# Characterization and Clinical Trial of an Innovative High-Speed Lancing Device
## 2 Experimental Details  
### Lancing Device Principle  
The internal structure of a conventional lancing device comprises a main carrying pillar, a lancet holder and a spring. The compressive force of the spring is used to generate a puncture force. To prevent the lancet from moving as the spring vibrates, the spring of the new lancing device is separated from the lancet holder. The major difference from the conventional lancing device is that the front end of its main carrying pillar is attached to an iron cube of greater mass, which is also connected to the spring to form a single structure. Figure 1 compares the internal structures of the conventional lancing device and the high-speed lancing device. As presented in Figure 1, the high-speed lancing device is designed with its spring separate from its lancet, and an iron cube of greater mass is attached to the spring. The metallic block has a mass of 1.2 g, and the lancet holder has a mass of 0.54 g. The specifications of its spring are those of the marketed lancing device, whose spring is made of piano wire, with a wire diameter of 0.6 mm, an outer diameter of 6.1 mm, an effective coil number of 20, a free length of 32 mm, a \(k\) value of 0.113 kgf/mm, and a required load force of 1.2 kgf. The conventional device used in this study is Sterolance (SHILI Co., Ltd., Taiwan). The lancet used in the high-speed lancing device has the same specifications as the commercially available lancing device, and both are Easy Touch 28 gauge lancets (MHC Medical Products, Fairfield, OH, USA). Figure 1: Comparison of main internal structures of conventional lancing device and high-speed lancing device. After the high-speed lancing device picks a finger, its iron cube instantly strikes the lancet holder. From one-dimensional elastic collision theory, Equation (1) gives the velocity of the iron cube (\(v1^{\prime}\)) and the velocity of lancet holder (\(v2^{\prime}\)) after striking. \[\left\{ \begin{array}{c}\vskip 3.0 pt plus 1.0 pt minus 1.0 pt\gamma_{1}^{\prime}=\frac{m_{1}-m_{2}}{m_ {1}+m_{2}}v_{1}+\frac{2m_{1}}{m_{1}+m_{2}}v_{2}\\ \vskip 3.0 pt plus 1.0 pt minus 1.0 pt\gamma_{2}^{\prime}=\frac{2m_{1}}{m_{1}+m_{2}}v_{1}- \frac{m_{1}-m2}{m_{1}+m_{2}}v_{2}\end{array} \right. \tag{1}\]  
Under the special conditions of elastic collision, the following three situations may pertain. 1. If \(m1=m2\), then \[\left\{ \begin{array}{c}\vskip 3.0 pt plus 1.0 pt minus 1.0 pt\
u_{1}^{\prime}\cong v_{1}\\ \vskip 3.0 pt plus 1.0 pt minus 1.0 pt\
u_{2}^{\prime}\cong 2v_{1}\end{array} \right.\] (2)
2. If \(m1>m2\) and \(v2=0\), then \[\left\{ \begin{array}{c}\vskip 3.0 pt plus 1.0 pt minus 1.0 pt\
u_{1}^{\prime}=\frac{m_{1}-m_{2}}{m_ {1}+m_{2}}v_{1}+\frac{2m_{1}}{m_{1}+m_{2}}v_{2}\\ \vskip 3.0 pt plus 1.0 pt minus 1.0 pt\
u_{2}^{\prime}=\frac{2m_{1}}{m_{1}+m_{2}}v_{1}- \frac{m_{1}-m2}{m_{1}+m_{2}}v_{2}\end{array} \right.\] (3) If \(m1>>m2\) and \(v2=0\), then \[\left\{ \begin{array}{c}\vskip 3.0 pt plus 1.0 pt minus 1.0 pt\
u_{1}^{\prime}\cong v_{1}\\ \vskip 3.0 pt plus 1.0 pt minus 1.0 pt\
u_{2}^{\prime}\cong 2v_{1}\end{array} \right.\] (4)  
From supposition (3) above, if the mass (\(m1\)) of the iron cube (impactor) considerably exceeds that of the lancet holder (\(m2\)), then after striking, the velocity of lancet holder is close to double the velocity of the conventional lancing device, implying that the lancet of the high-speed lancing device exhibits high-speed motion. Since the spring and the lancet holder are designed to be separate, after the lancing device strikes a finger, its lancet is not affected by the to-and-fro vibration of the spring, and so it pierces the skin only once. Therefore, the duration of the lancet in the skin can be greatly shortened, and the pain is greatly reduced. In this work, an accelerometer is used to measure the slight motion of the lancet, and acquisition schemes are used to obtain its acceleration.