Finding a suitable nanoscale motor capable of autonomous, unidirectional, linear motion is considered important to the development of DNA nanotechnology. The walkers have been shown to be capable of autonomous motion over linear, 2-dimensional and 3-dimensional DNA tracks through a large number of schemes.  In July 2005, Bath et al. showed that another way to control DNA walker motion is to use restriction enzymes to strategically cleave the track, causing the forward motion of the walkers. In 2010, two different sets of researchers exhibited the walkers more complex abilities to selectively pick up and drop off molecular cargo and to perform DNA-templated synthesis as the walker moves along the track. In late 2015, Yehl et al. showed that three orders of magnitude higher than the speeds of motion seen previously were possible when using DNA-coated spherical particles that would "roll" on a surface modified with RNA complementary to the nanoparticles DNA. RNase H was used to hydrolyse the RNA, releasing the bound DNA and allowing the DNA to hybridize to RNA further downstream. In 2018, Valero et al. described a DNA walker based on two interlocked, catenated circular double-stranded DNAs (dsDNAs) and an engineered T7 RNA polymerase (T7RNAP) firmly attached to one of the DNA circles. This stator-ring unidirectionally rotated the interlocked rotor-ring by rolling circle transcription (RCT), driven by nucleotide triphosphate (NTP) hydrolysis, thereby constituting a catenated DNA wheel motor. The wheel motor produces long, repetitive RNA transcripts that remain attached to the DNA-catenane and are used to guide its directional walking along predefined ssDNA tracks arranged on a DNA nanotube.