<unk> s are hypothetical, microscopic, artificial red blood cells that are intended to emulate the function of their organic counterparts, so as to supplement or replace the function of much of the human body's normal respiratory system.<unk> s were proposed by Robert A. Freitas Jr in his 1998 paper "A Mechanical Artificial Red Blood Cell: Exploratory Design in Medical Nanotechnology".<unk> s are an example of molecular nanotechnology, a field of technology still in the very earliest, purely hypothetical phase of development. Current technology is not sufficient to build a<unk>  due to considerations of power, atomic-scale manipulation, immune reaction or toxicity, computation and communication.
Respirocyte
Centrocyte
Corneocyte
Koilocyte
Dendritic cell
Podocyte
Prolymphocyte
Mast cell