Advanced Hybrid Manufacturing Platform for Carbon Nanotube Devices (ADVENTURE)
Lead Research Organisation:
University of Cambridge
Department Name: Engineering
Abstract
Carbon nanotubes (CNTs) have been pivotal in generating industrial interest in nanotechnology. Their success can be quantified by the production volume of CNTs, which is growing exponentially, and is currently estimated at 5000 ton/yr. In part, this success can be attributed to the physical properties of CNTs, some of which are unlike any other engineering material (e.g. Youngs Modulus of 1 TPa, a tensile strength of 100 GPa, thermal conductivities up to 3500 Wm-1K-1). Importantly, the above off-the-chart properties only apply to high quality individual nanotubes whereas most commercial applications require tens to millions of carbon nanoparticles to be assembled into one device. Unfortunately, the mechanical and electronic properties of merit typically drop by at least an order of magnitude in comparison to the constituent nanoparticles once integrated into an assembly. It is therefore critical to develop new manufacturing processes which enable enhanced assembly of CNTs and their integration in devices. Additionally, many applications require CNTs to be interfaced with electrodes for electrical connections, as well as with liquids for sensing, microfluidic and biomedical applications, which typically require various additional advanced manufacturing processes that have several complexities and limitations.
In this EPSRC Adventurous Manufacturing grant, we aim to develop innovative manufacturing techniques capable of creating structured assemblies of carbon nanoparticles with both integrated electrodes and microchannels. This requires the consolidation of manufacturing techniques that has never been attempted previously. It will allow control of structures over multiples length scales:
- At the nanoscale (<500 nm), we will use chemical vapour deposition (CVD) to synthesise large arrays of aligned CNTs and self-assembly to control their organisation.
- At the microscale (50 um - 500 nm), we will use multiple step lithography to define read-out electrodes and define where CNTs are synthesised.
- At the largest scale (1 mm - 50 um), we will use laser processing (short and ultrashort pulses) to define microchannels and the overall chip geometry.
While each of the above manufacturing techniques are well established, bringing these methods together enables the manufacturing of radically new devices. Maintaining compatibilities and alignments between different processes will create new research challenges which will be addressed in this project. Ultimately, this new set of manufacturing techniques form a platform technology that can be used to solve a multitude of engineering problems. We envision the outputs of this proposal to find applications in chemical sensors, biomedical applications, microfluidics and actuators As a demonstrator, this project will develop CNT based thrusters for space propulsion applications.
In this EPSRC Adventurous Manufacturing grant, we aim to develop innovative manufacturing techniques capable of creating structured assemblies of carbon nanoparticles with both integrated electrodes and microchannels. This requires the consolidation of manufacturing techniques that has never been attempted previously. It will allow control of structures over multiples length scales:
- At the nanoscale (<500 nm), we will use chemical vapour deposition (CVD) to synthesise large arrays of aligned CNTs and self-assembly to control their organisation.
- At the microscale (50 um - 500 nm), we will use multiple step lithography to define read-out electrodes and define where CNTs are synthesised.
- At the largest scale (1 mm - 50 um), we will use laser processing (short and ultrashort pulses) to define microchannels and the overall chip geometry.
While each of the above manufacturing techniques are well established, bringing these methods together enables the manufacturing of radically new devices. Maintaining compatibilities and alignments between different processes will create new research challenges which will be addressed in this project. Ultimately, this new set of manufacturing techniques form a platform technology that can be used to solve a multitude of engineering problems. We envision the outputs of this proposal to find applications in chemical sensors, biomedical applications, microfluidics and actuators As a demonstrator, this project will develop CNT based thrusters for space propulsion applications.
