A magnetic gradiometer device based on magnetic tunneling junctions for use in detection and measurement of structural integrity, inhomogeneities, and magnetic properties of magnetic materials including magnetic cement over large standoff distances

Magnetic Gradiometer Device Based on Magnetic Tunneling


Nondestructive testing (NDT) is widely used in industry for noninvasive inspection, diagnosis, and evaluation of materials for defects. Our novel magnetic gradiometer can be used for detection and measurement of structural integrity, inhomogeneities, and magnetic properties of magnetic materials, including magnetic cement, over large standoff distances. Its state-of-the-art magnetic tunneling junction sensors offer high performance, high temperature operation, and a fabrication process compatible with silicon circuit technology.

 Market Opportunity

Magnetic materials, e.g., ferrous metals, are prevalent in infrastructure projects and the energy industry. Cement , for example, can become weakly magnetic if magnetic powders are impregnated into the cement. The structural integrity of cement in oil wells, in particular, is critically important to public safety and the environment. In fact, the 2010 Deepwater Horizon oil spill, regarded as one of the largest environmental and economic disasters in the U.S., was caused by defective cement. Common NDT methods include Eddy-current testing, used for nonferrous conductors, and magnetic flux leakage, used in the vicinity of cracks in ferromagnetic materials. Thus there is a need for a sensitive NDT method for use with magnetic materials.

 Innovation and Meaningful Advantages

Our diagnostics-while-drilling (DWD) provides real-time information from the downhole environment in the oil field, allowing the driller to make fast decisions. The magnetic gradiometer can detect structural defects in cement in the well, allowing the driller to repair the defects and prevent oil spill disasters. Data provided from DWD systems also provide researchers with valuable high-fidelity data sets that improve understanding of the drilling. 

The compact gradiometer can be used to make an instrument (handheld or otherwise) to measure the magnetic properties, such as magnetic susceptibility, of a magnetic material without touching the sample. It can detect defects over large distances and is extremely sensitive and immune to harsh environments. It can also be used to inspect the uniformity or inhomogeneity of a magnetic material. The instrument can be used for scientific research on magnetic materials and samples, inspection, quality control, and failure analysis of products and prototypes.

Collaboration Opportunity

We are interested in exploring 1) startup opportunities with investors; 2) research collaborations with leading companies to develop this technology; and 3) licensing opportunities with companies.

Principal Investigator

Gang Xaio, PhD

Professor of Physics and Engineering,

Brown University

Brown Tech ID #3075


IP Website

IP Information

2022-02-10 WO2022032852A1; published.


Egelhoff WF Jr, Höink VE, Lau JW, Shen WF, Schrag BD, Xaio G. Magnetic tunnel junctions with large tunneling magnetoresistance and small saturation fields. Journal of Applied Physics 2010;107;09C705 2010. doi.org/10.1063/1.3358609

Contact Information

Brian Demers

Director of Busniess Development

Physical & Computational Sciences


Patent Information:
For Information, Contact:
Brown Technology Innovations
350 Eddy Street - Box 1949
Providence, RI 02903
Gang Xiao
Guanyang He
Yiou Zhang
Xixiang Zhang
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