The Computer Screen Photo-assisted Technique (CSPT) utilizes a computer screen as a
light source and a web camera as a detector for optical measurements. This provides a
ubiquitous instrumentation for several bioanalytical situations. In the present contribution
we first describe CSPT briefly, demonstrate the possibility to make optical fingerprinting
of fluorescent color indicators and give a mini-review of our recent demonstration of
CSPT based surface plasmon detection. Although we have no results yet specifically
aimed at real biosensing, we point out the possibilities to make affinity based biosensing
Detection and classification of fluorescent dyes are demonstrated using a computer screen photo-assisted technique (CSPT). This technique has previously been demonstrated for analyzing fluorescence from 96 wells microtiterplates (200 μl per well) and from a single cuvette with some optics to enhance sensitivity. In this work a custom designed array of wells with a volume of approximately 1 mu;l is used. In order to measure such small volumes without saturating the detector, the transmitted light is masked by placing the sample between two crossed polarizers. This arrangement blocks nearly all the transmitted light, while the emitted light, which is nearly unpolarized, can still be detected. The lowest amount (concentration x volume) of analyte detectable in this setup is about 40 times smaller than in the previous setups.
The volume change that the conducting polymer polypyrrole (PPy) undergoes upon electrochemical oxidation and reduction can be used to make microactuators. We have made microactuators based on a PPy/Au bilayer. These actuators have been combined with other micromachined structures to make biomedical microdevices. Using an area of bilayers one can potentially arrest (nerve) fibers. They can also be used to close a micrometer sized cavity with a lid. In addition, we demonstrate a microrobotic arm that may be developed for the manipulation of small particles.
A surface plasmon resonance (SPR) apparatus was used to investigate blood plasma coagulation in real-time as a function of thromboplastin and heparin concentrations. The physical reason for the SPR signal observed is discussed and 3 different models are proposed. The response curves were analyzed by multivariable curve fitting followed by feature extraction. Interesting parameters of the sigmoid curves were lag time, slope and maximum response. When thromboplastin concentrations were increased, the lag-time decreased and the slope of the curve increased. A prolonged clotting time was followed mostly by increased maximum response, with exception for samples with no or very little thromboplastin added. High heparin concentrations changed the clotting kinetics. As seen from the lag-time vs. slope relation. Atomic force microscopy pictures of sensor surfaces dried after completed clotting, revealed differences in fibrin network structures as a function of thromboplastin concentration, and fiber thickness increased with lower thromboplastin concentration. The results correlate well with present common methods.
Human immunoglobulin G (IgG) and colostrum immunoglobulin A (IgA) were absorbed to hydrophobic silicon and the deposition of complement (C) was studied by ellipsometry- antibody techniques after incubation at 37 degree(s)C in human serum for up to 1 hour. In parallel experiments soluble iC3b, C4d and Bb were detected by ELISA-techniques. IgG coated surfaces rapidly activated the classical pathway and caused deposition of anti-C3c, antiproperdin, and during short serum incubation times also of anti-C1q and anti-IgG. The IgA-coated surfaces activated the alternative pathway and displayed a lag phase in the complement protein deposition. Anti-IgG, Clq, -C4, -factor H and -factor B were not deposited into IgA-surfaces at any time. Ellipsometry and antibody techniques offer a convenient and rapid means to display activation of the complement system by solid light-reflecting surfaces and facilitate a time-resolved determination of the activation pathway(s).
An optical three-dimensional multilayer memory device based on the effipsometric principle is presented. The possibilty to utilize the flexibility of organic layers e. g. conducting polymers will be discussed. PRINCIPLES A concept of an optical three-dimensional memory device based on the ellipsometric principle1 is presented. This " effipsometric" memory is a thin film multilayez device with an optical read-out. The information is contained in the optical properties of thin films and is read by analyzing the state of polarization ofa polarized light beam reflted at oblique incidence from a memory cell. The device is here examplified with the case of two layers on a substrate which is equivalent to a memory cell capable of storing one 2-bit word. If the optical properties of the two layers can be controlled independently we can generate 4 different states of polarization in the reflected beam corresponding to the " logical states" (0 (0 (1 and (1 ofthe memory cell. In a generalization to n layers it is possible to have 2fl different states. In other words an n-bit word can be stored at one location. Fig. 1. An optical memory device having 2-bit memory cells. With an ellipsometric read-out the state of polarization in the reflected beam is described by the two ellipsometric angles and These angles can be determined with a precision better than 0. 01''. The lateral resolution limiting the memory