New Indentation Method

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Invention Summary:  Accurate indentation measurement is fundamental to atomic force microscope (AFM)-based material property characterization as the force applied and the indentation generated are the two most important physical variables that must be measured in the characterization process. Large measurement errors occur when the measurement frequency range becomes large (i.e., broadband), or the indentation is measured in liquid on soft materials. Such large measurement errors are generated due to the inability of the conventional method to account for the convolution of the AFM instrument dynamics with the viscoelastic response of the soft sample when the measurement frequency becomes large. Moreover, the conventional method of open-loop designs also fail to account for the random like thermal drift and the distributive hydrodynamic force effects when measuring the indentation in liquid, resulting in large measurement errors. Researchers at Rutgers have developed a control-based approach to address these challenges and the limits of the conventional approach. The invention is an accurate (MIIC) modeling-free inversion based iterative learning control method on AFM. When the cantilever tracks the same trajectory on different samples, the difference of cantilever base displacement is equivalent to the nano-indentation difference. The proposed method is not limited by the AFM z-axis dynamics, and this improvement is proved by both the theoretical analysis and the experimental results. Experimental results clearly show the efficacy of the proposed approach to the indentation measurement during broadband and in-liquid nano-mechanical measurements. The new control-based approach achieves accurate indentation quantification in broadband and in-liquid nanomechanical property measurements.  Market Application:  Indentation quantification in broadband and in-liquid nanomechanical property measurements  Advantages:  Achieves accurate indentation quantification in broadband and in-liquid nanomechanical property measurements Proposed method is not limited by the AFM z-axis dynamics Difference of cantilever base displacement is equivalent to the nano indentation difference. Intellectual Property & Development Status:  Patent pending