An Integrated Compact Unit for Wide Range Micro-Newton Force Measurement

Abstract

Wide range compact sensor is preferably sought for force sensing in testing of micro objects or local area of macro objects with the observation of high resolution microscope. This paper presents the design and development of an integrated passive cantilever type force sensing unit with the specificities of range variation, interchangeability of components and compact size by incorporating with cantilever, probe and a capacitive sensor for measurement of large range micro-newton forces in wide scope of application. In the design, the tactile force at the probe perpendicularly attached to the cantilever is converted as cantilever deflection, which is measured by the capacitive sensor. In connection to a tiny capacitive sensor a compatible cantilever with double-beam structure is considered. Cantilever length variation facility is incorporated in the unit for obtaining different force measurement ranges by using the same cantilever. Characterization of the cantilever is performed against a standard load cell. The force resolution with a typical cantilever is estimated as 10 nN. The elastic property of human hair is efficiently determined by testing with the combination of a digital microscope and the developed sensor system. The utility of the unit for different resolution/range by the interchangeability of cantilevers is also demonstrated. Experimental results show that this integrated force sensing unit achieves good sensitivity and linearity, and wide measurement range.

A microscope system for characterization of mechanical properties of small-scaled objects

“…It was experimentally confirmed that the measurement uncertainty level of this type of force sensor was found within 0.4% of maximum load. The resolution of the present force sensor was about 10 nN [4].…”

“…1(b). This compact, integrated force sensor has variable force range and can be used for obtaining force responses from various types of smallscaled objects [4]. The cross sectional area of the cantilever beam was 0.54 × 0.05 mm and the beam length was 29.5 mm.…”

“…The microscope system, which was composted of a high-resolution digital microscope, a force sensor [4], a piezo stage, personal computer, etc., was used to record simultaneously the force response and the corresponding deformation pattern of the small-scaled objects during mechanical testing. To overcome the difficulty in handling the small-scaled objects and to facilitate a suitable experimental setup for testing, Joule heat welding technology [5] was adapted.…”

Mechanical Properties of Thin Al Wires Prepared by Electromigration

“…Details of the testing apparatus are described elsewhere. 22) Table I. 23) Those values in Table I are the average values of the examined three Al wires.…”

Accurate determination of the structural elasticity of human hair by a small-scale bending test

“…The maximum load for the force sensor was 670 mN, and it was experimentally confirmed that the measurement uncertainty of the sensor was less than 0.04% at the maximum load (o0.3 mN). Details of the force sensor are available in a previous paper (Akanda et al, 2010). The load-displacement curve was recorded for different loading directions (along the short or long axis in the elliptical crosssection of the hair) and at different loading positions (located 2 or 2.5 mm from the fixed end).…”