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Research Programme 1 (RP1)

RP1 - Devices and Materials
Programme Leaders: Prof. Dermot Diamond and Dr. Cian O'Mathuna

Context and Objectives

The materials component of this RP is focused on understanding the molecular basis for observable characteristics, and generating new ‘adaptive’ materials (WP1.1); i.e., materials whose characteristics can switch dynamically between various states that allow manipulation of fundamental characteristics such as surface energy, polarity, dielectric constant, colour, chemical/biological activity etc. The existing paradigm is to produce materials with (as far as possible) tailored consistent properties. In contrast, adaptive materials will become critical components of more complex structures that are capable of self- or externally-triggered activation between states (swell/contract, block/enable molecular transport, switch on/off molecular binding). As part of the devices component of this RP, these structures will be integrated into next generation sensors at the sensing device level (WP1.3). New approaches to fluid handling will be investigated specifically in the context of providing orders of magnitude improvements in characteristics such as energy/reagent consumption, and controlled transport for sampling, reagent/standard addition and calibration in biomimetic fluidic manifolds (WP1.2). The focus on power minimisation and controlled functionality will extend to circuit design, leading to close integration of circuitry with adaptive materials and fluid handling (WP1.4), but also to a dedicated design effort for other sensor modalities (e.g. audio-visual) that present significant future challenges for configurable sensor platform development. This integrated research programme will have strong links to the Platforms and the Sensor Communities RPs, and to the demonstrator projects, through the provision of fundamental building blocks for more sophisticated ‘platform’ devices.

Work Packages

WP 1.1: Functional Molecular Materials

This WP focuses on several approaches to building multi-functional molecular materials. This will provide the molecular components that will be integrated into sensing platforms and evaluated in demonstrators by activating/deactivating switchable surfaces remotely from measurement to passive state, for example. This requires synthesis, characterisation and application of photoswitchable materials such as spiropyrans/spirooxazines. Integration of photoswitchable and electrochemical switchable materials into nano/microstructured substrates is another key challenge; e.g. micro/nanoporous silica monoliths or polymer beads and micellar structures that provide new ways to perform analytical measurements in a very flexible manner. Finally, a variety of strategies will be pursued to provide selective recognition capabilities at the molecular level, based on size/shape recognition, and using one or more of hydrogen bonding, electrostatic, covalent, acid-base interactions in a pre-organised structure.

WP 1.2: Fundamentals of Microfluidics

New approaches to fluid handing will enable us to perform complex analytical tasks such as sample preparation, processing, transport and detection, using extremely small volumes in a highly controlled micro/nano-environment. The objective of this WP is to provide a critical building block for lowpower, long-term deployable chemo/bio-sensing devices via new materials with tailored surface and bulk properties; e.g. surface energy, polarity, porosity, permeability, wettability etc. A key challenge in this respect is the development of microfluidic manifolds designed for specific analytical measurements in rigid and soft polymer formats. Other challenges include: integration of soft polymer pumps and valves (e.g. based on controlled redox behaviour of conducting polymers) into microfluidic manifolds to provide low-power biomimetic platforms capable of performing complete assays; functions to include sampling, transport, calibration, detection, and waste storage; integration of optical and electrochemical sensors onto biomimetic platforms to provide detection and self-diagnostic capabilities.

WP 1.3: Sensing Devices

Research in this WP will focus on the creation of sensor platforms capable of performing an analytical measurement. These will range in sophistication from relatively simple LED-based chemo-sensors to autonomous, analytical platforms capable of aquiring and processing a sample (e.g. adding specific reagents, filtering), transporting the sample to a detector, performing measurement and calibration. The workpackage will incorporate outputs of WP1.1 into simple devices for assessment of their performance characteristics. Particular attention will be focused on developing configurations and adding functionality to emerging detector technologies, based on non-contact conductivity and spectroscopic detectors, which can provide chemical information on samples without the requirement of direct exposure of a sensing membrane/film. Key challenges include: assessment of new sensing materials generated in WP1.1 in terms of sensitivity, selectivity, lifetime, LOD, etc; investigation into multifunctional capabilities such as the effect of electrochemical and optical switching of conducting redox and photo switchable surfaces on binding behaviour; development of new sensing approaches targeting low power and highly compact configurations; assessment of emerging transducer technologies (e.g. ultra-sensitive non-contact conductivity (liquid phase) and IR-array detectors (Gas phase) for monitoring the chemistry of their environment).

