Force controlled atomic force microscopy for biological specimen.

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Feasibility of polyimide cantilever for force feedback method is studied. The stability of the force feedback system is mainly improved by small Q factor and the low resonant frequency of the cantilever. The polyimide cantilever is fabricated and investigated its mechanical feature, especially Q factor in a vacuum. Form these values the required bandwidth of the force feedback system is estimated. The polyimide cantilever reduces the frequency requirement to 1/20, compared with the SiN cantilever with same feature except for internal damping. The system stability is confirmed by numerical simulations. The bandwidth shortage results in large oscillation of the force curve. To increase biological compatibility of Ti-6Al-4V, thin film of hydroxyapatite (HAp) was deposited on the polished substrate(0.1〜3.0μmR_<max>) by ArF excimer laser in an atmosphere of O_2+H_2O.The gas pressure was kept at 13.3Pa (1×10^<-1>Torr) during the deposition. The substrate temperature was varied torn 500℃ to 5 … More 60℃. Crystal stractures of HAp film were evaluated by X-ray diffraction (XRD). At temperatures less than 500℃ the films resulted in amorphous. At temperatures greater than 560℃ the films had mixture phase of crystallized HAp and tricalcium phosphate (TCP). Surface morphology of HAp film was observed by atomic-force microscope (AFM). Mechanical properties of film were measured by the scratch test and the peeling off test by using tensile test machine. The following results were obtained : (1) The crystallized HAp was obtained at about 530℃, (2) In the scratch test, HAp film was clearly removed at the load of 18N, (3) In the peeling off test, the adhesive strength of HAp film on the substratewere about 2.3, 5.4 and 10MPa for the surface roughness 0.1, 1.0 and 3.0μmRmax, respectively and (4) Biocompatibility of HAp film was evaluated by in-vitro. Unfortunately, to investigate biological specimen the stability of the force control atomic force microscopy system is not sufficient. Farther improvement of the force control system is required. Less