Fabrication Of Humidity Microsensor Based On Laser Micromachining Technology

Accurate and rapid humidity detection has great value in aerospace,clinical diagnosis,environmental monitoring,drug transportation and storage,biochemical detection and other fields.But the traditional process of fabricating humidity sensor is complex and expensive.Laser induced forward transfer technology has many advantages,such as flexibility,adaptability,high machining accuracy,low cost and environmental-friendly.It has great prospect in microelectronic preparation.However,the laser induced forward transfer technology still has some problems,such as the inaccurate donor film thickness and unstable transfer process,which leads to quality defects.For this reason,laser precisely thinning of glass is introduced in this paper.By machining cavity on the surface of glass with a certain depth,the donor film can be coated in the glass cavity by doctor-blading.By this way,the thickness of the donor film can be precisely controlled.In this paper,precisely thinning of glass and laser induced forward transfer technology are combined together to fabricate the humidity microsensor.The main research contents of this paper are as follows:1.A picosecond laser was used to create cavities on the surface of soda-lime glass.The influences of laser pulse energy,laser pulse frequency and scanning speed on the preparation of glass grooves were investigated firstly.The laser pulse energy of 16.5μJ,pulse frequency of 30 k Hz and scanning speed of 30 mm/s were selected after investigation.By adjusting the scanning interval,the glass cavities with different depth from 5μm to 36.5μm can be achieved quickly.2.Laser induced forward transfer technology was used to fabricate silver lines.The influences of laser pulse energy,donor film thickness and the receiving gap on the preparation of silver points were investigated firstly.And the dynamic process of silver paste transfer process was captured by a high-speed camera for further analysis.The influences of laser pulse energy and scanning speed on the preparation of silver lines were further investigated.With the laser pulse energy of 14.7μJ,pulse frequency of 1 k Hz,donor film thickness of 24μm and the scanning speed of 20 mm/s,the continuous and stable silver lines with a width of92μm and a height of 2.1μm were obtained.Finally,heat treatment was applied to process the silver lines.The minimum resistivity of the silver lines obtained by heat treatment was6.2×10^-7Ωm.3.Laser induced forward transfer technology was used to fabricate graphene oxide film.The influences of laser pulse energy,donor film thickness and the receiving gap on the preparation of graphene oxide points were investigated firstly.And the dynamic process of graphene oxide transfer process was captured by a high-speed camera for further analyze.With the laser pulse energy of 8.7μJ,pulse frequency of 1 k Hz,the donor thickness of 18μm and the scanning speed of 20 mm/s,the continuous and stable graphene oxide lines with a width of 214μm were obtained.Finally,a large area of graphene oxide film was created by overlapping the continuous graphene oxide lines.4.The silver electrode was fabricated by laser induced forward transfer technology.Then the graphene oxide film was accurately transferred to the silver electrode,thus the humidity microsensor based on graphene oxide was prepared.The graphene oxide film was characterized by scanning electron microscope,atomic force microscope and Raman detector.Finally,the sensitivity and stability of the humidity microsensor were detected and analyzed.It can be seen that the microsensor showed rapid and stable response performance,good hysteresis and long-term stability.