Engineered Functional Surfaces by Laser Microprocessing for Biomedical Applications

Metallic biomaterials are increasingly being used in various medical applications due to their high strength,fracture resistance,good electrical conductivity,and biocompatibility.However,their practical applications have been largely limited due to poor surface performance.Laser microprocessing is an advanced method of enhancing the surface-related properties of biomaterials.This work demonstrates the capability of laser microprocessing for biomedical metallic materials including magnesium and titanium alloys,with potential applications in cell adhesion and liquid biopsy.We investigate laser-material interaction,microstructural evolution,and surface performance,and analyze cell behavior and the surface-enhanced Raman scattering(SERS)effect.Furthermore,we explore a theoretical study on the laser microprocessing of metallic alloys that shows interesting results with potential applications.The results show that cells exhibit good adhesion behavior at the surface of the laser-treated surface,with a preferential direction based on the textured structure.A significant SERS enhancement of 6×10^3 can be obtained at the laser-textured surface during Raman measurement.

KEY TECHNOLOGY FOR PRACTICAL 1-mm-DIAMETER ELECTROMAGNETIC MICROMOTOR

A 1 mm diameter electromagnetic micromotor was developed as a crux component for MEMS application. The motor has a novel layer structure with a 1 mm diameter rotor in the middle of two stators with the same size. The stator uses multiple layers, slotless and concentrated planar winding. The rotor adopts multipolar permanent magnet with high performance. Ruby bearing is used to prolong operating lifetime of the micromotor. The stator winding, consisting of 6 layer coils, 42 turns, and 9 pairs, is fabricated with microprocessing techniques. The micromotor has long operation lifetime, its running speed is stable and controllable, and rotational direction can be easily reversed. Maximum achieved rotational speed of 18000 r/min with maximum output torque of 1.5 μ N·m has been obtained. This paper presented the key technology for developing this kind of micromotor including the design of structure, magnetic circuit, heat problem, friction improvement, microprocessing techniques, and so on.

Size effects on process performance and product quality in progressive microforming of shafted gears revealed by experiment and numerical modeling

As one of the indispensable actuating components in micro-systems,the shafted microgear is in great production demand.Microforming is a manufacturing process to produce microgears to meet the needs.Due to the small geometrical size,there are uncertain process performance and product quality issues in this production process.In this study,the shafted microgears were fabricated in two different scaling factors with four grain sizes using a progressively extrusion-blanking method.To explore the unknown of the process,grain-based modeling was proposed and employed to simulate the entire forming process.The results show that when the grains are large,the anisotropy of single grains has an obvious size effect on the forming behavior and process performance;and the produced geometries and surface quality are worsened;and the deformation load is decreased.Five deformation zones were identified in the microstructures with different hardness and distributions of stress and strain.The simulation by using the proposed model successfully predicted the formation of zones and revealed the inhomogeneous deformation in the forming process.The undesirable geometries of microgears including material unfilling,burr and inclination were observed on the shaft and teeth of gear,and the inclination size is increased obviously with grain size.To avoid the formation of inclination and material unfilling,the punch was redesigned,and a die insert was added to constraint the bottom surface of the gear teeth.The new products had then the better forming quality.