Piezoresistive strain concentrator

A piezoresistive device for sensing mechanical input and converting mechanical movement of at least two relatively movable parts into electrical output, comprising:

• a substrate of SOI;
• a gap extending across a portion of the substrate defining the at least two relatively moveable parts and a flexible cross-section that connects the at least two relatively moveable parts, the cross-section being made of a same material as the substrate;
• at least two strain sensitive elements at a surface of the substrate and connected in series, each of the at least two strain sensitive elements having two end portions interconnected by an intermediate neck portion, each neck portion being supported on a corresponding structure that concentrates strain, the corresponding structure extending across the gap and having vertical walls extending to the cross-section in the gap, the corresponding structure being made of the same material as the substrate;
• and
• at least one electrode electrically connected to the end portions configured to detect changes in an electrical resistance between the end portions when the neck portions are subjected to stress in a direction of a current through the at least two strain sensitive elements that results from a relative movement of the at least two relatively moveable parts.

A piezoresistive device for sensing mechanical input and converting mechanical movement of at least two relatively movable parts into electrical output, comprising:

• a substrate of SOI;
• a triple-bossed diaphragm on one side of the substrate, the triple-bossed diaphragm having a rim, a diaphragm extending across the rim, a central boss and two outer bosses on either side of the central boss and inside of the rim;
• four gaps extending across a portion of the substrate defining the at least two relatively moveable parts and flexible cross-sections extending between corresponding gaps such that two of the gaps are located outside the outer bosses and two of the gaps are located on either side of the central boss and inside of either outer boss;
• four strain sensitive element pairs provided at a surface of the substrate around the gaps, each pair having two strain sensitive elements connected in a series, each of a strain sensitive element having two end portions interconnected by an intermediate neck portion, the neck portion being supported on a corresponding structure that concentrates strain, the corresponding structure extending across the gap and having vertical walls extending to the cross-section in the corresponding gap, the four strain sensitive element pairs connected as a bridge circuit;
• and
• electrical connections to the bridge circuit configured to measure an unbalance resulting from changes in a resistance of the four strain sensitive element pairs caused by tilting of the outer bosses in response to pressure applied perpendicular to the device.