We have developed a laser-based printing technique, called biological laser printing (BioLP). BioLP is a non-contact, orifice-free technique that rapidly deposits fL to nL scale volumes of biological material with spatial accuracy better than 5 microm. The printer's orifice-free nature allows for transfer of a wide range of biological material onto a variety of substrates. Control of transfer is performed via a computer-aided design/computer-aided manufacturing (CAD/CAM) system which allows for deposition rates up to 100 pixels of biological material per second using the current laser systems. In this article, we present a description of the apparatus, a model of the transfer process, and a comparison to other biological printing techniques. Further, examples of current system capabilities, such as adjacent deposition of multiple cell types, large-scale cell arrays, and preliminary experiments on creating multi-layer cell constructs are presented. These cell printing experiments not only demonstrate near 100% viability, they also are the first steps toward using BioLP to create heterogeneous 3-dimensional constructs for use in tissue engineering applications.

No abstract

A miniature microbial fuel cell (mini-MFC) is described that demonstrates high output power per device crosssection (2.0 cm 2 ) and volume (1.2 cm 3 ). Shewanella oneidensis DSP10 in growth medium with lactate and buffered ferricyanide solutions were used as the anolyte and catholyte, respectively. Maximum power densities of 24 and 10 mW/m 2 were measured using the true surface areas of reticulated vitreous carbon (RVC) and graphite felt (GF) electrodes without the addition of exogenous mediators in the anolyte. Current densities at maximum power were measured as 44 and 20 mA/m 2 for RVC and GF, while short circuit current densities reached 32 mA/m 2 for GF anodes and 100 mA/m 2 for RVC. When the power density for GF was calculated using the cross sectional area of the device or the volume of the anode chamber, we found values (3 W/m 2 , 500 W/m 3 ) similar to the maxima reported in the literature. The addition of electron mediators resulted in current and power increases of 30-100%. These power densities were surprisingly high considering a pure S. oneidensis culture was used. We found that the short diffusion lengths and high surface-area-to-chamber volume ratio utilized in the mini-MFC enhanced power density when compared to output from similar macroscopic MFCs.