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Stretchable Loudspeaker using Liquid Metal Microchannel.

Jin SW, Park J, Hong SY, Park H, Jeong YR, Park J, Lee SS, Ha JS - Sci Rep (2015)

Bottom Line: Measurements of the frequency response confirmed that the SAD was mechanically stable under both 50% uniaxial and 30% biaxial strains.Both voice and the beeping sound of an alarm clock were successfully recorded and played back through our SAD while it was attached to the wrist under repeated deformation.These results demonstrate the high potential of the fabricated SAD using Galinstan voice coil in various research fields including stretchable, wearable, and bio-implantable acoustic devices.

View Article: PubMed Central - PubMed

Affiliation: KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul, 136-701, Korea.

ABSTRACT
Considering the various applications of wearable and bio-implantable devices, it is desirable to realize stretchable acoustic devices for body-attached applications such as sensing biological signals, hearing aids, and notification of information via sound. In this study, we demonstrate the facile fabrication of a Stretchable Acoustic Device (SAD) using liquid metal coil of Galinstan where the SAD is operated by the electromagnetic interaction between the liquid metal coil and a Neodymium (Nd) magnet. To fabricate a liquid metal coil, Galinstan was injected into a micro-patterned elastomer channel. This fabricated SAD was operated simultaneously as a loudspeaker and a microphone. Measurements of the frequency response confirmed that the SAD was mechanically stable under both 50% uniaxial and 30% biaxial strains. Furthermore, 2000 repetitive applications of a 50% uniaxial strain did not induce any noticeable degradation of the sound pressure. Both voice and the beeping sound of an alarm clock were successfully recorded and played back through our SAD while it was attached to the wrist under repeated deformation. These results demonstrate the high potential of the fabricated SAD using Galinstan voice coil in various research fields including stretchable, wearable, and bio-implantable acoustic devices.

No MeSH data available.


Related in: MedlinePlus

Acoustic performance of SAD evaluated via FEM analysis.(a) Change of normalized Lorentz force (F/F0) with increase in uniaxial (red) and biaxial (blue) stretching. F0 and F are the Lorentz force before and after application of strain, respectively. (b) Change of SPL vs. frequency with change in size of liquid metal coil. Inset is the change of F/F0 with change in ratio of coil diameter to diameter of magnet. Here, red, blue, and green correspond to the inset picture of 1, 2, and 3, respectively.
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f4: Acoustic performance of SAD evaluated via FEM analysis.(a) Change of normalized Lorentz force (F/F0) with increase in uniaxial (red) and biaxial (blue) stretching. F0 and F are the Lorentz force before and after application of strain, respectively. (b) Change of SPL vs. frequency with change in size of liquid metal coil. Inset is the change of F/F0 with change in ratio of coil diameter to diameter of magnet. Here, red, blue, and green correspond to the inset picture of 1, 2, and 3, respectively.

Mentions: where P is the pressure, F is the vertical component of the Lorentz force, and A is the area of the surface. Assuming that A is a constant, P is influenced only by F. In order to estimate the effect of coil deformation on the device performance, the Lorentz forces generated upon an application of 50% uniaxial and 30% biaxial strain were calculated by finite element method (FEM) analysis. The decrease of the Lorentz force with the applied strain is expected, because the distance between the liquid-metal conductor and the center of the coil where the Nd magnet is positioned increases27. Figure 4(a) shows the change in the normalized Lorentz force (F/F0), where F0 and F are Lorentz forces before and after application of the strain, upon increasing the applied strain in uniaxial (red) and biaxial (blue) directions, respectively. F/F0 decreased by 10.7% and 17.7% under 50% uniaxial and 30% biaxial stretching, respectively. Since the rigidity of the Nd magnet was not considered for the estimation, those changes are the upper limit of the variation in the Lorentz force induced by the applied strain. Therefore, in a real situation, a much smaller strain can be applied to the central liquid-metal-injected microchannel3, which is close to the rigid magnet, forming a larger Lorentz force than that in the outer part. Even the upper-limit changes in the Lorentz force correspond simply to a difference in SPL of 1–2 dB54. Since the minimum noticeable change in SPL by the human ear is ~3 dB55, the effect of the change in the Lorentz force due to stretching deformation on the actual acoustic devices seems to be negligible. These results are consistent with the actual device performance shown in Fig. 3(c–d), where no noticeable change with both uniaxial and biaxial stretching was observed.


