Stochastic thermodynamics [1,2] is a recently developed framework to deal with the thermodynamics at the microscope, where thermal fluctuations strongly influence their behaviour. Typical such systems are colloids and biomolecules or cells. These thermal fluctuations do not only lead to Brownian motion, but to a continuous and unavoidable heat exchange between the suspending medium and the particles, leading to a very interesting phenomenology. In order to explore such phenomenology and to test theoretical results obtained from stochastic thermodynamics, we developed an “experimental simulator” of thermodynamic devices in the microscale with an optically trapped bead that is subject to an external noise that mimics a controllable thermal bath. The noise is applied by means of electric fields acting on the charge of the trapped particle.
In this talk, I will present some of the results we obtained with this simulator, demonstrating excellent control over the effective temperature of the system and a control parameter. This allows us to perform a variety of equilibrium and non-equilibrium thermodynamic processes [3-5]. In particular, we were able to realize microadiabatic processes, where no heat is exchanged on average between the particle and the medium . This achievement allowed us to implement a Carnot microengine as a concatenation of isothermal and adiabatic processes , whose theoretical study is playing a key role in the foundations of stochastic thermodynamics.
 K Sekimoto; Lecture Notes in Physics (Springer, Berlin, 2010), Vol. 799.
 U Seifert; Rep. Prog. Phys. 75 (2012) 126001
 IA Martínez, E Roldan, JMR Parrondo, D Petrov; Phys. Rev. E 87 (2013) 032159
 É Roldán, IA Martínez, L Dinis, RA Rica; Appl. Phys. Lett. 104 (2014) 234103
 P Mestres, IA Martinez, A Ortiz-Ambriz, RA Rica, E Roldan; Phys. Rev. E 90 (2014) 032116
 IA Martínez, E Roldan, L Dinis, D Petrov, RA Rica; Phys. Rev. Lett. (2015) In press
 IA Martinez, E Roldan, L Dinis, D Petrov, JMR Parrondo, RA Rica; (2015) arXiv preprint: 1412.1282
We studied fluctuations of an optically trapped bead connected to a single DNA molecule anchored between the
bead and a cover glass or between two optically trapped beads. Power spectral densities of the bead position for
different extensions of the molecule were compared with the power spectral density of the position fluctuations of
the same bead without the molecule attached. Experiments showed that the fluctuations of the DNA molecule
extended up to 80% by a force of 3 pN include the colored noise contribution with spectral dependence 1/fα
with α~ 0.75.