Glass Microbubble Encapsulation for Improving the Lifetime of a Ferrofluid-Based Magnetometer
In this paper, we explore the use of chip-scale blown glass microbubble structures for MEMS packaging applications. Specifically, we demonstrate the efficacy of this method of packaging for the improvement of the lifetime of a ferrofluid-based magnetoviscous magnetometer. We have previously reported...
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MDPI AG
2025-04-01
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| author | Chenchen Zhang Srinivas Tadigadapa |
| author_facet | Chenchen Zhang Srinivas Tadigadapa |
| author_sort | Chenchen Zhang |
| collection | DOAJ |
| description | In this paper, we explore the use of chip-scale blown glass microbubble structures for MEMS packaging applications. Specifically, we demonstrate the efficacy of this method of packaging for the improvement of the lifetime of a ferrofluid-based magnetoviscous magnetometer. We have previously reported on the novel concept of a ferrofluid based magnetometer in which the viscoelastic response of a ferrofluid interfacial layer on a high frequency shear wave quartz resonator is sensitively monitored as a function of applied magnetic field. The quantification of the magnetic field is accomplished by monitoring the at-resonance admittance characteristics of the ferrofluid-loaded resonator. While the proof-of-concept measurements of the device have been successfully made, under open conditions, the evaporation of the carrier fluid of the ferrofluid continuously changes its viscoelastic properties and compromises the longevity of the magnetometer. To prevent the evaporation of the ferrofluid, here, we seal the ferrofluid on top of the micromachined quartz resonator within a blown glass hemispherical microbubble attached to it using epoxy. The magnetometer design used a bowtie-shaped thin film Metglas (Fe<sub>85</sub>B<sub>5</sub>Si<sub>10</sub>) magnetic flux concentrator on the resonator chip. A four-times smaller noise equivalent, a magnetic field of 600 nT/√Hz at 0.5 Hz was obtained for the magnetometer using the Metglas flux concentrator. The ferrofluid-based magnetometer is capable of sensing magnetic fields up to a modulation frequency of 40 Hz. Compared with the unsealed ferrofluid device, the lifetime of the glass microbubble integrated chip packaged device improved significantly from only a few hours to over 50 days and continued. |
| format | Article |
| id | doaj-art-bf011e5ffa0e4a08bd37b37b85be5088 |
| institution | Kabale University |
| issn | 2072-666X |
| language | English |
| publishDate | 2025-04-01 |
| publisher | MDPI AG |
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| series | Micromachines |
| spelling | doaj-art-bf011e5ffa0e4a08bd37b37b85be50882025-08-20T03:48:01ZengMDPI AGMicromachines2072-666X2025-04-0116551910.3390/mi16050519Glass Microbubble Encapsulation for Improving the Lifetime of a Ferrofluid-Based MagnetometerChenchen Zhang0Srinivas Tadigadapa1Materials Research Institute, Department of Electrical Engineering, Penn State University, University Park, PA 16802, USAMaterials Research Institute, Department of Electrical Engineering, Penn State University, University Park, PA 16802, USAIn this paper, we explore the use of chip-scale blown glass microbubble structures for MEMS packaging applications. Specifically, we demonstrate the efficacy of this method of packaging for the improvement of the lifetime of a ferrofluid-based magnetoviscous magnetometer. We have previously reported on the novel concept of a ferrofluid based magnetometer in which the viscoelastic response of a ferrofluid interfacial layer on a high frequency shear wave quartz resonator is sensitively monitored as a function of applied magnetic field. The quantification of the magnetic field is accomplished by monitoring the at-resonance admittance characteristics of the ferrofluid-loaded resonator. While the proof-of-concept measurements of the device have been successfully made, under open conditions, the evaporation of the carrier fluid of the ferrofluid continuously changes its viscoelastic properties and compromises the longevity of the magnetometer. To prevent the evaporation of the ferrofluid, here, we seal the ferrofluid on top of the micromachined quartz resonator within a blown glass hemispherical microbubble attached to it using epoxy. The magnetometer design used a bowtie-shaped thin film Metglas (Fe<sub>85</sub>B<sub>5</sub>Si<sub>10</sub>) magnetic flux concentrator on the resonator chip. A four-times smaller noise equivalent, a magnetic field of 600 nT/√Hz at 0.5 Hz was obtained for the magnetometer using the Metglas flux concentrator. The ferrofluid-based magnetometer is capable of sensing magnetic fields up to a modulation frequency of 40 Hz. Compared with the unsealed ferrofluid device, the lifetime of the glass microbubble integrated chip packaged device improved significantly from only a few hours to over 50 days and continued.https://www.mdpi.com/2072-666X/16/5/519glass microbubblechip-scale packagingquartz resonatorMetglasmagnetometer |
| spellingShingle | Chenchen Zhang Srinivas Tadigadapa Glass Microbubble Encapsulation for Improving the Lifetime of a Ferrofluid-Based Magnetometer Micromachines glass microbubble chip-scale packaging quartz resonator Metglas magnetometer |
| title | Glass Microbubble Encapsulation for Improving the Lifetime of a Ferrofluid-Based Magnetometer |
| title_full | Glass Microbubble Encapsulation for Improving the Lifetime of a Ferrofluid-Based Magnetometer |
| title_fullStr | Glass Microbubble Encapsulation for Improving the Lifetime of a Ferrofluid-Based Magnetometer |
| title_full_unstemmed | Glass Microbubble Encapsulation for Improving the Lifetime of a Ferrofluid-Based Magnetometer |
| title_short | Glass Microbubble Encapsulation for Improving the Lifetime of a Ferrofluid-Based Magnetometer |
| title_sort | glass microbubble encapsulation for improving the lifetime of a ferrofluid based magnetometer |
| topic | glass microbubble chip-scale packaging quartz resonator Metglas magnetometer |
| url | https://www.mdpi.com/2072-666X/16/5/519 |
| work_keys_str_mv | AT chenchenzhang glassmicrobubbleencapsulationforimprovingthelifetimeofaferrofluidbasedmagnetometer AT srinivastadigadapa glassmicrobubbleencapsulationforimprovingthelifetimeofaferrofluidbasedmagnetometer |