Biomedical Engineering Reference
In-Depth Information
16.5.1
Gray-Scale Imaging Array
The properties of BR make it an attractive material to imaging purposes. Wild-type BR
offers high quantum yield and repeatability (8). The chemical environment of the BR mol-
ecule defines its absorption characteristics and sensitivity to photon energies (31). The
wavelength of maximum absorbance for the wild-type BR is 412 nm (dark-adapted BR
(32)) or 568 nm (light-adapted BR (32)). Therefore, the absorption spectrum of BR is close
to the one for the
l
-cones in the human retina (20).
The gray-scale BR imaging array consists of (i) a two-dimensional array of electrodes
on the printed circuit board (see Figure 16.4a), (ii) continuous BR film on top of the elec-
trode array, and (iii) continuous layer of gold. The concentration of the wild-type BR after
extraction and concentration was 29.2 mg/ml. The final concentration of BR after mixing
it with the solution of PVA and phosphate buffer was 8.32 mg/ml. The solution was
spread on top of the printed circuit board, and the PM fragments were immobilized by
the gelation of PVA. A thin layer of gold was sputtered on top of the BR-PVA film to form
a counter electrode. The complete gray-scale BR imaging array is shown in Figure 16.4b.
(a)
FIGURE 16.4
(a) The printed circuit board for the imag-
ing array contains 7
5 electrodes of size
5
5 mm. (b) The wild-type BR-PVA thick
film and a thin layer of gold are processed
on top of the board to form the gray-scale
imaging array.
(b)
