Sensor Chip Assembly

ROICs are used with arrays of detectors to make a sensor chip assembly, or SCA. The primary application of SCAs is to create images. Two-dimensional (2D) SCAs are the latest in the evolution through the four stages shown in Figure 7.1. 

Figure 7.2 The sensor chip assemblies (SCAs) comprise a detector array interconnected, or hybridized, to the readout integrated circuit (ROIC).

Direct detection of a cytokine protein, recombinant human interferon-y, using an IBIS SPR sensor is presented in [60]. Several types of sensor chip coatings, including self-assembled monolayers and hydrogel-derivatized SAMs, were characterized in terms of their ability to resist non-specific adsorption from plasma. The best results with respect to plasma adsorption and surface regenerability were obtained with antibodies immobilized on the dextran-modified 11-mercaptoimdecanoic acid SAM. The detection limit for detection of human interferon-y in 1 100 diluted plasma was established at 250ngmL . ... 

FIGURE 1.12 Chip assembled on standard TO-8 package. (Reprinted from Sens. Actuators B, 58, Horrillo M.C., Sayago L, Ares L., Rodrigo J., Gntierrez J., Gotz A., Gracia I., Fonseca L., Cane C., and Lora-Tamayo E., Detection of low NO2 concentrations with low power micromachined tin oxide gas sensors, 325-329, 1999, with permission from Elsevier.)... 

Figure 1 Strategies for GPCR attachment to dextran matrix. The interactive surface of a sensor chip consists of a self-assembled dextran monolayer (SAM) that bears functional groups to allow interaction of different compounds. For GPCR capture on the sensor chip surface, several strategies are used including direct binding to the dextran surface of monoclonal antibodies (A), avidin (B), GAG (C), or LVP (D).

ACA flip chip technology has been employed in many applications where flip chips are bonded to rigid chip carriers (13). This includes bare chip assembly of ASICs in transistor radios, personal digital assistants (PDAs), sensor chip in digital cameras, and memory chip in lap-top computers. In all the applications, the common feature is that ACA flip chip technology is used to assemble bare chips where the pitch is extremely fine, normally less than 120 /rm. For these fine applications, it is apparently the use of ACA flip chip instead of soldering which is more cost effective. 

The methodology mentioned above can be used to asymmetrically end-functionalize CNTs with ssDNA and cDNA chains onto their opposite tube ends, which can be very useful for site-selective self-assembling of CNTs into many novel functional structures for various potential applications, including nanotube sensors and sensor chips. In a similar but independent study, asymmetric end... 

We further addressed the use of the nucleic acids as biopolymers for the formation of supramolecular structures that enable the electronic or electrochemical detection of DNA. Specifically, we discussed the use of aptamer/low-molecular-weight molecules or aptamer/protein supramolecular complexes for the electrical analysis of the guest substrates in these complexes. Also, nucleic acid-NPs hybrid systems hold a great promise as sensing matrices for the electrical detection of DNA in composite three-dimensional assemblies. While sensitive and selective electrochemical sensors for DNA were fabricated, the integration of these sensor configurations in array formats (DNA chips) for the multiplexed analysis of many DNAs can also be envisaged. 

Therefore, another type of planar glucose biosensor with Pt electrodes on a sihcon substrate has therefore been developed for in vivo measurements [61]. The enzyme glucose oxidase was immobilized by the well known GDA-BSA method and the whole sensor was covered subsequently by a polyurethane membrane. This sihcon chip has to be sawed and assembled on a flexible carrier for in vivo application, the assembled catheter was successfully evaluated in rats [79]. This sensor gives encouraging results in aqueous solutions and subcutaneous apphcations. Drawbacks of this include the complicated mounting and assembling procedures which are difficult and cumbersome. 

The sensors of the electronic nose are assembled in an array. The array is normally a small electronic unit that integrates the different sensors into a practical circuit card or another appropriate system that is easy to insert into the electronic nose instrument. If the array is to be used in a flow injection setup the unit also comprises a flow cell compartment with minimal volume. The system depicted in Fig. 2 shows how MOS and MOSFET arrays are integrated in a flow injection system [11]. Larger arrays can be integrated into silicon chips, as described for CP sensors where, for example an ASIC chip with 32 sensors has been fabricated with BiCMOS technology and having an area of 7 x 7 mm [18]. If the array is be inserted in the headspace volume of a bioreactor, the technical solution is a remote array probe that can be placed in a gas sample container [19]. 

Using PAA as the starting point, a self-assembly DNA-conjugated polymer was prepared for DNA chip fabrication. The amounts of ssDNA and PDPH in the polymer were determined by absorption measurements to be equivalent to 1/714 [molecule/monomerunit] and 1/46 [molecule/monomerunit], respectively. A 20-mer ssDNA as P-1 DNA and PDPH for self-assembled immobilization were covalently attached to PAA as side chains. After self-assembled immobilization of the DNA-conjugated polymer on the gold surface of a sensor, the P-1 DNA chain was hybridized to a 34-mer ssDNA as P-2 DNA, which had a sequence fully matched to the desired target DNA. Analysis of the first hybridization (between P-1 and P-2 DNA) and of the second hybridization (between P-2 and the target DNA) was done by fluorescence measurements. 

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