Magnetic Sensors on Flexible Substrates

11/12/2019

Magnetoresistive sensors have attracted much interest in the past decades due to their high sensitivity, low cost and power consumption and small size. In order to achieve the same functionality on flexible substrates as on rigid, the magnetoelastic properties of thin films and deformability of polymers must be understood in depth. In this work we study the optimization of the microfabrication process of anisotropic magnetoresistive sensors on flexible substrates. Two different polymers were used, namely Polyimide (25 and 125 µm) and Polyethylene naphtalate and also two ferromagnetic alloys were deposited as thin films. The asdeposited materials are studied for their crystalline and magnetic properties, using X-ray diffraction and Vibrating Sample Magnetometer techniques. The structures design has been optimized throughout the fabrication, as obstacles appear, and SEM imaging is used to identify defects in the fabricated structures. Five samples were successfully fabricated and their magneto-transport properties were measured through a custom bending setup integrated on the existing apparatus at INESC-MN. A maximum AMR ratio of 0.90% was accomplished, which is very close to silicon counterparts. PI-125 µm seems to be the best substrate for the sensor layer, as it yielded better AMR signal, it has the drawback of not reaching the same curvature as easily as PEN-75 µm and PI-25 µm. The thinner polyimide shows the lowest AMR ratio, but on the other hand it also presents the lowest saturation field and stress values, with the advantage of conforming to almost any shape.

Authors in the community:

• 

  A

  Ana Catarina Rosa Janeiro

  ist178306

Supervisors of this institution:

• 

  D

  Diana Cristina Pinto Leitão

  ist18063

mechanical-engineering - Mechanical engineering

por - Portuguese

Instituto Superior Técnico