3D printing of DNA – Transmission Electron Microscopy
Researchers have developed a graphene liquid cell that can be used together with the conventional transmission electron microscopy (TEM) to view ‘soft materials’ in three-dimensional. The term ‘soft materials’ refers to a number of things, including biological compounds such as protein, plastics, DNA, flexible electronics, therapeutic drugs, and some types of photovoltaics.
Even though these materials form an integral part in our lives, it has been a challenge to study them conveniently. These materials (especially biological compounds) pose numerous questions, especially the way they behave at the nanoscale.
Through a combination of transmission electron microscopy (TEM) and their own unique graphene liquid cell, the researchers have recorded the three-dimensional motion of DNA connected to gold nanocrystals. This is the first time TEM has been used for 3D dynamic imaging of so-called soft materials. Conventionally, TEM focuses a beam of electrons on the soft materials to illuminate and magnify them as means of providing a resolution used to study their properties. This technique, unlike the use of light, requires a high vacuum setting since molecules in the air perturb the electron beam. In such a high vacuum environment, liquids evaporate. This necessitates soft materials that are highly viscous to be sealed hermetically using special solid containers. These containers, called cells, have a viewing window through which the TEM forms an image.
For some time now, these viewing windows have been made of silicon which limits the resolution of the soft materials under study because of its thickness. It also disturbs the soft materials’ natural state. To overcome these challenges, researchers have now developed a liquid cell made from graphene membrane, which is one atom thick.
They bonded two opposing graphene sheets to form a sealed nanoscale chamber. This chamber has within it a stable aqueous solution which is transparent to the electron beams of the TEM. This minimizes the loss of imaging electrons as well as provides a very high resolution which is touted to be very useful in studying soft materials.