We introduce a new Periodic micro coaxial transmission line (PMTL) that is capable of sustaining a TEM propagation mode up to THz band. The PMTL can be manufactured using current photolithographic processes. This transmission line can be embedded in microscopic layers that allow many new applications. We further use the embedded PMTL to develop a modular, scaleable and fully automated Universal Test Fixture for testing chips in various stages of development mainly for digital IC chips that can be utilized in production lines with pick and place of chips on tape to test every chip before insertion into circuits. The PMTL can also provide Confined Field Interconnects between various elements on semiconductor wafers to reduce parasitic and radiation losses and practically eliminating cross talk, thus, increasing the speed of digital IC's. The PMTL is also used to develop a Universal Test Socket, and a Hand Probe.