Summer 2010 Research Summary

1. Summer 2010 Research Summary Sukhi Basati PhD Candidate Laboratory for Product and Process Design Director: Andreas Linninger, PhD 8/25/2010

2. Disease State - Hydrocephalus • The balance of emission and absorption of Cerebrospinal fluid (CSF) is critical for normal health. • Circumstances that lead to a disruption of this balance lead to a condition known as hydrocephalus. • Over 150,000 people are diagnosed with this disease in the U.S. each year. • Symptoms • Headache • Gait instability • Nausea • Death Leonardo da Vinci 1510 MRI and 3d reconstructions of hydrocephalic patient (right) and normal patient (left)

3. Shunt Treatment of Hydrocephalus • Solution to CSF accumulation is to remove fluid • How much? • Catheter to drain fluid • Relationship between intracranial pressure and volume • How/When does this curve change? • Continuous monitoring and treatment is done using pressure, and flow • Treatment is based on limited understanding of intracranial dynamics Integra flow valve D. A. de Jong, E.J. Delwel, J.J. Avezaat, Hydrostatic and Hydrodynamic Consideratinos in Shunted Normal Pressure Hydrocephalus. Acta Neurochirurgica. 142: 241-247, 2000. Integra Spetzler shunt for normal pressure communicating hydrocephalus

4. 3D model Design Simulation yes Fabrication analysis Bench top Analysis Animal test MRI Sensor design with geometrical constraints Image Reconstruction and 3D modeling Finite Element Simulation to analyze design Thesis Outline An Implantable System for Intracranial Volume Measurements in Hydrocephalus • Systematic approach to device design • Interdisciplinary approach • Compare experiment to simulated results • Accelerate device fabrication speed • Knowledge acquisition • Reduce animal trial and error experimentation Fabrication based on FEA simulation

5. Pre HC 3 Day 14 Day 21 Day Design and Fabrication of Sensor for Animal Measurements • Considerations: • Geometrical: electrode spacing, catheter diameter, surface area • Fabrication: cost-effective materials, scaleability

6. Towards an implantable sensor… 2 major developments of sensor fabrication: • Bonding of electrode to wire • Directly soldered • Parylene coating • Done at NCF • Polymerizes during vapor deposition • As of now, apply surfactant onto electrodes and peel off • Possible for selective deposition • More feasible approach is to apply higher viscous surfactant to electrodes and peel off. • Very biocompatible, used today in commercial medical devices

7. RMS to DC converter Voltage to Current Converter Howland current source 1 “ Sine wave oscillator Variable amp. Voltage to Current Converter Microelectronic Design • Requirements • AC signal excitation • Constant current • High SNR • Data acquisition DC to DC converter Provides constant power Sine Wave Generator 1 Khz 10 μA peak-peak 1 Power 4 Inst. Amp G = Variable 8 mV Datalogger /Labview Sampling Rate = 1000 Hz 2 Differential Amplifier Gain = 68 (0.4 * 68) mV 19.2 mV 3 • Advantages • Adjustable current source • Adjustable frequency • Adjustable gain • Modifiable design • Future MCU incorporation 7.6 mV Microcontroller (Power control + Digital signal out to RF transmitter) RMS – DC Converter • Computer Layout • Through hole components • Future SMT design

8. Development of the electronics… ;*******Main loop banksel GPIO ;turn on LED bsf GPIO,nLED movlw 500 ;try to stay on for 5 s. there is an error here - watch when you build project call meas_del ;delay banksel GPIO ;turn off LED bcf GPIO,nLED sleep ;enter sleep mode (until WDT time-out) goto loop ;repeat forever ;****subroutine meas_del ;measure input on GP0 BSF ADCON0, GO ;Start Conversion BTFSC ADCON0,GO ;is conversion done? GOTO $-1 ;no test again BANKSEL ADRESH MOVF ADRESH,W ;read upper two bits MOVWF RESULTHI ;Store in GPR Space BANKSEL ADRESL MOVF ADRESL,W ;Read lower 8 bits MOVWF RESULTLO ;Store in GPR Space ;delay W x 10 ms movwf dc3 ;delay = 1+Wx(3+10009+3)-1+4 dly2 movlw .17 ;repeat inner loop 17 itmes ;if longer power on increase but WDT decreases movwf dc2 ;13x(767+3)-1 = 10009 cycles clrf dc1 ;inner loop = 256x3-1 dly1 decfsz dc1, f goto dly1 decfsz dc2,f ;end middle loop goto dly1 decfsz dc3,f ;end outer loop goto dly2 return END • Switched from Basic Stamp to PIC microcontroller • Programmed PIC12F683 in assembly; learning C • Successfully programmed on-off control using sleep function • Power saving, drift reduction • Psuedo-Code: • Wake up from sleep mode for 10 seconds • Output high on two pins • Read analog voltage on one pin and store value • Send serial data of voltage to external RF transmitter • Go into sleep mode for 1 minute PC (program µC) Programmer (download code to µC) Test (breadboard (LED))

9. Auxiliary tasks: • REU Advising • LPPD Computer Administrator Review of Summer 2010 Semester • There were 3 main projects • Present Preliminary Defense (100%) • Priority: High • Write Draft with Michael on Acute Measurements of Volume in HC Animal (75%) • Repeated Measurements with Emily • Need to perform analysis of data • Priority: Medium • Design Surface Mount Microeletronic Unit (100%) • Created Three Dimensional Representation • Obtained Dimensions (1” x 1.5”) • Priority: Medium

10. Proposed Fall 2010 Plans • Submit Rat HC Measurement Paper to JNS-Pediatrics • Priority: Medium • Fabricate Microelectronic Unit for Long Term Measurements • Priority: High • Perform Sensor Simulations (Positional Dependence) • Priority: Medium • Submit Grant • Priority: High