People |
ORCID iD |
| Michael Franciscus Lucas De Volder (Principal Investigator) |
Publications
Gregg A
(2023)
Kinetics of Light-Responsive CNT / PNIPAM Hydrogel Microactuators
in Small
| Description | This research has lead to the development of a hybrid manufacturing platform where two top-down manufacturing processes (laser patterning and lithography) are combined with bottom-up nanotube self-organisation. This is a platform technology that can be used for the fabrication of new sensors, actuators and energy storage devices. This approach to combine different manufacturing techniques has not been reported previously and we believe that it could lead to a range of new nanomaterial based applications. |
| Exploitation Route | We are less than two years into the project by have already received substantial interest from colleagues in the UK and abroad who wish to use the developed technology for applications we had not envisioned at the start of the project. This includes, the fabrication of electrodes for Li-Air batteries, the fabrication of electrode for microbial cells, the fabrication of micro pumps and actuators. As this work is published and presented at conference, we expect many more opportunities to take this work forward to arise. |
| Sectors | Aerospace, Defence and Marine,Energy,Manufacturing, including Industrial Biotechology |
| Description | This project has lead to a close collaboration with the Tokyo Institute of Technology. This collaboration not only fosters more opportunities for scientific discovery but also broadens the cultures our researchers are exposed to. |
| First Year Of Impact | 2022 |
| Sector | Manufacturing, including Industrial Biotechology |
| Impact Types | Cultural |
| Title | Hybrid Manufacturing Method |
| Description | During this project we have established a method to integrate 3 different manufacturing processes that have not been combined previously: Lithograhy, Laser processing and chemical vapour deposition of nanotubes. This is a platform technology that will help applying carbon nanotubes in a range of practical engineering applications. We had to overcome important challenges in aligning these processes with each other for which we have developed new approaches that have been successful so far. Laser macro and micromachining methods have been developed to allow for fast device design iteration and manufacturing. Laser macromachining was used to make millimetre-scale features with low positioning requirements (< 1 mm). It is typically used for features such as suspended membranes, propellant channels, and surface treatments. The process was characterised to enable tight etching depth control. Etching accuracy under 1% was achieved during the manufacturing of 100 µm suspended membranes from 500 µm 4 inch silicon wafers. Removing 400 µm depth took 20 min for a surface area corresponding to a disk diameter of 9 mm. This fast-processing time allows for multiple wafers to be processed during the same day. Control surface texturing of the silicon wafers has also been demonstrated with surface roughnesses ranging from ± 20 µm to ± 2 µm. It allows to modify the wettability properties of various parts of the same wafer in the same processing step. Laser micromachining processes were developed to manufacture features smaller than 20 µm compatible with standard photolithographic processes. Repeatable arrays of 45 x 45 holes spaced by 100 µm with an aspect ratio of 20 on a 100 membrane with exit holes diameters of 5 ± 1 µm and entry diameters of 25 µm. The array was aligned to existing lithographic layers with an accuracy of ± 5 µm. Processing the array took 2 min of laser processing. A method was developed to protect the wafer surfaces from contamination during the micromachining occurring in a non-cleanroom environment. The growth of contamination sensitive carbon nanotubes (CNTs) was demonstrated in immediate proximity (< 100 nm) of the micromachining sites. Positioning accuracy of laser machined features at the micrometer-scale is challenging. A process was created to align laser micromachined features to lithographic features with an accuracy better than ± 10 µm. It started with an extensive characterisation of the laser optics properties. The information collected was then used to deform the device designs to compensate for the optics non-linearities. Custom lithographic processes were developed to spin-coat macro and micro machined silicon chips. 2 µm feature size lithography was achieved. It showed that the same lithographic performances are obtainable on macro and micro machined silicon chips as on standard silicon chips with resources commonly available in universities research facilities. The compatibility of CNT microstructures with laser macro and micromachining has been demonstrated. CNT forests with heights from 10 to 200 µm were made. Methods were developed to allow CNTs to be used in devices using thick photoresist (SU-8) layers (> 40 µm). It required lithographic processes such as the spin coating, the soft bake, the post exposure bake and the photoresist development to be optimised to preserve the CNT microstructure integrity while achieving high quality photoresist microstructures. |
| Type Of Material | Improvements to research infrastructure |
| Year Produced | 2022 |
| Provided To Others? | No |
| Impact | To date, we have not been able to fully unlock the potential of carbon nanotubes in many application areas. Often, this is related to manufacturing challenges. While methods to synthesise carbon nanotubes are well established we lack techniques to assemble them into practical devices. The method developed in this project allows for a scalable method to pattern CNTs and connect them with both electronic and microfluidic channels. We have created new CNT structures that are suspended onto thin silicon membranes and have complex structure that are impossible to achieve using other processing methods. We have demonstrated that these structures are particularly useful for sensing applications, which will be published shortly, as well as for actuators, which we are characterising at the moment. |
| Description | Collaboration with the Tokyo Institute of Technology |
| Organisation | Tokyo Institute of Technology |
| Country | Japan |
| Sector | Academic/University |
| PI Contribution | The research carried out in this project was of particular interest to the group of Prof Joon-Wan Kim, who is an expert in the the fabrication of micro pumps and actuators. He supported this project by providing expert advice and both Prof Joon-Wan Kim and one of his PhD students have been making samples to support our work. |
| Collaborator Contribution | Prof Joon-Wan Kim and his research students have been processing silicon wafers using a series of MEMS processing techniques to create both micro pumps and batteries. This allows us to apply the techniques from this project to new types of applications. Also, the research student is applying for a fully funded fellowship to visit my research group, again with the view to support our work and create new exciting applicaitons. |
| Impact | - Follow-up exchange project with exchange PhD student currently under revision - Joint publications are under way - This may lead to more exchange projects with Japan that can lead to better scientific training and broader cultural exposure of our students |
| Start Year | 2021 |