Latvijas Universitātes Cietvielu fizikas institūta, Doktorantūras skolas „Funkcionālie materiāli un nanotehnoloģijas” zinātniskais seminārs, LU CFI, Ķengaraga ielā 8, 2.stāva zālē ceturtdien 6. septembrī pie mums viesosies CAMART2 projekta partnera RISE studenti, kuri pastāstīs par saviem pētījumiem.
Blood age determination by enzymatic degeneration & Amphetamine detection with SiC-Graphene sensors
Patric Elf (KTH) and Johnny Jussi (Rise Acreo)
Law enforcement is always in demand for new methods to secure evidence or improve the accuracy of the evidence gathered to be certain that the correct individuals get put on trial. Trials and the gathering of evidence can however often be a costly affair and as such new and cost-effective new methods are always sought after.
This presentation is about two projects aimed at the forensic sciences and two distinct applications. The first part is a project intent on increasing the molecular knowledge about forensic chemical and biological samples with the scope of developing a rapid (on-site and portable) forensic detection kit. With such, the objective is to push the limit for what is possible to analyse digitally on a crime scene, such as the age of latent fingerprints, the age of blood traces and analysis of low concentrations of drugs. The specific objectives of the project mirror the central needs of the National forensic centre (NFC), with the purpose of quicker turnaround times and more efficient use of NFCs resources. The most promising venue has so far been to determine the age of blood traces by utilizing the fact that biomolecules found in blood fields a strong age dependence. Four different enzymes (ALT, LDH, CK, AST) were investigated in terms of age and activity by letting blood serum with the added enzymes dry for a period time and further examined with an absorbance plate reader and activity assay kits. It was clear from the results that all enzymes, except for AST, showed a decrease in activity which can be correlated to time of deposition – AST was inconclusive. A suitable path forward is therefore to utilize biomarkers to bind to the specific enzymes and perform further measurements. A plausible biomarker for this venue is Quantum dots, due to their inherent long shelf life, strong fluorescence and narrow emission.
The second part of the presentation will focus on the detection of amphetamines and amphetamine derivatives with the use of SiC-Graphene chips. Where a graphene 2” wafer first was supplied by Graphensic AB, epitaxially synthesized by means of Si sublimation from semi-insulating (SI), Si-face, on-axis, 4H-silicon carbide (SiC) substrates. At Acreo, rectangular sensors were produced from the wafer where first five concentric roundels were etched away before an anchoring layer of titanium and gold was added to increase the adhesion to the Graphene, this effectively causes a direct contact for the metal to SiC as well as metal to graphene. The middle roundel was further left open, i.e. not covered with metal, wherein needle probes can be attached for electrical measurements. With this setup, alongside a flow chamber and pump system, it was found that the sensor can detect amphetamine and amphetamine derivatives by photoactivation.
This project is a collaboration between KTH, NFC and Acreo, and is being presented by Patric Elf, student at KTH and Johnny Jussi, industrial PhD student at Acreo.
Reliability of Silicon Carbide based wireless pressure sensors in harsh environment
Sébastien Le Briz (Rise Acreo)
The harsh environment of a combustion chamber (tens of MPa, hundreds even thousands of degrees Celsius, aggressive mixture) makes difficult any measure of the conditions except for laboratory experiments. By its superior mechanical (almost as hard as diamond)) and thermal (melting point at 2800°C) properties, Silicon Carbide (SiC) can be used for a new class of sensor. Such a device is being developed at Rise Acreo. By combining the properties of SiC and the physics of a Fabry-Pérot etalon, the chip could measure pressures up to 35 MPa while enduring the harsh environment of a combustion chamber.
Several MATLAB scripts were written to model the sensor, especially the membrane deflection and the overall reflectance.
A pressure test stand is used for testing the chip pressure’s response with pressures up to 15 MPa while an oven enables an annealing to test the temperature resistance. Several chips and variants have been successfully tested.
Sébastien Le Briz Aerospace studies at ESTACA, French engineering school Trainee at Rise Acreo