Atomic Force Microscopy and Related Techniques Lab

From our main areas of interest, we have compiled six different master thesis proposals in which you can enroll either from a Physics or a Physics Engineering background. These proposals can be fine-tuned to the student's interest/background, so don't hesitate to email us if you want to lear more about any of these proposals.

Projects for Physics students

Non-contact viscoelasticity measurements of soft materials

Mechanical properties of materials such as elasticity or viscosity, have long been the focus of intensive research towards the development of novel materials and applications. Recently these properties have also been associated with critical aspects of cell life in the human body, from cell division to the formation of metastasis and death and are regarded as potential therapeutic targets for diagnosis of several diseases. However, the measurement and study of these properties is currently hindered by experimental challenges. Not only the traditional physical models underlying such experiments are often inaccurate, but also effects such as adhesion originate severe disturbances to the expected linear elasticity theories. In the AFMaRT Lab we are developing an innovative non-contact experimental method to probe the viscoelasticity of soft materials. In short, to avoid the detrimental effects of adhesion, we sense how soft and how viscous a material is without ever touching it, by oscillating nearby a colloidal probe, in a low Reynolds number regime. This project is centered in the development of this experimental method. After first contacting with the current challenges in measuring viscoelasticity with atomic force microscopes, and depending on the student’s interest, the proposed work plan, which includes learning how to use this instrument proficiently, can focus on the accurate modelling of the experimental setup and prediction of experimental results, and/or on the use of our lab AFMs to test and develop the proposed methodology on a large range of different test samples, from polymeric gel matrices to human lung cells.

Investigating liquids at the ultimate scale

If one wants to describe the nanoscale with only a few words, one of those must be ’wet’. In fact whenever water vapor is confined below a critical dimension, in all sorts of cavities, cracks or nanofissures, a water capillary bridge spontaneously condenses. This ubiquitous phenomenon directly influences a myriad of systems, from sandcastles to insect attachment, and offers significant challenges to the development of micro/nano electromechanical devices, which must coexist with these bridges. Due to the strong forces originated by the formation of such capillaries they also severely difficult any attempts to study this phenomenon. For instance, while capillary interactions and nucleation have been studied for centuries, only the formation time of capillary bridges, a key measurement to evaluate their nucleation dynamics, has been determined. Other fundamental questions, such as their critical nucleation distance, have not yet been clearly understood. We propose to study the still many unknowns about capillary bridges, to eventually develop a better understanding on the thermodynamics of this phenomenon. Considering the student’s interest, the idea is to use analytical reasoning, numerical modelling, and experimental tools in an attempt to answer significant questions in this area: given the small physical dimensions involved, can we still use classical thermodynamics? Why do current theories and experimental results disagree? The successful answer to these and other questions will pave the way for a new perspective into this still puzzling phenomenon.

Investigating nanofriction with harmonic oscillators

The control and measurement of friction is a target of research towards the development of novel materials and applications, but our understanding of the origins of friction, or on which physical factors does the friction coefficient depends on, is still poor. Recently we have studied the effect of sliding friction on common harmonic oscillators and developed a novel methodology to study and measure friction via the use of harmonic oscillators. This project follows from these recent developments and aims at expanding our theoretical and experimental knowledge about the subject. It will focus on further developing our experimental methodologies by using common watch quartz crystal oscillators (tuning forks), which are extremely cheap but very sensible devices. We plan to combine these experimental approaches with theoretical modelling of nanofriction, in an attempt to characterize nanofriction in different relevant tribological systems, under different thermodynamic conditions. The objective is to establish a quantitative relationship between the nanofriction at the liquid-solid interfaces and interfacial wetting.

Projects for Physics Engineering students

Development of a low-cost, high-resolution position sensor

High precision position sensors are increasingly used for automatizing control in multiple settings. One particular use is in atomic force microscopes. To improve their reliability and accuracy, these microscopes require a three-axial detection of the sample stage motion, with at least angstrom-level resolution. These, however, increase significantly the cost and footprint of AFMs. In the AFMaRT Laboratory we have been dedicated to developing low-cost AFMs which can match, or even surpass, the performance of commercial instruments. This master project thus follows this years-long investigation. After a first contact with the basics of atomic force microscopy, the student will design a position sensor that can be retrofitted to our microscopes, using low-cost strategies and taking advantage of our experience with AFM instrumentation. The student will take care of all the necessary steps to achieve optimal performance of the device, from hardware design or electrical processing to signal acquisition and calibration. The project will end with an assessment on the potential for dissemination of the developed technology.

Development, optimization and test of algorithms for atomic force microscopy experiments

The operation of atomic force microscopes requires the synchronous input, processing, and output of various signals which are vital for instrument performance. This is usually achieved through proprietary software accounting for a big share of the total cost of the instrument. However, in general, significant time and resources must be spent on developing specific data treatment software, in order to get the needed scientific insights. In the AFMaRT Lab we are dedicated to developing low-cost AFMs which match the performance of commercial instruments. A key part of this endeavour is the development of open, customizable software for AFM operation, the focus of this master project. After taking contact with the basics of AFMs, the student will address, according to his/her interests, three areas critical for the operation of AFMs: 1 – upgrade of our current software and data acquisition hardware, improving versatility and speed; 2 – development of devices for automatic pre-processing of the instrument signals; 3 – development of software routines to expedite data treatment, specifically for mechanical measurements and molecular unbinding experiments. All developments will be tested in our custom-made AFMs.

A metrologic approach to measuring mechanical properties of soft materials

Mechanical properties of materials such as viscoelasticity, have long been the focus of research towards developing novel materials and applications. In the last decades, atomic force microscopes enabled the association of these properties with critical aspects of life, from cell division to the formation of metastasis, establishing them as potential therapeutic targets for disease diagnosis. AFM measurements suffer, however, from multiple instrumental difficulties. Some measurement methodologies have been proposed to overcome them, but none of them gathers a clear consensus. This master project is focused on a key question: what is the best approach for measuring viscoelasticity in soft materials with AFMs? To solve it, the student will first become proficient with AFMs, learning and experiencing the different measurement methods proposed by the AFM community. Then, he/she will proceed with a metrologic comparison of selected measurement modes. This will include an initial modelling of experiments and the evaluation of each mode performance when studying, first, calibrated/referenced samples and, second, research-level test subjects, including biologic and non-biologic material.