The Nano Channel Chip
for TEM applications
The Nano Channel Chip was specifically developed for use in TEM and works with any of our holders for flow, static and heating applications.
What makes the chip ideal for TEM is the precise control of liquid thickness which is made from 20 nm and all the way up to micrometers!
Also, the Silicon Nitride membranes are made down to 10 nm thin and do not bulge more than ~10 nm during a TEM session, due to the channels being so narrow, about 1-2 µm each.
This ensures that the advanced flow- and mixing experiments performed in TEM, are always at high resolution and batch-production of chips make the experiments reproducible.
Filling, flowing, and mixing in the Nano Channel Chip
Filling
The Nano Channel Chip is mounted in a TEM or SEM holder in less than five minutes. From here, the holder can be placed in the microscope, tubes can be attached to the backside of it and liquids can be flown into the system. The channels are filled almost instantaneously as liquid comes into contact with the highly hydrophilic channel surfaces. Capillary forces on the order of 10 bar ‘suck’ in the liquid forcefully, ensuring a complete filling.
Flowing
After the liquid has filled up the chip, the capillary forces are no longer acting on the liquid. From here, the pressure applied to the micro/bypass channels will determine the flow inside the channels: A larger pressure on one bypass channel will push the liquid through to the other bypass channel, and vice versa. It is impossible to see flow in the channels if there is nothing in them, moving. Therefore, to verify flow in the channels, we have often used nano particles which can be assumed to move precisely along with the liquid.
Mixing
The two bypasses in the holder can be used to fill the chip with two different liquids that can come together via nano channels in the field of view. We have developed four mixing methods that depend on diffusion and flow in the channels. One of the methods involves simply letting the two liquids merge into a central channel as seen in the image here.
The other mixing methods are described in more detail in our product brochure which you can download here:
But what about bubbles?
This is a question we get a lot and luckily the answer is good! Because bubbles are usually ‘squeezed’ out of the liquid and dissolve into it, exactly because of the large capillary pressure in the small nano channels. A video of the filling of channels, slowed down, can be seen on our LinkedIn page here. In this video, you can also see ‘dead-end’ channels being filled with water, trapping air/bubbles. However, within 10 seconds, most of these bubbles have disappeared.
Biological samples
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Insight Chips believes that it is necessary to supplement cryogenic data of biological samples like proteins and viruses with in-situ data of these particles in their native liquid state, at 37 C. For this, it is of utmost importance to control liquid- and membrane thickness as precisely as possible - and Insight Chips are currently the only ones in the world who can do this reliably. Therefore, we are currently developing methodology to get as far as we can in this field. So far, we have promising preliminary data with ferritin, VLPs and liposomes.Now, we are looking for partners that can help us fine-tune the methodology for 3D reconstruction and high resolution imaging for in-situ data while mixing new liquids with biological particles.
Glycine crystals
The Nano Channel Chip enables mixing in the field of view, inside the nano channels, which can be used to study protein crystals with well-defined thickness inside the TEM. So far, we have experience with growing Glycine crystals in the TEM and collecting 3D electron diffraction maps. The work shown here has been carried out in collaboration with Prof. Xiaodong Zou (SU) and Prof. Kristian Mølhave (DTU) with the help of Edward Broadhurst, Tayyaba Malik and Hongyi Xu.
MOFs
MOFs can be grown inside the Nano Channel Chip via mixing of two liquids directly in the field of view. We have had repeated luck with growing ZIF-8 inside the channels by mixing liquid solutions of Zinc Acetate and 2-methylimidazole. The results shown here are from a collaboration with prof. Kristian Mølhave and prof. Joe Patterson and the work has been carried out by PhD candidates Joakim Lajer (DTU) and Justin Mulvey (UCI).
Growth and dissolution
Nanoparticle growth and dissolution is one of the most ideal applications for the Nano Channel Chips, because Å-resolution is consistent and reliable for high-Z materials and sample preparation can be near-effortless - Just drop cast the solution into the chip, insert the chip in the holder, screw the lid on, and it’s ready for imaging. In collaboration with prof. Ute Kaiser’s group at Ulm University, we had some great success imaging Å-level resolution gold nucleation, shown in the video to the left.
3D electron diffraction
Our static TEM holders can tilt up to 45 degrees with 5.2 mm clearance between the pole piece gaps, allowing for collection of electron diffraction data from a range of angles.
In the video to the right is the 3DED map of a glycine crystal grown in our Nano Channel Chip was studied, revealing intriguing structural details via +/-15 degrees tilt in a TEM. Our active collaboration with Prof. Xiaodong Zou of Stockholm University has been fruitful in gathering 3DED data , helped by Tayyaba Malik.
EELS
The precise and consistent liquid thickness of our Nano Channel Chip, makes it ideal for EELS in liquid. Our closest partner research group led by prof. Kristian Mølhave and in collaboration with assist. Prof. Murat Yesibolati presents an exemplary case of utilizing EELS to quantify the electron inelastic mean free path (IMFP) in water, achieved by employing electron energy loss spectroscopy (EELS) within the context of a transmission electron microscope (TEM).
DOI: 10.1039/d0nr04352d
4D-STEM
With Insight Chips’ Nano Channel Chips, performing 4D-STEM in liquids is now simple and highly reproducible. To showcase this feature we show here, in collaboration with Gatan, the dynamic growth of gold crystals using a 0.5 mM HAuCl₄ solution, precisely confined to a 40 nm liquid layer.
With the K3 detector from Gatan and synchronized eaSI software, 162 data cubes were acquired at 8-second intervals, revealing crystal evolution in all orientations across the channel. This seamless integration of precise liquid control and advanced imaging tools opens up new possibilities for in-situ liquid TEM studies.
EDX - now Spectra Ultra compatible
In liquid-cell TEM it is important that these X-rays can escape the liquid-cell and make it to the X-ray detector. The Nano Channel Chip has a wide opening, allowing X-rays to escape with an angle of 60 degrees! In combination with alpha-tilting, the Nano Channel Chip is ideal for high signal to noise measurements using EDX.
DOI: 10.1103/PhysRevLett.124.065502
Holography
The Nano Channel Chip - with its nanometer precise liquid layer confinement - has allow Prof. Kristian Mølhave and assist. Prof. Murat Yesibolati to precisely determine the fundamentally important value of the Mean Inner Potential (MIP) of liquid water.
DOI: 10.1103/PhysRevLett.124.065502
