Chapter 2: Needs and capabilities in low-force technology
This chapter reviews the measurement of small forces in the micro- to nano-newton range that is becoming a very important field of research within in micro- and nanotechnology, nanoindenters, AFM, micro-CMMs and so on. The generation and measurement of small forces have many applications in the various fields of technology. This chapter specifically presents force sensing methods and the capability for small force metrology in the NMIs and other institutions.
Chapter 3: Linear Elastic Model for triskelion suspension
This chapter starts with a brief overview of some fundamental elastic beam theory. Follow- ing this, a novel contribution of this chapter is the development of an enhanced linear elastic model for triskelion suspension in order to predict the stiffness of triskelion force artefacts. Unlike published examples, it has capability to set independently all potential significant design parameters, such as elbow angles and can allow any number and distribution of n suspension beams around the centre of the hub of force artefacts. The new linear elastic model for triskelion force artefacts will be used to investigate changes in the elbow angles of the triskelion force artefacts, the stabilities and stiffness of platform centre (hub).
Chapter 4:- Implementation of linear elastic model; Numerical experiments and data analysis
This chapter presents the development of the triskelion software program to implement the enhanced linear model. However, the computed results of the triskelion software program could be compared to some published data from another study (indirect validation) before proceeding to simulate results from geometries of trial designs. It specifically explores the variation in the angle at the elbow of the suspension beams. It is clear that artefacts of
these types must become non-linear with increasing deflection, so the validity of the simple model under different parameters needs full investigation.
Chapter 5:- Triskelion polymeric force artefacts; Specification and design
This chapter describes the use of polymeric triskelion force artefacts for the first time. The use of polymeric force artefacts has the commercial capability to exploit polymers in a mass production scale for triskelion force artefacts and the possibility to offer a low-cost approach that is highly useful for industries. The low-cost approach could bring a revolution in the use of polymers in the design of triskelion force artefacts, just like precision injection moulding in the commercial market.
Chapter 6:- Experimental analysis of stiffness; Classic triskelion force artefacts
This chapter covers the specification, design and use of the best bespoke method for testing the stiffness of triskelion force artefacts. The validation testing results of classical triskelion force artefacts were carried out using the triskelion software program. The results of classic triskelion force artefacts force artefacts were also presented in this chapter. A non-linearity is deducted from whole range of experiments of classic triskelion force artefacts and angle- beam triskelion force artefacts that follows a best cubic fit. This allows analysis for the range of validity of the enhanced linear elastic model for triskelion force artefacts. The concept of non-linearity was detected for the first time from the experimental result of classic and angle-beam triskelion force artefacts and was not seen in any scientific published research papers.
Chapter 7:- Experimental analysis of stiffness; Angle-beam triskelion force arte- facts
This chapter presents specification, design and fabrication using a low-cost approach for measurements of planar angle-beam suspensions that are introduced for the first time for force artefacts. Experimental results of angle-beam are compared with validated results of the triskelion software program. Like classic triskelion force artefacts, non-linearity was also detected for the angle-beam force artefacts that also follows best cubic fit and allows better range of performance as compared to the classic force artefacts.
Chapter 8:- Tetraskelion force artefacts; specification, design, experimental analysis of stiffness and numerical investigations
This chapter describes the extended research work for the design of tetraskelion force arte- facts. Two type of polymeric tetraskelion force artefacts (four legs) for classic and angle- beam tetraskelion force artefacts were fabricated. It was observed in the experimental research work that all the tetraskelion force artefacts belong to the triskelion force artefacts family and become significantly stiffer because they were kinematically constrained. This new idea is slightly counter-intuitive, being a trade-off between individual stiffness and a number of additional support legs which leads to better practical performance compared to three legs. The new polymeric tetraskelion force artefacts models and experimental tech- nique was developed and used for the preliminary investigation of these points. The poly- meric tetraskelion force artefacts were developed for the first time for practical testing and have never been published in any scientific research papers. Moreover, a new tetraskelion software program was developed by upgrading the triskelion software program to predict the stiffness of tetraskelion force artefacts before their fabrication and validation.
Chapter 9:- Best choices of triskelion and tetraskelion force artefacts for indus- trial applications
This chapter discusses the potential use of triskelion and tetraskelion force artefacts for commercial use. Their performance and working ranges in the linear region of the graphs plotted from the experimental data are described. The numerical experiments are also extended to explore the best variant design of triskelion and tetraskelion force artefacts or micro probe suspensions.
Chapter 10:- Conclusion and future recommendations
This chapter presents the conclusions for future research drawn from the research work presented in this thesis. The importance of a low-cost approach for commercial production and the best variant design for triskelion and tetraskelion micro probe suspension or force artefacts are also highlighted in this chapter.
Chapter 2
Needs and capabilities in low-force
metrology
2.1
Introduction
This chapter highlight the essential standard capabilities for low force metrology developed in various NMIs in the world. The current challenges are the base units (kg, m, s) of SI systems. The NMIs are motivated by the needs for small force standards and have started to explore new methods and techniques of calibration for SI-traceable force. The primary standards of force are derived from the unit of the Newton using base units of SI systems.
The realisation of an SI unit, ‘newton’ (or a fraction of it) in terms of base unit will involve complex and delicate instrumentation (often called a ‘secondary standards’). Such systems are impractical for almost any direct calibration, necessitating the development of intermediate (interfacing) devices: force transfer artefacts. Hence, the exploration of various methods and modelling techniques are carried out in this chapter for new design of “force transfer artefacts”. This is the starting point for the development of the research work presented in this thesis.
Furthermore, this chapter discusses force-sensing methods, which could be used for low force technology in the future.