Mechanical Resonators for Material Characterization: Sensor Development and Applications

Andrea Casci Ceccacci

Research output: Book/ReportPh.D. thesisResearch

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Abstract

The goals of this PhD project were to provide new approaches and developing new systems for material characterization, based on micro and nanomechanical sensors.
Common issues that have shown to hinder large-scale integration of sensing techniques based on a micromechanical sensor are the readout and sample handling. To address the first point, a semi-automatic characterization platform based on the optics and the mechanics of a commercial Blu-Ray pickup head unit was developed. Microbridges were chosen instead of microcantilevers to provide more robustness to the sensor. By embedding the sensor in a single-use microfluidic cartridge, the experimental condition was improved. The sample handling, as well as the environmental condition of the phenomena under test, are better controlled. As proof of concept to test the capabilities of the system, we studied the biopolymer degradation of Poly Lactic-co-Glycolic Acid (PLGA), which is of high relevance in the biomedical research field. A second version of the system is currently under development, and it aims to increase the throughput of the system allowing to read out multiple microbridge arrays.
For material characterization, spectroscopy analysis is often considered a benchmark technology. Conventional infrared spectroscopy approaches commonly require milligram amount of sample. Considering the frame of reference given by the overall aim of the project, mechanical sensors can be exploited to provide a unique tool for performing spectroscopy on a limited amount of sample. In this project, a nanomechanical photothermal sensor has been designed, developed and exploited to perform thin film Infrared Spectroscopy. Contrary to what has been previously shown, this work has focused on a membrane sensor providing a robust experimental approach which better suit sample quantification and preparation. The purpose of the studies presented here is to show the real potential of photothermal spectroscopy based on a nanomechanical sensor and to provide a method to maximise the signal to noise ratio (SNR) from a single acquisition. The methodology presented showed that it is possible obtaining a high SNR of 300 on a 20nm thick polymer layer showing a substantial improvement compared to the benchmark technique, attenuated total reflectance spectroscopy (ATR-FTIR).This high sensitivity allowed us to observe the chemical modification occurring during the gelification of a submicron thick layer of poly-vinyl-pyrrolidone (PVP) corresponding to picogram quantity of material.
Original languageEnglish
PublisherDTU Nanotech
Number of pages220
Publication statusPublished - 2017

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