Absolute Orientation (Euler Vector, 100Hz) Three axis orientation data based on a 360° sphere. Absolute Orientation (Quaterion, 100Hz) Four point quaternion output for more accurate data manipulation. Angular Velocity Vector (100Hz) Three axis of 'rotation speed' in rad/s. Acceleration Vector (100Hz) Three axis of acceleration (gravity + linear motion) in m/s^2. Magnetic Field Strength Vector (20Hz) Three axis of magnetic field sensing in micro Tesla (uT). Linear Acceleration Vector (100Hz) Three axis of linear acceleration data (acceleration minus gravity) in m/s^2. Gravity Vector (100Hz) Three axis of gravitational acceleration (minus any movement) in m/s^2. Temperature (1Hz) Ambient temperature in degrees celsius. Prof. Steven S. Saliterman Apollo Command Module 1973 S. Saliterman Courtesy of Adafruit Platinum resistor: ◦ Linear, stable, reproducible. ◦ Material property dependency on temperature, Thermocouples (e.g. Type K) Thermistor: a semiconductor device made of materials whose resistance varies as a function of temperature. Thermodiode and Thermotransistor. Prof. Steven S. Saliterman 11 1/2/2017 Potentiometric devices fabricated by the joining of two different metals forming a sensing junction: ◦ Based on the thermoelectric Seebeck effect in which a temperature difference in a conductor or semiconductor creates an electric voltage: D V = asD T W h ere D V is th e electrical v o ltag e, a s is the S eeb eck co efficien t ex p ressed in v o lts/K , and D T is th e tem p erature d ifferen ce ( T S - Tref ). Prof. Steven S. Saliterman Gardner, JW, VK Varadan and OO Awadelkarim, Microsensors, MEMS and Smart Devices. John Wiley & Sons, Ltd. W. Sussex (2001). When a p-n diode is operated in a constant current (IO) circuit, the forward voltage (Vout) is directly proportional to the absolute temperature (PTAT). V o ut = ö÷ k B T æç I ln çç + 1÷÷÷ q ÷ø èç I S W here k b is the B olzm an constant, T is tem peratu re, q is the charg e on an electron, I is the op eratin g current and I S is the saturation current. Prof. Steven S. Saliterman Gardner, JW, VK Varadan and OO Awadelkarim, Microsensors, MEMS and Smart Devices. John Wiley & Sons, Ltd. W. Sussex (2001). Hot wire or hot element anemometers. Calorimetric sensors. ◦ Based on convective heat exchange taking place when the fluid flow passes over the sensing element (hot body). ◦ Operate in constant temperature mode or in constant current mode. ◦ Based on the monitoring of the asymmetry of temperature profile around the hot body which is modulated by the fluid flow. Prof. Steven S. Saliterman 12 1/2/2017 The heat transferred per unit time from a resistive wire heater to a moving liquid is monitored with a thermocouple: Prof. Steven S. Saliterman Gardner, JW, VK Varadan and OO Awadelkarim, Microsensors, MEMS and Smart Devices. John Wiley & Sons, Ltd. W. Sussex (2001). In a steady state, the mass flow rate can be determined: Qm = dm Ph = (T -T ) dt cm 2 1 Where Q m is the mass flow rate, Ph is the heat transferred per unit time, c m is the specific heat capacity of the fluid and T1 ,T2 are temperature. The volumetric flow rate is calculated as follows: QV = dV Qm = dt ρm Where Q V is the volumetric flow rate, Q m is the mass flow rate and ρ m is the density. Prof. Steven S. Saliterman Prof. Steven S. Saliterman Silvestri, S. and E. Schena Micromachined Flow Sensors in Biomedical Applications. Micromachines 2012, 3, 225-243 13 1/2/2017 Cantilever type flow sensors Differential pressure-based flow sensors ◦ Measuring the drag-force on a cantilever beam. ◦ When a fluid flow passes through a duct, or over a surface, it produces a pressure drop depending on the mean velocity of the fluid. Electromagnetic Laser Doppler flowmeter ◦ The phenomenon is due to the interaction between an electromagnetic or acoustic wave and a moving object: the wave is reflected back showing a frequency different from the incident one. Lift-force and drag flow sensors Microrotor ◦ Based on the force acting on a body located in a fluid flow. ◦ Rotating turbine ◦ Temperature effects resonance frequency of a vibrating membrane. Resonating flow sensors Prof. Steven S. Saliterman Silvestri, S. and E. Schena Micromachined Flow Sensors in Biomedical Applications. Micromachines 2012, 3, 225-243 Able to Sense Direction Prof. Steven S. Saliterman Silvestri, S. and E. Schena Micromachined Flow Sensors in Biomedical Applications. Micromachines 2012, 3, 225-243 Potentiometric Sensors Voltametric Sensors ◦ Ion selective electrodes (ISE) into the nanodimension range ◦ New ion recognition chemistries ◦ New ion selective membranes ◦ Importance of the reference electrode ◦ Carbon paste electrodes (CPE) for organic molecule detection ◦ Micro and Ultramicro electrodes ◦ Environmental monitoring ◦ Carbon nanotubules ◦ Stripping voltammetry Prof. Steven S. Saliterman Privett, Benjamin J., Jae H. Shin, and Mark H. Schoenfisch. 2010. Electrochemical Sensors. Analytical Chemistry 82, no. 12:4723-4741. 14 1/2/2017 Electrochemical Biosensors Immunosensors Ion Selective Field Effect Transistors ◦ ◦ ◦ ◦ Selective and sensitive biological binding Aptamer-based biosensors Glucose, creatinine, pathologic bacteria, DNA Enzyme biosensors ◦ Bacteria, virus and cancer biomarkers ◦ Based on the electrochemical phenomena occurring within the chemically sensitive membrane placed on top of the transistor gate and on electrical transduction of the signal by this semiconductor device. Privett, Benjamin J., Jae H. Shin, and Mark H. Schoenfisch. 2010. Electrochemical Sensors. Analytical Chemistry 82, no. 12:4723-4741. Prof. Steven S. Saliterman Photocurable polymers have been used for encapsulation of ion selective field effect transistors (ISFET) and for membrane formation in chemical sensitive field effect transistors (ChemFET). D G Charge Carriers In D Charge Carriers Out G S PChannel S NChannel Shown: Insulated Gate Field-Effect Transistor (IGFET). MOSFET (metal oxide is common). Abramova, Natalia, and Andrei Bratov. 2009. Photocurable Polymers for Ion Selective Field Effect Transistors. 20 Years of Applications. Sensors 9, no. 9:7097-7110. Prof. Steven S. Saliterman Silicon (semiconductor) substrate -- - - - - + + + + + ++ + A G B S + + + ++++ + + + + - - -- -- - - D A small signal on the plate above (gate) brings electrons to the surface, allowing current to flow and amplifying the original signal. Prof. Steven S. Saliterman 15 1/2/2017 Polyimide covered by a standard photoresist and photocurable epoxy acrylate. The polymer layer after being applied to a wire bonded sensor glued to some substrate can be patterned using traditional photolithography techniques. Left: ISFET with photocurable encapsulate (1), with openings over the gate (2), contact pads (3) and scribing lines (4). Center and Right: Mounting, wire bonding and encapsulation. 3mm opening Prof. Steven S. Saliterman The best known method of ISFET membrane formation comes from traditional ion selective electrodes and is based on using a polymer matrix which is deposited over an ISFET gate and contains the required ion active components, like ionophore, plasticizer and lipophilic additives. Achievements in development of traditional ISE with liquid inner contact resulted in hundreds of different membrane compositions that can be used as well in case of ISFETs. Prof. Steven S. Saliterman Abramova, Natalia, and Andrei Bratov. 2009. Photocurable Polymers for Ion Selective Field Effect Transistors. 20 Years of Applications. Sensors 9, no. 9:7097-7110. Abramova, Natalia, and Andrei Bratov. 2009. Photocurable Polymers for Ion Selective Field Effect Transistors. 20 Years of Applications. Sensors 9, no. 9:7097-7110. Optical chemical sensors are usually configured as transducers, with transductions steps of electricaloptical-chemical-optical-electrical conversion: Prof. Steven S. Saliterman Boisde, G. and A. Harmer, Chemical and Biochemical Sensing with Optical Fibers and Waveguides, Artech House, Boston (1996) 16 1/2/2017 Esashi, Masayoshi. 2012. Revolution of Sensors in Micro-Electromechanical Systems. Japanese Journal of Applied Physics 51, no. 8:080001. Prof. Steven S. Saliterman An optical fiber consists of a solid cylindrical core of transparent material surrounded by a cladding of similar material but of lower refractive index than the core: Prof. Steven S. Saliterman The refractive index is the ratio of the speed of light in a vacuum to the speed of light in the medium: n= c vacuum ³1 c m aterial Snell’s law defines the relationship between incident and refracted light, measured as an angle from a perpendicular to the surface: n i sin I = n r sin R Prof. Steven S. Saliterman 17 1/2/2017 Glucose and anticoagulation monitoring: Prof. Steven S. Saliterman Images courtesy of LifeScan, Inc. and HemoSense, Inc. Temperature: Image courtesy of Braun Prof. Steven S. Saliterman Harsanyi, G., Sensors in Biomedical Applications, Technology and Applications. Technomic Pub. Co., Lancaster, PA (2000) Pressure: Prof. Steven S. Saliterman Fraden, J. “Noncontact temperature measurement in medicine.” Bioinstrumentation and Biosensors, D.L. Wise, Ed, Marcel Dekker (1991). 18 1/2/2017 Intraocular pressure: Prof. Steven S. Saliterman Bergveld, A.P., “The merit of using silicon for the development of hearing aid microphones and intraocular pressure sensors.” Senors and Actuators 41:42, pp. 223-229 (1994) Pulse oximetry: Prof. Steven S. Saliterman Prof. Steven S. Saliterman Parker, D. “Sensors for monitoring blood gasses in intensive care.” J Phys. E. Sci. Instrum. 20, pp. 1103-1112 (1987). 19 1/2/2017 Respiratory – spirometry and CO2: Prof. Steven S. Saliterman Implanted pacemaker and rhythm monitor: Prof. Steven S. Saliterman What are sensors and what do we sense? Sensor Classification and ideal sensor. Piezoelectric effect and SAW. MEMS & bioMEMS Thermo and thermo flow sensors Electrochemical sensors Ion Selective Field Effect Transistors Optical sensors Clinical applications Prof. Steven S. Saliterman 20