Modification of silicon oxide substrates with functional ultrathin organic films

The field of micro-electromechanical systems (MEMS) made of silicon has rapidly expanded over the last few years. These miniature mechanical transducers are used in many different areas. Micromachined mechanical sensors include for example pressure, force, acceleration, torque, inertial, and flow sensors. The market for such micromachined mechanical transducers is huge, accounting for the largest part of the overall MEMS market in the recent past. This is likely to continue in the near future. One reason for this interest is reflected in the many areas where MEMS have the potential to bring significant breakthroughs. They will, for example, play an increasingly important role in the areas of health care, e.g as patient monitoring systems, both portable and in hospitals (bio MEMS), and energy (e.g. in the form of micro fuel cell systems based on MEMS technology), areas which are both on the list of the current grand challenges in science.
However, to date MEMS are currently used in low- or medium-volume applications. One of the main obstacles preventing their wider adoption is the need to protect the surfaces of these entities from detrimental environmental influences, such as humidity, to ensure their reliable, long-term performance. There is also a desire to be able to functionalise the surfaces of these entities in an application-specific manner, such as being able to provide a surface which is sensitive to protein adsorption. Despite the many advances that have been made in the field of fabrication of MEMS, there remains a need to improve the ability to reliably chemically coat or selectively functionalise these surfaces as this often affects the reliability and performance of MEMS.
The project will contribute to the basic knowledge of surface chemistry in general, with novel reactions performed at silicon oxide surfaces in solution and in the gas phase. These deposition processes should open entirely new avenues for the coating and functionalisation of silicon oxide surfaces. A versatile and flexible coating procedure in connection with microstructures and MEMS is currently not available, and we will harness the potential of this procedure to allow flexible surface modification. The generation of a successful vapour phase modification methodology is pivotal for the application in connection with MEMS and will lead to their faster and wider adoption, which may have significant potential impact on fields such as healthcare and energy. The project therefore also contributes to ensuring that the UK will play a significant role in the MEMS market on a long term scale.

The planned methodologies are relevant to many technological processes and may be directly exploited for applications where a tailored interaction between siliocn oxide surfaces and their environment is required. It is hoped that successful experiments will initiate the adaptation of similar systems by other researchers to explore further the potential of this approach.

In addition to the preparation of ultrathin organic films from solution, we also plan to apply films from the gas phase; this process will be applicable to a high number of substrates simultaneously and will be suitable to coat small structures such as MEMS. This is of high relevance for industrial applications since wet chemistry is often not desirable on such scales for technical, economic, and ecological reasons.
It is therefore hoped that the results will initiate the adaptation of similar procedures by industry. The project sits squarely on the interface between materials and surface chemistry and the insights, scientific results and training that derive from the programme will contribute significantly to the current development of MEMS devices.

Potential beneficiaries are therefore the academic community as well as the industrial sector of MEMS. As a consequence this methodology will be beneficial for society in general if the methods developed will be used in connection with MEMS for example in areas such as health care and energy in the future.