Abstract: We have developed optical methods to indicate when micro-organisms are present in a single electrodynamically levitated microdroplet and to measure their motion within it. The approach was to develop a method for holding saturated salt water droplets in an approximate thermodynamic equilibrium in a quadrupole balance. We then captured droplets containing subparticles or guests approximating the size of typical micro-organisms. The presence and motion of these guests in the host droplet is indicated by both photon correlation spectroscopy and by fluctuations in the emission of fluorescence. Finally we show that the system may be used with real micro-organisms by capturing a microdroplet of the growth medium (minus nutrients) for the micro- organism, Halobacterium halobium with those micro-organisms contained in it. Halobacteria halobium were chosen for the model system because they thrive in a growth medium containing a nearly saturated solution of NaCl which we have found is particularly amenable to handling in our present apparatus. !14
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