Stiction-Free and Tuneable Nano-Electro-Mechanical Systems Incorporating Liquid Crystals

Lead Research Organisation: University of Southampton
Department Name: Optoelectronics Research Centre (ORC)


Nano-electro-mechanical systems (NEMS) are integrated miniature devices that can sense or actuate on the nanoscale, while generating observable effects on the macroscale. They are beginning to shape into one of the key technologies of the 21st century, which has the potential to revolutionize both industrial and consumer products, transforming the way we live and work through a multitude of applications (ranging from displays, smart phones, portable electronics and computer peripherals to cars, medical diagnostics and therapy, metrology and navigation). However, nanoscopic mechanical motion underpinning the functionality of such systems is often affected by a number of parasitic effects and the chief among them is stiction - unintentional adhesion of moving parts leading to a catastrophic failure of the devices. Correspondingly, the ability to engage and control reliably mechanical movements in NEMS is the main challenge of the technology.

We believe that by combining NEMS with liquid crystals we can meet this challenge in a simple yet efficient manner and develop a new generation of NEMS - stiction-free hybrid nano-electro-mechanical systems, which will feature dynamically adjustable behaviour and field-programmable functions. Our approach exploits elastic distortions in liquid crystals coupled to nanoscopic mechanical motion in operating NEMS. By engaging transitions between various structural phases of liquid crystals and their susceptibility to a wide range of stimuli (i.e. heat, light, electric and magnetic fields) we will introduce a mechanism for tuning dynamically the response characteristics of the resulting hybrids and eliminate the need for additional integrated circuitry, thus, reducing the overall complexity and cost of the devices. A broad spectrum of structural transitions exhibited by liquid crystals (when confined at the nanoscale) should further enrich the behavior of such hybrid NEMS as actuators, sensors, relays, re-configurable metamaterials and plasmonic circuits, making the development of adaptive and 'smart' nanosystems a practical proposition.

Planned Impact

The proposed project offers strong technological impact by addressing current challenges and introducing new capabilities in the field of microsystems and, in particular, nano-electro-mechanical systems (NEMS). Given that NEMS technology is starting to occupy a central position in our daily life (think of smart phones, displays, cars, telecom and internet, heart pacemakers and hearing aids etc.), the successful outcome of our research program will provide the UK's relevant industries with a competitive advantage that will ultimately translate to improvement in the quality of life.

The project will also contribute directly to applied and fundamental sciences by

- providing a platform for engineering smart photonic media with strong nonlinearity, and dynamically and spatially tuneable optical properties;

- expanding our knowledge on mechanical behaviour and ordering of liquid crystals (LCs) at the nanoscale through systematic study and characterization of LC-NEMS hybrids;

- introducing a new exciting area of research, which interfaces elastic and mechanical response of soft and (structured) hard matter at the nanoscale.
Description We discovered a new optical effect while developing and characterizing a metamaterial-based test platform for our study on stiction suppression in nano-electro-mechanical systems. The effect manifests itself as the appearance of new spectral components in the optical response of metamaterials of a certain type under incoherent illumination. Previously unseen in metamaterials the effect has also no direct analogue in natural optical materials, and we envisage it may be used to enhance the functionalities of nano-electro-mechanical optical sensors and display pixels exploiting our metamaterial platform.

We identified a new promising optical platform for studying stiction suppression in micro- and nano-electro-mechanical systems. It is based on a 1D photonic crystal terminated by a nanostructured metallic metasurface, and exploits the so-called Tamm plasmons - localised optical excitations confined at the interface between the photonic crystal and metal. Our approach enables external access to and control of Tamm plasmons, which can be used for precision optical detection of out-of-plane actuations of micro- and nano-electro-mechanical systems (such as cantilevers) integrated with a metal-coated photonic crystal as the base.
Exploitation Route Combined with a photodetector, the metamaterial platform that we developed here represents a very simple and compact (and mechanically tuneable in the future) optical device that will enable quick quantitative assessment of the spatial coherence of light. Such a device will measure the transmission coefficient at the wavelength of interest under partially coherent illumination, which is a linear function of the coherence length. The rest of the parameters, namely the transmission coefficient under spatially coherent illumination and the extent of the nanostructure's nonlocal scattering, can be determined only once, during the initial characterization of the device. Other possible applications will rely on the ability of the metamaterial to selectively transmit or block spatially incoherent light, and hence include the enhancement of optical imaging, vision, detection, and communications.

The demonstrated ability to control externally the wavelength of Tamm plasmons opens up a viable route to exploiting this resonant optical state in many real-life applications, including optical switching, enhancement of optical non-linearity, lasing and light emission, and surface-enhanced spectroscopy.
Sectors Aerospace, Defence and Marine,Digital/Communication/Information Technologies (including Software),Energy,Environment

Description Tamm plasmon modelling 
Organisation Taras Shevchenko National University of Kyiv
Country Ukraine 
Sector Academic/University 
PI Contribution Experimental characterization of a new, Tamm plasmon-based testing platform.
Collaborator Contribution Theoretical analysis and modelling of a new, Tamm plasmon-based testing platform.
Start Year 2019
Description Thin film deposition 
Organisation Center for Physical Sciences and Technology
Country Lithuania 
Sector Public 
PI Contribution Provided expertise in -design, fabrication and characterization of optical metasurfaces; -hybridization of metasurfaces with photonic crystals and liquid crystals. Provided feedback on the performance and quality of the samples fabricated by the collaborator.
Collaborator Contribution Designed and fabricated components of a new, Tamm plasmon-based optical platform, which would be used in the study of stiction suppression in micro- and nano-electro-mechanical systems.
Start Year 2019