Introduction There has been considerable interest in developing techniques to create three-dimensional micro-solenoids for microfluidic devices for use with magnetic materials. Although micro-solenoids have been developed for miniaturization of inductors for on-chip power supplies and dc-dc voltage converters [1] there has been limited use in microfluidic devices [2]. Although photolithographically defined two-dimensional, planar micro solenoids have been developed, when a 3D geometry coils is required they are limited to larger scales in the millimeter range or the micro solenoids are not hollow and are filled with material, thus cannot be used with a microfluidic channel [3]. In our work we have developed a fabrication process for a 75-micron radius, vacuum micro solenoid embedded in PDMS channel for microfluidics applications [4].The applications for micro-solenoids in Bio-Micro-Fluidic systems which range from cell sorting and filtering, to the detection and analysis of individual cells. We have also demonstrated when particles in fluid pass through the coil they can be easily detected from the inducted current in the coil [4]. This approach requires much less power than a flow cytometry laboratory instrument, which requires a laser source to detect the cells and particles. Method and Results The construction of the prototype solenoid is as follows: A piece of optical fiber is held taught, and a coil of 20-30 turns of 46ga enameled wire is wound around it. A small, hollow cylindrical magnet is threaded around the coil and fiber, and the arrangement is placed in a 3d printed mold. Syringe needles are threaded onto the fiber and inserted into holes in the mold. Polydimethylsiloxane potting compound is mixed and poured into the mold. The mold and PDMS is placed in a vacuum chamber for 30 minutes to de-gas. The PDMS is cured on a hot plate on low for about 4 hours. The needles are removed and the fiber is pulled out of the PDMS using pliers wrapped in tape. Discussion and Conclusions The image in figure 1 shows a completed micro-solenoid and the induced current readings from beads injected into the channel. The motivation for developing micro-solenoid for sensing is to increase the sensitivity, by match the diameter of micro-coil to the size of the biological cell sorting, so that individual cells can be counted using a magnetic labels attached to the cells. Such micro-solenoids can be used for the detection of labelled cells with magnetic beads attached in an immunoassay. They can be used for counting magnetic particles, or measuring the size of magnetization intensity of particles, based upon the induced current in the micro-coil. Ultimately, the method could be developed for detection of individual pathogenic bacteria or even viruses in a biological sample.