The graphs above demonstrate some of the design limitations of microsensor technology. Figure on the left shows a common intravascular stent implantation procedure for higher severity stenotic lesions. The metal stent surrounds the deflated balloon catheter (green) which, in turn, sits on top of the guide wire (red). In order to confirm re-establishment of blood flow past the lesion site, pressure, flow and temperature sensors would need to fit inside a 0.36 mm diameter wire shown on the right. This constitutes a significant design challenge and one that has just recently been overcome by new sensor fabrication protocols discussed below.    

The figures above show a blow up view of an early microsensor based on a deflectable polysilicon diaphragm and a free-hanging polysilicon piezoresistor that changes resistance in response to torque-induced strain (right). The electrical bonding pads behind the piezoresistor attachment point send current in order to monitor the strain induced changes in resistance and feedback the signal along the length of the wire to an external source. The width and height of the chip overall are less than 0.2 mm which allows the chip to be secured to the 0.36 mm diameter guide wire.

This shows an SEM micrograph of the chip that is integrated into the flexible guide wire mesh design.