Stretchable Loudspeaker using Liquid Metal Microchannel.

Jin SW, Park J, Hong SY, Park H, Jeong YR, Park J, Lee SS, Ha JS - Sci Rep (2015)

Acoustic performance of SAD evaluated via FEM analysis.(a) Change of normalized Lorentz force (F/F0) with increase in uniaxial (red) and biaxial (blue) stretching. F0 and F are the Lorentz force before and after application of strain, respectively. (b) Change of SPL vs. frequency with change in size of liquid metal coil. Inset is the change of F/F0 with change in ratio of coil diameter to diameter of magnet. Here, red, blue, and green correspond to the inset picture of 1, 2, and 3, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4504143&req=5

f4: Acoustic performance of SAD evaluated via FEM analysis.(a) Change of normalized Lorentz force (F/F0) with increase in uniaxial (red) and biaxial (blue) stretching. F0 and F are the Lorentz force before and after application of strain, respectively. (b) Change of SPL vs. frequency with change in size of liquid metal coil. Inset is the change of F/F0 with change in ratio of coil diameter to diameter of magnet. Here, red, blue, and green correspond to the inset picture of 1, 2, and 3, respectively.
Mentions: where P is the pressure, F is the vertical component of the Lorentz force, and A is the area of the surface. Assuming that A is a constant, P is influenced only by F. In order to estimate the effect of coil deformation on the device performance, the Lorentz forces generated upon an application of 50% uniaxial and 30% biaxial strain were calculated by finite element method (FEM) analysis. The decrease of the Lorentz force with the applied strain is expected, because the distance between the liquid-metal conductor and the center of the coil where the Nd magnet is positioned increases27. Figure 4(a) shows the change in the normalized Lorentz force (F/F0), where F0 and F are Lorentz forces before and after application of the strain, upon increasing the applied strain in uniaxial (red) and biaxial (blue) directions, respectively. F/F0 decreased by 10.7% and 17.7% under 50% uniaxial and 30% biaxial stretching, respectively. Since the rigidity of the Nd magnet was not considered for the estimation, those changes are the upper limit of the variation in the Lorentz force induced by the applied strain. Therefore, in a real situation, a much smaller strain can be applied to the central liquid-metal-injected microchannel3, which is close to the rigid magnet, forming a larger Lorentz force than that in the outer part. Even the upper-limit changes in the Lorentz force correspond simply to a difference in SPL of 1–2 dB54. Since the minimum noticeable change in SPL by the human ear is ~3 dB55, the effect of the change in the Lorentz force due to stretching deformation on the actual acoustic devices seems to be negligible. These results are consistent with the actual device performance shown in Fig. 3(c–d), where no noticeable change with both uniaxial and biaxial stretching was observed.

Bottom Line: Measurements of the frequency response confirmed that the SAD was mechanically stable under both 50% uniaxial and 30% biaxial strains.Both voice and the beeping sound of an alarm clock were successfully recorded and played back through our SAD while it was attached to the wrist under repeated deformation.These results demonstrate the high potential of the fabricated SAD using Galinstan voice coil in various research fields including stretchable, wearable, and bio-implantable acoustic devices.

View Article: PubMed Central - PubMed

Affiliation: KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul, 136-701, Korea.

ABSTRACT
Considering the various applications of wearable and bio-implantable devices, it is desirable to realize stretchable acoustic devices for body-attached applications such as sensing biological signals, hearing aids, and notification of information via sound. In this study, we demonstrate the facile fabrication of a Stretchable Acoustic Device (SAD) using liquid metal coil of Galinstan where the SAD is operated by the electromagnetic interaction between the liquid metal coil and a Neodymium (Nd) magnet. To fabricate a liquid metal coil, Galinstan was injected into a micro-patterned elastomer channel. This fabricated SAD was operated simultaneously as a loudspeaker and a microphone. Measurements of the frequency response confirmed that the SAD was mechanically stable under both 50% uniaxial and 30% biaxial strains. Furthermore, 2000 repetitive applications of a 50% uniaxial strain did not induce any noticeable degradation of the sound pressure. Both voice and the beeping sound of an alarm clock were successfully recorded and played back through our SAD while it was attached to the wrist under repeated deformation. These results demonstrate the high potential of the fabricated SAD using Galinstan voice coil in various research fields including stretchable, wearable, and bio-implantable acoustic devices.

No MeSH data available.


Related in: MedlinePlus