The ability to capture, recognize and respond to chemical and mechanical cues is the most important, most diverse and evolutionary the oldest tuning mechanisms out there. Plants, mushrooms and bacteria relay only on this ability to gather information, communicate and adapt. This section groups EPFL’s research projects that get inspired by the ability of organism, and natural materials to sense chemical and mechanical cues and respond to them for development of 1) new sensors, the biosensors, with high degree of sensitivity capable of detecting wide range of compounds, and 2) intelligent materials capable of monitoring, self diagnosis and adaptation.
The objective is to explore the possibility of using spider dragline silk as sensing element for fibre-based biosensors by transmitting light through silk fibre and monitoring the change in the silk’s optical properties induced by biochemical compounds. The fast response and high sensitivity of the silk fibre in response to polar compounds paves the way for promising applications for biochemical sensing.
Nervous system of composite structures
Several projects deal with the introduction of fiber optic sensors in composite structures, quite similarly to a nervous system in the human body. These thin embedded Fiber Bragg Grating sensors send information on local strains and temperature in the structure, which can be used for design validation, performance development and real-time monitoring. A good example was the integration of these sensors in the Alinghi America’s cup challenges in 2007 and 2010 (http://discovery.epfl.ch/page-105680-fr.html)
ENCOMB project (2011-2015)
The EU-FP7-ENCOMB project deals with the Extended Non-Destructive Testing of Composite Bonds. The central problem addressed within ENCOMB is the development of advanced non-destructive testing (NDT) methods for a reliable quality assurance concept for adhesive bonding of carbon fiber reinforced polymers (CFRP) structural aircraft components. The primary objective of ENCOMB is the identification, development, and adaptation of methods suitable for the assessment of adhesive bond quality. The EPFL team contributes by fabricating Bragg grating optical fiber sensors in 125-micron and 50-micron-diameter optical fibres, their integration into different CRFP samples and bond layers, and their characterisation during curing, and during service at different temperatures and exposure to water and contaminated water. Mechanical models are being developed simulating the behavior of CRFP, adhesive, and sandwich structures under thermal load and water diffusion.
Project Leaders: Dr Hans Limberger (Optical Fiber Device group), Prof. John Botsis (Laboratory of Applied Mechanics and Reliability Analysis), Prof. Veronique Michaud (Laboratoire de technologie des composites et polymères)
Sensing and accurately quantifying small molecules in biological samples remains an unmet challenge in many areas related to health and biotechnology. While very promising sensing platforms have been developed, the limitation remains in the ability of designing high affinity and specific small molecule receptors that can be used in these sensing platforms. To accomplish this project our laboratory will approach this problem using both chemical biology and computational protein design approaches.
Relevant references: Kambe T, et al. JACS (2014); Niphakis MJ et al., Cell (2015) and Griss R et al., Nat Chem Biol.
Silicone embedded distributed piezoelectric sensors for contact detection
The objective of this project is to design a soft, flexible, thin substrate capable of detecting contact. Such system can be used for wearable applications thus enabling the evaluation of external forces and for functionalizing the surface of surgical tools or robotics system allowing fast response contact detection. Layer by layer fabrication technique joined with materials selection allow the achievement low fabrication cost, scalability, fast prototyping and fine tuning of sensor transfer function.
Biomimetic Pieris rapae’s Nanostructure and Its Use as a Simple Sucrose Sensor
We present the replication of the Pieris rapae butterfly optical structure. This butterfly has white wings with black spots. The white coloration is produced by light scattering on pterin beads ranging from 100 to 500 nm whereas black spots correspond to areas without pterin beads, thus revealing a highly pigmented layer underneath. In order to mimic the butterfly wing structure, we deposited SU-8 beads produced by electrospraying on a black absorbing layer made of black SU-8. We thereby replicated the optical effect observed on Pieris rapae. Additional experiments showed that the white coloration replication is a structural color. Finally, we further demonstrate that these optical engineered surfaces can be used for sucrose sensing in the range of 1 g/L to 250 g/L.
Full article here.