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. 2016 Sep 20;16(9):1533.
doi: 10.3390/s16091533.

Fabrication of Micro-Needle Electrodes for Bio-Signal Recording by a Magnetization-Induced Self-Assembly Method

Keyun Chen  1 , Lei Ren  2 , Zhipeng Chen  3 , Chengfeng Pan  4 , Wei Zhou  5 , Lelun Jiang  6
Affiliations

Fabrication of Micro-Needle Electrodes for Bio-Signal Recording by a Magnetization-Induced Self-Assembly Method

Keyun Chen et al. Sensors (Basel). .

Abstract

Micro-needle electrodes (MEs) have attracted more and more attention for monitoring physiological electrical signals, including electrode-skin interface impedance (EII), electromyography (EMG) and electrocardiography (ECG) recording. A magnetization-induced self-assembling method (MSM) was developed to fabricate a microneedle array (MA). A MA coated with Ti/Au film was assembled as a ME. The fracture and insertion properties of ME were tested by experiments. The bio-signal recording performance of the ME was measured and compared with a typical commercial wet electrode (Ag/AgCl electrode). The results show that the MA self-assembled from the magnetic droplet array under the sum of gravitational surface tension and magnetic potential energies. The ME had good toughness and could easily pierce rabbit skin without being broken or buckling. When the compression force applied on the ME was larger than 2 N, ME could stably record EII, which was a lower value than that measured by Ag/AgCl electrodes. EMG signals collected by ME varied along with the contraction of biceps brachii muscle. ME could record static ECG signals with a larger amplitude and dynamic ECG signals with more distinguishable features in comparison with a Ag/AgCl electrode, therefore, ME is an alternative electrode for bio-signal monitoring in some specific situations.

Keywords: ECG; EMG; electrode; impedance; insertion; magnetization-induced self-assembling; micro-needle array.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Interface between skin and: (a) wet electrode; and (b) ME.
Figure 2
Figure 2
ME fabrication process: (a) The magnetization-induced MA equipment; (b) MA formation by MSM; (c) Sputtering coating Ti/Au films on the surface of MA; and (d) rendered image of ME.
Figure 3
Figure 3
Schematic illustration of (a) fracture; and (b) insertion test ex vivo.
Figure 4
Figure 4
Setup designed for EII recording during the insertion process.
Figure 5
Figure 5
EMG recorded by: (a) Ag/AgCl electrodes; and (b) ME; (c) Recording positions.
Figure 6
Figure 6
(a) ME and Ag/AgCl electrode; (b) SEM image of MA; (c) micro-needle; (d) micro-needle tip; (e) micro-needle bottom; and (f) micro-needle middle.
Figure 7
Figure 7
(a) Resistance force during the fracture test; and (b) SEM images of bent MEs after the fracture test.
Figure 8
Figure 8
(a) Insertion force vs. displacement curve; (b) the penetration point; and (c) fluorescence image of punctured rabbit skin.
Figure 9
Figure 9
Insertion force and EII test. (a) EII during the insertion process; and (b) EII under different input voltage frequency.
Figure 10
Figure 10
ECG signals recorded by Ag/AgCl electrodes and ME in the (a) static state; and (b) dynamic state.
Figure 11
Figure 11
Frequency spectrum of ECG signals recorded by Ag/AgCl electrode and ME: (a,c) at the static state; and (b,d) at the dynamic state.
See this image and copyright information in PMC

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