Force Measurement Capabilities Research Articles

Experimental Characterization of Micro-Friction on a Mica Surface Using the Lateral Motion and Force Measurement Capability of an Instrumented Indenter

An experimental characterization of friction forces between asymmetric surfaces in the micro-regime is presented. The lateral motion and force-measurement capability of an instrumented indenter (triboindenter) is characterized and explored for determining friction properties at low velocities. Friction experiments are performed using the triboindenter with high repeatability. It is observed that real-time depth measurements closely follow the Hertzian prediction. Friction spikes with magnitudes depending on the drive velocity input are observed with peak friction force increasing with the dwell time. Anisotropy is observed between surfaces of different materials with stick-slip occurring only at specific relative orientations. Directions for expanding the current range of the triboindenter to obtain data from the nano to the macro scale are also presented.

On‐site three dimensional force sensing capability in a laparoscopic grasper

Advancements in robotics have led to significant improvements in robot‐assisted minimally invasive surgery. This paper describes our design of an automated laparoscopic grasper with tri‐directional force measurement capability at the grasping jaws. The laparoscopic tool can measure normal, lateral, and longitudinal grasping forces while grasping soft tissue. Additionally, the tool can also be used to measure the tissue probing forces. Initial testing of the prototype has shown its ability to accurately characterize artificial tissue samples of varying stiffness and accurately measure the probing forces.

Deformation mechanisms in free-standing nanoscale thin films: a quantitative in situ transmission electron microscope study.

We have added force and displacement measurement capabilities in the transmission electron microscope (TEM) for in situ quantitative tensile experimentation on nanoscale specimens. Employing the technique, we measured the stress-strain response of several nanoscale free-standing aluminum and gold films subjected to several loading and unloading cycles. We observed low elastic modulus, nonlinear elasticity, lack of work hardening, and macroscopically brittle nature in these metals when their average grain size is 50 nm or less. Direct in situ TEM observation of the absence of dislocations in these films even at high stresses points to a grain-boundary-based mechanism as a dominant contributing factor in nanoscale metal deformation. When grain size is larger, the same metals regain their macroscopic behavior. Addition of quantitative capability makes the TEM a versatile tool for new fundamental investigations on materials and structures at the nanoscale.

Micromechanical testing of MEMS materials

This paper discusses tensile testing techniques and results derived as part of a broader microstructure-properties investigation of structural materials used in surface micromachined (SMM), and LIGA MEMS technologies. SMM techniques produce devices on the surface of a silicon wafer, with critical dimensions as small as 1–2 μm, using a subtractive multilayer film deposition process. Two structural materials have been investigated: SUMMiT™ polysilicon and amorphous Diamond (a-D). Mechanical properties presented in this paper on these SMM structural materials were obtained from a direct tensile testing method using the lateral force measurement capability of a nanoindentation system. LIGA, a German acronym extracted from the words “Lithographie, Galvanoformung, Abformung,” is an additive process in which structural material is electrodeposited into a polymethyl-methacrylate (PMMA) molds realized by deep x-ray lithography. LIGA tensile specimens of several different materials have been evaluated using a mini-servohydraulic load frame, designed to test specimens of sizes similar to structural components. In this paper, tensile test results from LIGA fabricated Ni and Ni-alloys and examples of their correlation to processing and microstructure will be presented.

Atomic Force Microscopy with Patterned Cantilevers and Tip Arrays: Force Measurements with Chemical Arrays

Interactions between molecules and at interfaces are vital to many scientific and technological fields. Techniques such as atomic force microscopy (AFM) have been used to measure forces and force gradients associated with interactions between individual molecules as well as interactions between interfaces. A recent alteration of the AFM configuration combined a tipless cantilever with an array of substrate supported tips. Herein, we present a further extension of AFM force measurement capabilities, by chemically patterning both the cantilever and the tip array. In a proof-of-concept experiment a gold-coated cantilever and tip array were patterning with alkylthiolate monolayers, and the interfacial forces were measured for the various combinations. This patterning allows many different interactions to be rapidly measured in situ, under identical conditions, thereby improving reliability and opening the door to combinatorial applications. Future developments are discussed including the means to measure hund...

The surface apparatus--a tool for probing molecular protein interactions.

The measurements described demonstrate the variety of protein or protein-mediated interactions that can be probed directly with the SFA. The distance, force and dynamic measurement capabilities provide tremendous potential for the identification and quantification of the molecular mechanisms and forces that both determine protein properties and influence protein function in diverse environments.