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* Minhye Chang Proceedings of the IEEE Introduction Evolution Battery-Powered BION System Applications * * Low-level electrical current to nerves or reflex centers * Triggered by • single switch(open-loop) • neuronal activity(closed-loop) * Limb loss applications • Reduce phantom pain • Restore functional movement * Introduction Evolution System Applications * Provide both stimulating and sensing capabilities * Be fully implantable * Be minimally invasive * Have real-time communication capability * Practically unlimited number of stimulation and sensing channels * Function w/o external equipment or interconnected leads btw components * Introduction Evolution System Applications * Extensive surgery •20-plus channel Nucleus FES22 requires more than 15h of surgery Infection of Large Continuous Implant Surfaces •Bacterial infection spread to the entire implant. •The only remedy is to explant the entire system. RF Powered Device Problems •Maintaining proper orientation of the power transmitting antenna •The discomfort of wearing an antenna and a battery powered transmitter Lack of Coordinated Sensors and Stimulators •Other than demand pacemakers, very few attempts to use implantable sensors Extensive Advanced Planning •Each condition usually requires a unique sensor system •The number of channels, the type of sensors and signal conditioning, and etc. Introduction Evolution System Applications * As either stimulators or sensors * Minimally invasive implantation * Wireless, real-time bidirectional communications * Flexibility and functional expandability w/o leads * A large number of channels * Self-powered operation * Introduction Evolution System Applications Battery-Powered • To improve patient acceptance • To increase the reliability • Operate for more than ten years RF-powered • Allow instantaneous control • Prevent electrostatic discharge • Need to wear an external coil * By Quallion. Capacity of 10mWH, operating at a voltage of 3.6V Introduction Evolution System Applications * For urinary incontinence * The 1st BION to have twoway telemetry * Very short time for * Wireless * Fully implantable * Data processing for sensed signals synchronization * Lack of sensing capabilities * Slow communication response time * Rechargeable * Long term immersion weakens ceramic improve longevity * Introduction Evolution System Applications * Improved IC • Increase the compliance voltage of the RF-powered microstimulator • Modified the demodulation circuit * Combining the IC and the ferrite • Longer and more efficient coil in receiving energy from the ac magnetic field * Ceramic case * Internal capacitor • Prevents continuous direct current from flowing into the tissue * Introduction Evolution System Applications * Defibrillator protection • Prevents damages from static electricity in the operating room * Eyelet • Enables a simple removal within about a week or more * Insertion System * Human experiments • 42 RF microstimulators in six stroke patients • Ultrasonic and magnetic resonance image viewing * Introduction Evolution System Applications * Stimulating lead system failure • Stimulation amplitude and low current range was unstable * Automatic tuning of AC powering coils • Need a very precise tuning frequency in coil to save • battery power A crystal controlled oscillator and a bank of about eight capacitors in the external control unit * Hermetic and electrolytic corrosion free braze joints * Introduction Evolution System Applications * Arm coil system • Microstimulators btw the wrist and elbow • To produce a magnetic field, two coil pairs are connected in series * Clinicians automatic test system • The fitting notebook station an automatic microstimulator tester • Test regime will verify nearly every connection in the microstimulator * Introduction Evolution System Applications * Introduction Evolution System Applications * • Communication and control hub • External MCU: a few controls accessible to the patient • Implantable MCU: small patient control unit (PCU) Introduction Evolution System Applications * Transmits and receives data up to 850 BPBs within 1/100s * Basic user interface • System ON/OFF control, alarms, program selection and limited parameter control * During fitting, enables the setup and the coordination * Manages the recharging subsystem * Safety mechanisms • • Emergency STOP button When BPB overheats or overcharges * Stores patient usage data and the approximate location of BPBs * Introduction Evolution System Applications * • Allows the clinician to configure and test Introduction Evolution System Applications * During the fitting, CP & MCU facilitate measurement and storage of the stimulation and sensor calibration parameters * During the stand-alone mode, essential information is stored in the MCU * Clinician’s programmer • • Gather basic personal information • • • Specify the activity sequences Establish the stimulation range and allow selection of the stimulation parameters Gather the trigger information Compose the Finite State Machine functions * Introduction Evolution System Applications * • Place the coil close to the area • Battery Depend on the frequency and stimulation levels Run in 1 to 8 days • Charging for about 5 to 20 min per day Introduction Evolution System Applications * • Transmits only power • Each BPB Charging and battery status Introduction Evolution System Applications * 12-kHz signal to generates a magnetic field * MCU • • • Determines which BPB to be charged and when to charge Indicates to the patient where the coil must be moved Selects the most discharged device * Temperature sensor that stops the process when the external coil overheating * Introduction Evolution System Applications * • Safety feature when Undesired manner No access of the patient to control unit • Magnet is positioned On the body holds off the stimulation On the other part stimulation turns on • Small, light weight, very strong magnetic signal Introduction Evolution System Applications * Introduction Evolution System Applications * Single-channel, constant- current, charge-balanced stimulator * Capacitance-coupled output prevents direct connection btw battery and tissue. * Pulse amplitude, width, and frequency * Triggering events * Dipole antenna * Crystal-controlled transmitter, receiver, & digital processing unit * Digital processing unit • • • Corrects errors in data and communication Decodes the MCU commands Generates the responses to the MCU * Introduction Evolution System Applications • • • Stimulation and/or sensing control data Forward error correction (FEC) bits • Information to MCU FEC for 1 or 2bit errors For frame synchronization and frame control data * Introduction Evolution System Applications * 10-mW-hr rechargeable lithium-ion battery * Recharging via 127kHz magnetic link * Provide 100 hours of operation * Deep discharge lifetime of more than ten years * Miniature magnetic sensor * Temperature sensor for terminating charging * Battery safety circuitry • Overvoltage, overdischarge, and overcharging * For themselves for maximum charging * Introduction Evolution System Applications * “Oscilloscope mode” during * Along the axial dimension of * Data analysis * 400~900 mmHg * AC/DC coupled * Altitude changes fitting • Count pulses: accumulated pulses every 10ms • Rectify and integrate every 10 ms the BPB reference sensor in the MCU * Introduction Evolution System Applications * Distance btw two BPBs • • • • • Intensity of the received magnetic field One BPB as a transmitter, and other BPBs as a receiver Receiver BPB detects and measures the signal strength No limit to the number of BPB receivers Measure distances btw 1~20cm * As a safety mechanism * Accurate to within 0.33˚C * Range 16~50 ˚C * Taken once per second * 8 parallel systems whose frequencies are around 127kHz * Introduction Evolution System Applications * Minimally invasive procedure A: Probe Electrode B: Dilator C: Sheath D: Ejection Tool E: 3ml Syringe • 1st test during the implantation • 2nd test right after the implantation • 3rd test one week after implantation * Introduction Evolution System Applications * * As a stimulator, biopotential signal sensor, goniometry sensor, pressure or temperature sensor • Multiple BPBs; up to 850 BPBs • Near motor-points or nerves of muscles in the arm, forearm, and hand To extend the arm and forearm, and open the hand to grasp an object • * Sensing of the muscle activities acts as triggers to other BPBs to stimulate the motor-points • * As goniometry sensors and pressure sensors Standing, ambulation, swallowing, bladder control, and respiration Measuring pressure and triggering motor-point or stopping a FES sequence • At the heel, the buttock, or hand * Introduction Evolution System Applications * As biopotential sensors * Inserted in the “stump” * Pick up motor nerve signals to control movement * Introduction Evolution System Applications * Voluntary motion is regained * * By monitoring the motor cortex By feeding back sensed response signals to the sensory cortex * Cortical interface device (CID) * * Base unit implanted in the skull monitors up to several hundred electrodes Electrode arrays placed on the sensory or motor cortices * Introduction Evolution System Applications * CID base unit • Equivalent to a group of sixty-four BPBs • Sixty-four biopotential sensing modules • Either unipolar or bipolar • Same technology developed for the BPB * Sensing electrode array • Include signal processing capability like biopotential sensing module in the BPB • same stimulation electronics like the BPB stimulation module * Introduction Evolution System Applications