Microfabrication processes and I-V characteristics are reported for a set of free-floating cubic microparticles with electrodes biased by one or two onboard photovoltaic cells. The anodes of such microparticles can serve as a site for the growth of metal reducing bacteria, and the ability of the microparticles to flow freely in aqueous solutions means that diffusion limitations on the nutrient supply for bacterial growth are partially overcome. One or two pn junctions are formed using electrically isolated mesas on the particles with a junction depth of 1 µm and a doping concentration of higher than 1020 cm-3. An AlSi (1%) metallization is used to avoid spiking during ohmic contact formation within the shallow n-type junctions. The photoresponse of the etch-released microparticles demonstrates an open circuit voltage of 0.4 V , appropriate for assisting electron transfer across an electrode-bacteria interface. The short circuit current density reaches 5-50 A/m2 under low light conditions (about 9.0 nW), which is greater than typical maximum microbial biofilm current densities.