# Design and optimization of arrays of neodymium iron boron-based magnets for magnetic tweezers applications

## Abstract

We present the design methodology for arrays of neodymium iron boron (NdFeB)-based magnets for use in magnetic tweezers devices. Using finite element analysis (FEA), we optimized the geometry of the NdFeB magnet as well as the geometry of iron yokes designed to focus the magnetic fields toward the sample plane. Together, the magnets and yokes form a magnetic array which is the basis of the magnetic tweezers device. By systematically varying 15 distinct shape parameters, we determined those features that maximize the magnitude of the magnetic field gradient as well as the length scale over which the magnetic force operates. Additionally, we demonstrated that magnetic saturation of the yoke material leads to intrinsic limitations in any geometric design. Using this approach, we generated a compact and light-weight magnetic tweezers device that produces a high field gradient at the image plane in order to apply large forces to magnetic beads. We then fabricated the optimized yoke and validated the FEA by experimentally mapping the magnetic field of the device. The optimization data and iterative FEA approach outlined here will enable the streamlined design and construction of specialized instrumentation for force-sensitive microscopy.

- Authors:

- Department of Mechanical Engineering and Materials Research Laboratory, University of California, Santa Barbara, California 93106 (United States)

- Publication Date:

- OSTI Identifier:
- 22392500

- Resource Type:
- Journal Article

- Journal Name:
- Review of Scientific Instruments

- Additional Journal Information:
- Journal Volume: 86; Journal Issue: 5; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0034-6748

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; BORON; DESIGN; FINITE ELEMENT METHOD; GEOMETRY; IRON; ITERATIVE METHODS; LENGTH; MAGNETIC FIELDS; MAGNETS; MICROSCOPY; NEODYMIUM; OPTIMIZATION

### Citation Formats

```
Zacchia, Nicholas A., and Valentine, Megan T.
```*Design and optimization of arrays of neodymium iron boron-based magnets for magnetic tweezers applications*. United States: N. p., 2015.
Web. doi:10.1063/1.4921553.

```
Zacchia, Nicholas A., & Valentine, Megan T.
```*Design and optimization of arrays of neodymium iron boron-based magnets for magnetic tweezers applications*. United States. doi:10.1063/1.4921553.

```
Zacchia, Nicholas A., and Valentine, Megan T. Fri .
"Design and optimization of arrays of neodymium iron boron-based magnets for magnetic tweezers applications". United States. doi:10.1063/1.4921553.
```

```
@article{osti_22392500,
```

title = {Design and optimization of arrays of neodymium iron boron-based magnets for magnetic tweezers applications},

author = {Zacchia, Nicholas A. and Valentine, Megan T.},

abstractNote = {We present the design methodology for arrays of neodymium iron boron (NdFeB)-based magnets for use in magnetic tweezers devices. Using finite element analysis (FEA), we optimized the geometry of the NdFeB magnet as well as the geometry of iron yokes designed to focus the magnetic fields toward the sample plane. Together, the magnets and yokes form a magnetic array which is the basis of the magnetic tweezers device. By systematically varying 15 distinct shape parameters, we determined those features that maximize the magnitude of the magnetic field gradient as well as the length scale over which the magnetic force operates. Additionally, we demonstrated that magnetic saturation of the yoke material leads to intrinsic limitations in any geometric design. Using this approach, we generated a compact and light-weight magnetic tweezers device that produces a high field gradient at the image plane in order to apply large forces to magnetic beads. We then fabricated the optimized yoke and validated the FEA by experimentally mapping the magnetic field of the device. The optimization data and iterative FEA approach outlined here will enable the streamlined design and construction of specialized instrumentation for force-sensitive microscopy.},

doi = {10.1063/1.4921553},

journal = {Review of Scientific Instruments},

issn = {0034-6748},

number = 5,

volume = 86,

place = {United States},

year = {2015},

month = {5}

}