Newsletter  2018.1  Index

Theme : "Mechanical Engineering Congress, 2017 Japan (MECJ-17)" Preface M. MOTOZAWA, S. KUROSAWA Research Progress of Functional Fluids Engineering Hideya NISHIYAMA (Tohoku University) Heat transfer enhancement and drag reducing methods inspired by the skin surfaces of dolphins Yoshimichi HAGIWARA (Kyoto Institute of Technology) On the injection depth of the laser-induced microjet into the soft material Nanami ENDO, Sennosuke KAWAMOTO, Yoshiyuki TAGAWA (Tokyo University of Agriculture and Technology) Cavitation onset induced by sudden acceleration Akihito KIYAMA (Tokyo University of Agriculture and Technology), Zhao Pan (Utah State University), Yoshiyuki TAGAWA (Tokyo University of Agriculture and Technology), Jesse Daily (Naval Undersea Warfare Center), Scott Thomson (Brigham Young University), Randy Hurd, Tadd Truscott (Utah State University) Investigation of the sustaining mechanism of turbulence of Newtonian fluids by using viscoelastic fluids Yasufumi HORIMOTO, Susumu GOTO (Osaka University)

 

On the injection depth of the laser-induced microjet into the soft material

Nanami ENDO Sennosuke Kawamoto, Yoshiyuki TAGAWA Tokyo University of Agriculture and Technology

Abstract

Recently, a laser-induced microjet is expected to be applied to the needle-free injection devices due to its unique highly-focused jet shape. The highly-focused microjet is generated by irradiating a liquid filled in a capillary tube with a pulsed laser. Considering practical use of the needle-free injection, we should control the injection depth. Although the microjet injection phenomena into a model material of the skin have been studied, the effect of the distance L where a microjet travels before impacting at a soft material on injection depth Di have not been researched. The distance L is not a parameter which controls the jet generation, but it is necessary to know appropriate value of the distance L in order to determine the condition of use of the injection system. We investigate experimentally the effect of the distance L where a microjet travels before impacting at a soft material on injection depth Di. As a soft material, we used 5wt% gelatin. We clarify the trend that, with increase of the distance L, the injection depth Di increases, obtains a peak value, and then decreases. Furthermore, experimental results suggest that the focused jet shape is important for jet injection. Additionally, we consider what determines the distance Lpeak at which the injection depth Di obtains a peak value. Based on scaling argument using the focusing time scaleﾎ杯f estimated by the initial velocity U0 of free surface and the curvature radius r, we find that r has a great influence on the distance Lpeak. In order to verify this, we normalize the result of the injection experiments with the capillary tubes of various inner diameter d. The normalized result indicate that the distance Lpeak depend on the curvature radius r.

 

Key words

Laser-induced microjet, Needle-free injection, Injection depth, Jet shape, Travering distance

 

Figures

Fig. (a) Side view of a capillary tube and a container filled with gelatin. The sketch shows definition of experimental parameters. (b) One example of a series of snapshots taken by high-speed camera. The microjet travels from bottom to up and injects into gelatin.