Any active mechanical system uses an engine that converts chemical or electrical energy into mechanical work. In biological systems, such work is carried out by motor proteins. Despite the success of building rotary engines, designing and building artificial nanoscale counterparts of these complex biological motors has proven challenging.
Nanoscale Rotary Mechanisms
Of the critical steps in creating nanoscale rotary engines is demonstrating their ability to convert local free energy into designed mechanical motion. Previous experiments led to multiple designs of rotary assemblies and established a certain level of directed motion.
Molecular dynamics simulations have also shown the feasibility of using a DNA helix to convert electric fields into torque. However, scientists find it difficult to achieve experimental demonstration of a rotary mechanism that is programmed for sustained conversion of electric potential into mechanical rotation.
According to Professor Aleksei Aksimentiev of the University of Illinois, typical macroscopic machines get inefficient at the nanoscale. Experts must develop new principles and physical mechanisms to realize electromotors at tiny scales.
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Robotics at the Nanoscale
A team of researchers led by Hendrik Dietz of the Technical University of Munich and Cees Dekker of the Delft University of Technology has recently produced the first working nanoscale electromotor in history. It was made possible by designing a turbine engineered from DNA powered by hydrodynamic flow inside a nanopore. Their study is discussed in the paper "A DNA turbine powered by a transmembrane potential across a nanopore."
The small motor was created by manipulating DNA molecules. It contains a turbine of three blades with a total length of about 72 base pairs and 30 double-stranded DNA helices customized onto an axle.
All-atom molecular dynamics simulations were performed to characterize the physical events involved in operating the motor. Using a system of 5 million atoms, the researchers proved that the turbine could revolve when applied to an electric field.
Operating a DNA nanoturbine successfully draws on a prior study that utilized Frontera and ACCESS supercomputers. In this study, a single DNA helix has been the smallest electromotor possible, rotating at up to a billion revolutions per minute.
According to Aksimentiev, DNA has emerged as a nanoscale building material with many potential applications. DNA base pair is a powerful programming tool whose geometry and dimension can be programmed.
Another reason for using DNA as a building block is its negative charge, which is needed to create an electromotor. The researchers noted they wanted to reproduce ATP synthase as one of the most spectacular biological machines driven by electric fields. For their study, Aksimentiev and his colleagues built their motor with DNA.
The new material is also the first nanoscale motor, which allowed researchers to control the rotational speed and direction. This was accomplished by changing the electric field across the solid-state nanopore membrane and the salt concentrations in the fluids around the rotor.
The tiny motor developed by the team could be a catalyst for future research into applications such as building molecular factories to produce valuable chemicals. It also shows potential in medical probes that identify cancer and other diseases using molecules in the bloodstream.
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