Design Of Rotary Symmetrical Cantilever For High Precision Mechanically Scratching Fabrication

Micro-nano technology is widely used in biology,medicine,microelectronics,textile industry,military science,industrial manufacturing and other fields.High-precision devices at the micro-nano scale must be processed with specific equipment and advanced technical methods.Scanning probe lithography is a micro-nano processing method that does not rely on complex manufacturing processes and expensive equipment,and has an attractive prospect in the fabrication of low-cost,high-precision micro-nano structures.In the Scanning probe lithography,the components used to support and fix the probe are cantilever or cantileverlike structures.The cantilever is an important tool for sensitivity detection and signal feedback,which affects the quality of scanning probe lithography.Mechanical scribing is an important processing method in Scanning probe lithography.However,a single cantilever(one end is free and one end is fixed)is mainly used in the current mechanical scribing process.The structural characteristics of the single cantilever will cause the free end of the probe to be deflected when it contacts the surface of the sample,which in turn causes the probe to scribe a slip line on the sample substrate,causing the needle drop to slip.Rotational symmetry structure,the lateral stiffness of this structure is different in each direction,so that when the probe tip is subjected to a constant lateral force,the deflection angle in each direction is different,which is easy to cause the width and depth of scratches to vary.The above two situations jointly cause the machining error of the single cantilever,which brings a huge challenge to the realization of high-precision mechanical scribing technology.In view of the above problems,this paper firstly analyzes the working principle of a single cantilever and optimizes cantilevers with different structures by means of finite element analysis,and then designs a high-precision loading cantilever that can reduce the above machining errors.Finally,mechanical scribing experiments are used to verify its functionality.The main research contents of this paper are as follows:(1)Analysis of error generation process of single cantilever in mechanical scribingAnalyzing the causes of errors in the mechanical scribing process of a single cantilever has guiding significance for the design of a high-precision loading cantilever.The analysis results show that the single cantilever has two significant shortcomings in the mechanical scribing process: First,due to the geometrical characteristics of one end of the single cantilever fixed and the other free,the probe will deflect when in contact with the sample matrix,which will cause dropouts.Needle slip error;secondly,due to the different stiffness of the single cantilever in all directions during the mechanical scribing process,when the probe tip is subjected to a certain normal load and lateral force,the deflection in each direction is different.The error can be referred to as the error caused by different stiffness in each direction.This analysis provides an important basis for the design of high-precision loading cantilevers.(2)Design of high precision loading cantileverAccording to the requirements of high-precision mechanical scribing,several cantilever structures are designed and optimized.Firstly,according to the results of the error analysis of the single cantilever,four design bases for the high-precision loading cantilever are proposed,and the main force bearing structure of the high-precision loading cantilever—the folded beam of rotational symmetry is designed.Secondly,the type of rotationally symmetrical folded beam is selected according to the finite element analysis,and the structure optimization and strength check are carried out in turn.Then,after designing the highprecision loading cantilever—the rotationally symmetric cantilever,the fatigue checking and accuracy analysis are carried out.The results show that the rotationally symmetric cantilever meets the design requirements.Finally,the rotationally symmetric cantilever is fabricated,and the actual measurement of the normal elastic coefficient of the cantilever is carried out.The results show that the normal elastic coefficient can meet the design requirements.(3)Experimental research on mechanical scribing based on rotational symmetric cantileverTaking the machining results of a single cantilever as the control group,a series of mechanical scribe machining experiments were carried out using a rotationally symmetric cantilever,and the machining experiments of two kinds of cantilever indentations under different normal loads were studied.The results show that the indentation depth of single cantilever and rotationally symmetric cantilever increases with the increase of the normal load,while the single cantilever has a tail drag due to the slip of needle drop,and the dragging length increases with the increase of the load;the indentation profile of the rotationally symmetric cantilever is approximately a circle,indicating that the probe will not deflect when only the normal load is applied.Under the same normal load,the indentation depth of the rotationally symmetric cantilever is larger than that of the single cantilever.This paper further compares the machining capabilities of the rotationally symmetric cantilever and the single cantilever under different normal loads,machining speeds and reciprocating times.The experimental results show that the machining capability of the rotationally symmetric cantilever is better than that of the single cantilever.Finally,some complex two-dimensional patterns were processed by using the rotationally symmetric cantilever.The results show that the rotationally symmetric cantilever can greatly improve the machining quality of mechanical scribing.In conclusion,the designed rotationally symmetric cantilever with isotropic stiffness can reduce or even eliminate the needle drop slip error,and is also suitable for high-speed machining(≥ 5 mm/s),exhibiting excellent machining capability.In the mechanical scribing process,the indentation,anisotropic line scribing,machining speed and reciprocating machining experiments were carried out with the machining results of a single cantilever as a control.The results show that the rotationally symmetric cantilever is suitable for mechanical scribing.In more complex two-dimensional pattern processing,the rotationally symmetric cantilever can also show good processing effect,so it can be used for highprecision micro-nano scribing processing.The research content of this paper can provide reference for the design of other types of high-precision scribing cantilevers.