This paper describes a procedure for identifying mass and stiffness imperfections present in a microring gyroscope. In general mass and stiffness imperfections will be present as a result of fabrication variances and will contribute to mistuning of the gyroscope. Both mass and stiffness imperfections are treated as perturbations of the ideal isotropic mass and stiffness. The mass and stiffness perturbations are combined to form a structural imperfection, which is shown to be determinable from Nyquist plots of the frequency response functions. An analysis of electrostatic "tuning" is presented and demonstrates that the nonlinear negative spring component produced from a particular arrangement of capacitive electrodes is capable of removing such structural imperfections. If uncorrected the structural imperfections would otherwise result in anisoinertia and anisoelasticity. A comparison between the theoretically predicted tuning voltage and the experimentally derived value is made and shown to be in agreement. The major advantage of electrostatic tuning is that it may be implemented on-chip during operation thus providing active tuning. This is in contrast to the trimming techniques employing laser ablation or focussed ion beam, which may only be done prepackaging.

Graphene application within electrochemical sensing has been widely reported, but mainly as a composite, which adds summative effects to an underlying electrode. In this work we report the use of laser-scribed graphene as a distinct electrode patterned on a non-conducting flexible substrate. The laser-scribed graphene electrode compared favourably to established carbon macroelectrodes when evaluating both inner sphere and outer sphere redox probes, providing promise of extensive utility as an electrochemical sensor. The laser-scribed graphene electrode demonstrated the fastest heterogeneous electron transfer rate of all the electrodes evaluated with a k⁰ of 0.02373 cm s⁻¹ for potassium ferricyanide, which exceeds commercially available edge plane pyrolytic graphite at 0.00260 cm s⁻¹, basal plane pyrolytic graphite at 0.00033 cm s⁻¹ and the very slow and effectively irreversible electrochemistry observed using single layer graphene. Finally and most significantly, a proof of principle system was fabricated using the laser-scribed graphene as working electrode, counter electrode and underlying base for the Ag/AgCl reference electrode, all in situ on the same planar flexible substrate, removing the requirement of macroscale external electrodes. The planar three electrode format operated with the same optimal electrode characteristics. Furthermore, the fabrication is inexpensive, scalable and compatible with a disposable biosensor format, considerably widening the potential applications in electrochemical bio-sensing for laser-scribed graphene.

Until now, a difficult prospect in XPS imaging has been the identification of similar chemical states of carbon. With the advent of novel nano-carbons such as nanotubes and graphene, the ability to easily and unambiguously identify materials of varying sp2/sp3 nature in XPS spectra and images is becoming increasingly important. We present herein methods for the identification of such species in XPS images by shifting focus from the traditionally analysed C1s region to the X-ray induced carbon Auger feature. By extracting the D-Parameter from XPS data, we have generated what we refer to as “D-Parameter Images”, that clearly identify regions of different carbon hybridisation in an image of a graphite flake mounted on carbon tape, and areas of reduced graphene oxide (GO) in a laser-scribed GO film. This method is then enhanced by multivariate analysis, a technique we call “Multivariate Auger Feature Imaging”, where the distinction between varying sp2 carbon content on a surface is improved

Calibration of atomic force microscope (AFM) cantilevers is necessary for the measurement of nanonewton and piconewton forces, which are critical to analytical applications of AFM in the analysis of polymer surfaces, biological structures and organic molecules at nanoscale lateral resolution. We have developed a compact and easy-to-use reference artefact for this calibration, using a method that allows traceability to the SI (Système International). Traceability is crucial to ensure that force measurements by AFM are comparable to those made by optical tweezers and other methods. The new non-contact calibration method measures the spring constant of these artefacts, by a combination of electrical measurements and Doppler velocimetry. The device was fabricated by silicon surface micromachining. The device allows AFM cantilevers to be calibrated quite easily by the 'cantilever-on-reference' method, with our reference device having a spring constant uncertainty of around ± 5% at one standard deviation. A simple substitution of the analogue velocimeter used in this work with a digital model should reduce this uncertainty to around ± 2%. Both are significant improvements on current practice, and allow traceability to the SI for the first time at these nanonewton levels.