Biological olfaction outperforms chemical instrumentation in specificity, response time, detection limit, coding capacity,
time stability, robustness, size, power consumption, and portability. This biological function provides outstanding
performance due, to a large extent, to the unique architecture of the olfactory pathway, which combines a high degree of
redundancy, an efficient combinatorial coding along with unmatched chemical information processing mechanisms. The
last decade has witnessed important advances in the understanding of the computational primitives underlying the
functioning of the olfactory system. EU Funded Project NEUROCHEM (Bio-ICT-FET- 216916) has developed novel
computing paradigms and biologically motivated artefacts for chemical sensing taking inspiration from the biological
olfactory pathway. To demonstrate this approach, a biomimetic demonstrator has been built featuring a large scale sensor
array (65K elements) in conducting polymer technology mimicking the olfactory receptor neuron layer, and abstracted
biomimetic algorithms have been implemented in an embedded system that interfaces the chemical sensors. The
embedded system integrates computational models of the main anatomic building blocks in the olfactory pathway: the
olfactory bulb, and olfactory cortex in vertebrates (alternatively, antennal lobe and mushroom bodies in the insect). For
implementation in the embedded processor an abstraction phase has been carried out in which their processing
capabilities are captured by algorithmic solutions. Finally, the algorithmic models are tested with an odour robot with
navigation capabilities in mixed chemical plumes
A multisensing flexible Tag microlab (FTM) with RFID communication capabilities and integrated physical and
chemical sensors for logistic datalogging applications is being developed. For this very specific scenario, several
constraints must be considered: power consumption must be limited for long-term operation, reliable ISO compliant
RFID communication must be implemented, and special encapsulation issues must be faced for reliable sensor
integration. In this work, the developments on application specific electronic interfaces and on ultra-low-power MOX
gas sensors in the framework of the GoodFood FP6 Integrated Project will be reported.
The electronics for sensor control and readout as well as for RFID communication are based on an ultra-low-power
MSP430 microcontroller from Texas Instruments together with a custom RFID front-end based on analog circuitry and
a CPLD digital device, and are designed to guarantee a passive ISO15693 compliant RFID communication in a range up
to 6 cm. A thin film battery for sensor operation is included, allowing data acquisition and storage when no reader field
is present. This design allows the user to access both the traceability and sensor information even when the on-board
battery is exhausted.
The physical sensors for light, temperature and humidity are commercially available devices, while for chemical gas
sensing innovative MOX sensors are developed, based on ultra-low-power micromachined hotplate arrays specifically
designed for flexible Tag integration purposes. A single MOX sensor requires only 8.9 mW for continuous operation,
while temperature modulation and discontinuous sensor operation modes are implemented to further reduce the overall
The development of the custom control and RFID electronics, together with innovative ultra-low-power MOX sensor
arrays with flexible circuit encapsulation techniques will be reported in this work.
Diffractive Fresnel Lenses (FL) were designed, fabricated and tested. The lens aims for increasing the sensitivity of a Non-Dispersive InfraRed (NDIR) silicon based optical gas system, focusing as much radiation as possible onto the detector. The studied wavelengths are 10.6μm and 3.4μm, which are the main absorption lines for ethylene and ethanol respectively. The lens diameter (5mm) and the focal length (4mm) are fixed by the detector package. Those diffractive lenses are compatible with the planar nature of silicon microtechnology. A theoretical study about the global lens efficiency as a function of the technological constrains and the process complexity has been carried out. Using only three photolithographic masks, eight quantization steps can be etched and a theoretical lens efficiency of 95% can be achieved. Once the devices were fabricated, the focal length and the spot size have been measured.
A micro component for a non-selective NDIR (non dispersive infrared) gas detection system is presented in this work. This device consist of an IR detection module composed of a thermopile and a thin film filter array. The thermopile arrays (up to 4x4) are built on a silicon substrate by bulk micro-machining processes. The whole matrix is built on a thin freestanding silicon oxide/silicon nitride membrane of 2100x2100μm2 defined by anisotropic wet etching. To ensure the existence of hot and cold junctions for each detector we define on the insulating membrane absorbers and ribs, 6μm thick, by heavy boron doping of the silicon underneath. The ribs crisscross the membrane contacting the silicon bulk acting as a heat sink. Absorbers are located in the centre of each individual pseudo-membrane defined by the ribs intersection. Incident radiation heats up the absorber creating a temperature difference that is measured by the thermocouples that are placed between the absorber and the ribs.
On a second chip, the elements of the filter array are fabricated in a matching configuration. The filters are built on a silicon substrate alternating thin films of different refraction index acting like a Fabry-Perot structure with 2-8μm silicon oxide cores. The transmitted filter peaks are not tuned for the detection of any specific substance: they configure a non selective general purpose filter array (400-4000 cm-1), making signal processing and pattern recognition techniques necessary.
Both dies have been fabricated and characterized and have been successfully attached using flip-chip techniques.
The measurements on these devices have been used to build an optical simulation tool that allows the assessment of the whole NDIR system behaviour in operating conditions.
The objective of this ongoing work is the development of a microlab on flexible tag, capable to monitor the quality of the food, during transport, storage and vending. The idea is to bring together different sensor technologies that will be integrated into a data communication environment for online food monitoring during the logistics chain.
The proposed solution is the concept of silicon chips and microcomponents assembled and integrated on top of a flexible substrate acting mainly as a passive interconnect structure.
Three technologies have been identified as necessary to get the final integration:
a) Substrate technology. This technology refers to the realisation of the flexible substrate with the metallic interconnections.
b) Assembly technology to integrate the discrete components on the flexible substrate. The conventional processes are wire bonding, flip chip, and adhesive bonding.
c) Encapsulation technology and windows opening over the gas sensitive areas.
The first flexible tag prototype integrates two different metal oxide sensor arrays with a commercial microprocessor. The dimensions are 43 mm long, 22 mm wide and about 2 mm thick and two metal levels are necessary for the interconnect. The strategy undertaken by the groups involved in this work, consists in the evaluation of different approaches, that combine diverse process sequences and materials, with the final aim of identifying the best solution.
Regarding the substrate technology, the approach realized using Pyralux copper-clad laminated composites, constructed of DuPont Kapton polyimide film with copper foil on both sides, as flexible substrate will be described in this paper. The cupper interconnections are generated by standard photolithography and wet etching and the vias definition in Kapton is performed by femtosecond laser ablation. On the other hand, the assembly technology based on the use of anisotropically conductive adhesives will be also illustrated.
Pressure sensors structures have been fabricated in a commercial CMOS foundry technology using a post-processing for back-side wafer micro machining. In order to predict the sensor response to an externally applied differential pressure, the structure behavior has been simulated by Finite Element Methods. The design and fabrication of test structures for these sensor devices is described. Experimental results obtained using these structures are presented.
The aim of this work is to analyze the thermo-mechanical stresses evolution produced during the fabrication sequence of the multi-level UTCS structure. Several non-linear material models have been taken into account during the process of modeling. We have therefore resorted to the Finite Element Method for the evaluation of such thermo- mechanical stresses that appears in the manufacturing and stacking process. These efforts are made to optimize the product and process design.
A new vertical chip integration is proposed, based on the UTCS concept. It consists in stacking thinned chips on top of a silicon substrate. Lateral and vertical metal interconnections and the thinned chips are embedded in BCB layers. This wafer scale integration technique is presented. Thermal behavior of such stacked structure is also discussed.