WP 1.4: Configurable and Energy-Aware Hardware

This WP will consider the device design implications of the algorithmic work carried out in the Sensor Communities and Contextual Content Analysis RPs. The motivation is to ensure that the processing developed there can ultimately be pushed out to a sensor device – a key consideration in any real future deployment. Configurability is a key challenge, as processing blocks will need to be re-used in a variety of different sensor nodes and configurations. Work will target both existing mote-type platforms but also next generation Wireless Multimedia Sensor Network (WMSN) nodes; e.g. ‘media-motes’. Mote-based work will concentrate on issues such as 3D assembly using stackable circuits or foldable flex circuitry with flip-chip assembly and flexibility, adaptability, reconfigurability and power-budget minimisation of microcontroller and DSP platforms for control, data processing, encryption and power management. For media platforms key challenges include designing hardware architectures for commonly used computation/power demanding media processing operations and development of configurable architectural/hardware and algorithmic/software application interfaces that can be used to configure overall media processing functionality.

Novelty

There are as yet few examples of field deployments involving chemical sensors with more than a few nodes. Major research efforts world-wide are either centered on the engineering and computing questions, or on fundamental sensor/materials research. For example, the NSF Centre for Embedded Networked Sensing (CENs) led by Prof. Deborah Estrin at UCLA is one of the largest efforts worldwide, with most of the research effort being focused on networking and power management issues using limited scale deployments of physical transducers (temperature, vibration, light etc.) [1]. Recently, some research on chemical sensors and biosensors has been integrated into the centre’s project portfolio, but this is relatively conventional, for example targeting electrochemical sensors for nitrate and lab-on-a-chip devices [2]. In contrast, CSEM (Neuchatel, Switzerland) is focused on fundamental and applied materials research from a micro/nano-fabrication and microsystems perspective [3]. Others like the Center for Bioelectronics and Biosensors, led by Prof. Joseph Wang at the Biodesign Institute in Arizona State University, and the Intelligent Polymer Research Institute led by Prof. Gordon Wallace at the University of Wollongong, Australia [4], are more focused on fundamental chemo/bio-sensor [5] and materials [6] research, and functional polymer materials [7] and devices [8], respectively.

We believe that the really exciting research space that will give rise to future disruptive technologies lies within, and between, these traditionally disparate domains. Perhaps the single most important reason why chemo/bio-sensing has not been integrated to any real degree into wireless sensor networks deployments lies in stability limitations and the associated need to calibrate regularly. In this research programme, we will therefore integrate fundamental materials research (stability) with microfluidics (low-power calibration) to make new robust chemo/bio-sensors, integrated with the latest low power circuitry and management algorithms. These devices will become a key ‘sensor’ building block of for RP3, the Platforms research programme, in which wireless communications capabilities will be added and scale-up issues addressed for wearable sensors and environmental sensing deployments in the demonstrators. Looking to the future and considering the rising interest in Wireless Multimedia Sensor Networks (WMSN) [9][10] that further extends sensing capability with very challenging data modalities, we will also lay the foundations for architectures for next generation media sensor nodes. Novelty here lies in developing architectures for generic configurable data processing blocks that can be leveraged to perform multimodal analysis on the node – a topic that to date has really only been investigated in the mobile device research community, and through merging of imaging technologies and colorimetric chemo-sensing materials.

References:

[1] S. Shenker, S. Ratnasamy, B. Karp, R. Govindan, and D. Estrin, ACM SIGCOMM Computer Communication Review, vol. 33, no. 1, pp. 137–142, 2003.
[2] (2006) Centre for Embedded Networked Sensing (CENs). [Online]. Available: http://www.cens.ucla.edu/
[3] (2006) CSEM annual report. [Online]. Available: http://www.csem.ch/fs/annualreports.htm
[4] (2006) Intelligent Polymer Research Institute. [Online]. Available: http://www.uow.edu.au/science/research/ipri/
[5] (2006) Prof. Joseph Wang (home page). [Online]. Available: http://www.public.asu.edu/~jwang85/index.htm
[6] J.Wang, M. Scampicchio, R. Laocharoensuk, F. V. O. Gonzalez-Garcia, and J. Burdick, “Magnetic tuning of the electrochemical reactivity through controlled surface orientation of catalytic nanowires,” J. Am. Chem. Soc., vol. 128, no. 14, pp. 4562–4563, 2006.
[7] J. Madden, J. Barisci, P. Anquetil, G. Spinks, I. Hunter, and G.Wallace, “Fast carbon nanotube charging and actuation,” Advanced Materials, no. 18, pp. 870–873, 2006.
[8] C. Wang, A. Ballantyne, S. Hall, C. Too, D. Officer, and G. Wallace, “Functionalized polythiophene-coated textile: A new anode material for a flexible battery,” Journal of Power Sources, no. 156, pp. 610–614, 2006.
[9] J. Campbell, P. Gibbons, S. Nath, P. Pillai, S. Seshan, and R. Sukthankar, “IrisNet: an internetscale architecture for multimedia sensors,” in Proceedings of the ACM Multimedia Conference, 2005.
[10] I. F. Akyildiz, T. Melodia, and K. R. Chowdhury, “A survey on wireless multimedia sensor networks,” Computer Networks (in press), 2006.