An accelerator assembly includes a first chip and a second chip. An acceleration channel is formed into a surface of a first side of the first chip. The first side of the first chip is covalently bonded to a first side of the second chip such that the channel is a tubular void between the first and second chips. The channel has a tubular inside sidewall surface, substantially no portion of which is a metal surface. The channel has length-to-width ratio greater than five, and a channel width less than one micron. There are many substantially identical channels that extend in parallel between the first and second chips. In one specific example, the assembly is part of a Direct Write On Wafer (DWOW) printing system. The DWOW printing system is useful in semiconductor processing in that it can direct write an image onto a 300 mm diameter wafer in one minute.