9461179 Bryant This Small Business Innovation Research Phase I will investigate using microencapsulated phase change materials (microPCMs) in a fabric layer as a thermal barrier to extend the endurance and productivity of underwater divers in cold water. MicroPCM-enhanced fabrics could be used alone (passively) or in conjunction with an auxiliary heating device (actively). For Phase I research purposed, the research emphasis will be on studying the effectiveness of a microPCM fabric as a thermal barrier in a diver's dry suit. However the concepts developed here will also apply to wet suits. Phase I objectives will be to: select, encapsulate and evaluate thermal properties of appropriate PCMS; acquire coated microPCM fabric samples and controls and evaluate their thermal properties; design laboratory tests to evaluate thermal performance of test fabrics; and evaluate thermal performance of test fabrics with and without auxiliary heating. The potential use of microPCM material to keep diver's comfortable and extend their work period will be thoroughly examined and recommendations made to the NSF for a follow-on Phase II effort.