Biomechanical Tissue Stimulator Group 1: Matt Brady (BME/EE) Ankeet Choxi (BME) Misha Kotov (CS) Steven Manuel (ME) Adviser: Dr. V. Prasad Shastri

Overview  Design device that mimics physiological cyclic compressive loading to induce growth repair and remodeling mechanisms during tissue culture of articular cartilage

What are we stimulating?  Articular cartilage covers human joint surfaces transfers mechanical load to skeletal system makes up ~2% of tissue volume in human body

Persistent medical problems  Limited ability to self-repair avascular  Osteoarthrosis and related problems very common  100,000 AC injuries annually  Arthritis 2 nd most common US disability $86 billion in medical expenses annually  21% of adults in US diagnosed with arthritis  Very marketable project

Why stimulate culturing cartilage?  Hypothesized that mechanically stimulated cartilage will grow more like in vivo cartilage Increased formation of cartilage matrix, stronger  Type II collagen  Glycosaminoglycan (GAG)

Past Work Ongoing cell-culture research project Prototype of stimulator has been constructed Many problems incurred Much research done for design of new device Range of force Sensors Detection and environment

Current Work  Waiting on sensors, driver, and power supply to arrive  Finishing up milling of our device frame and constructing our frame.  Continuing to write pseudo-code until all of our parts arrive.

Design Parameters  Accuracy of 20 microns  Stimulation frequency of 1 Hz max  Max load of 1 MPa or 100 N per sample  12 wells at once  Max in-test stroke of 1 mm  Total sample size of 10 mm  100 percent humidity at 98°F  Use multiple waveforms for stimulation

Finite Element Analysis  Completed finite element analysis and finalized fabrication parameters

Contact Sensor  Made significant progress toward an easy to fabricate custom contact sensor

computer DAQ Card Tissue Stimulator Displacement Sensors Driver Power Supply Contact Sensors

Programming objectives  Program an application provide the following: Control the stepper motor Initialize and calibrate the sensors Establish a baseline for measurements Gather relevant data

Application considerations  Precise motion control for the motor  Display the baseline displacement where contact is made with all wells; record measurements in reference to this point  Ideally, allow for customized routines, be able to save and repeat procedures  Update experiment figures in real time  Provide exception handling routines  Communication with standalone control unit

Current Work on Programming  Working to modify some pre- programmed modules to control stepper motor  Contacted our assigned application engineer from National Instruments  Set up the DAQ card and installed relevant software  Working on building application

DAQ Card  Reads data from the motor and sensors  Keeps timing of device  Outputs the step and direction into the driver which runs the motor  Runs off LabView

Motor Driver  Driver takes inputs from the DAQ card and relays them to the motor  Allows fractional stepping of motor  Provides current limiting to keep motor from getting too hot and drawing too much power

Power Supply  Regulated 27V so motor runs at optimal current  Connects to driver, which in turn powers motor  Powers other components as well, however, resistors need to be used to lower voltage.

Displacement Sensor  Linear Encoder  Will output measurements of displacement  Needed to determine amount of strain applied to each tissue sample  Used as a tilt sensor (3 sensors)

Future Work  Finishing milling and construction of device frame.  Program common compatibility of motors, sensors, drivers, and power supply.  Begin phase testing with sensors and other components

Summary  Articular cartilage and problems  Biomechanical tissue stimulator Mechanically stimulates cartilage Promotes growth of tissue  Design, considerations

End Goals  End Goal of Overall Project To develop implantable artificial cartilage to replace damaged articular cartilage in the body.  End Goal of Senior Design Project To develop device that mimics mechanical load placed on growing cartilage through controlled experimental stimulation.

References Aufderheide, Adam C., Athanasiou, Kyriacos A. A Direct Compression Stimulator for Articular Cartilage and Meniscal Explants. (2006) Annals of Biomedical Engineering, Vol Bobic,Vladimir. Current Status of the Articular Cartilage Repair biomed: The Journal of Regenerative Medicine Apr 2000, Vol. 1, No. 4: Mansour JM. Biomechanics of Cartilage. (2004) Kinesiology: The Mechanics & Pathomechanics of Human Movement by Carol Oatis Xia Y, Moody JB, Alhadlaq H. Orientational Dependence of T2 Relaxation in Articular Cartilage: a microscopic MRI study. (2002) Magnetic Resonance in Medicine 48: