2.5 Conclusions

Since the discovery of the optical tweezers, the accuracy of the instrumentation and the number of applications have multiplied. The research in molecular biophysics has gone hand in hand with the development of optical tweezers during the last 20 years. What is more, optical tweezers have become a standard tool for the biophysicists. The future will bring us the combination of optical tweezers with other techniques, the parallelization of experiments and the refinement of manipulation.

The optical trapping of particles can be described from different complementary theories. None of them is quantitatively accurate, but they provide satisfactory approaches to the problem. The minitweezers is an instrument designed to produce optical traps and measure the force using the conservation of light momentum. This is a stable instrument that has high resolution and accuracy thanks to its size and compactness.

The acquisition of data and the control of the instrument is performed with customized electronic boards based on PIC microcontrollers. The advantage of using PICs is that the feedback algorithms such as constant force can be implemented at high bandwidth compared to other optical tweezers instruments.

Besides, the user interface was designed for a Mac computer, which is intuitive and easy to use. The instrument was conceived to be used by several experimentalists working on different topics. So the calibration only needs to be done once to make the instrument available to all users. The host application also allows to design and implement new protocols easily.

The research described in the next chapters of this PhD thesis was based on the experiments performed with the minitweezers instrument. Understanding the working of the instrument has been a key stone to set up the experiments and analyze the data.

The information contained in this chapter and its appendixes is part of the know-how of the Small Biosystems Lab. It has been included in this thesis in order to make it available to everyone as a useful reference for future studies.

JM Huguet 2014-02-12