The SpecPhone was designed to be simple, compact, and able to measure concentrations accurately. We designed the housing with 3D CAD software to position the optical elements in a way that facilitates measurements using a standard laboratory cuvette. A schematic of the device is shown below.
An external light source is directed to a slit positioned at the beginning of the light path. The light then passes through the sample cuvette and is reflected by a mirror to the diffraction grating. The diffraction grating disperses the light into its component wavelengths, which are recorded by the smartphone camera.
Housing: We designed the housing to be printable on any consumer or commercial 3D printer. Many libraries and schools have 3D printers available for free or minimal costs. Websites also offer 3D print services for low cost. One example is 3D Hub, which connects users to 3D printers in their area for low cost and fast turnaround times. For now, the housing is designed for the iPhone5. Other versions will be added soon. The *.stl print file is available upon request (firstname.lastname@example.org) or can be downloaded from the NIH 3D Print Exchange or Thingiverse:
Slit: The slit is a removable part of the device. The width of the opening is related to the resolution of the instrument. In our design, the slit can be removed and changed to illustrate the resolution principle. Several slits are available from 0.1 to 5 mm. The *.stl print files are available upon request (email@example.com)
Cuvette: Any 1 cm cuvette will fit in the device. Below is a link to one supplier
Mirror: A 1”x1” aluminum mirror is available from craft suppliers. It rests on a 45° face of the plastic support and is held into place with glue or double-sided tape.
Diffraction Grating: We chose an inexpensive grating that can be cut with scissors to fit the light path clearance. It is purchased as a 6”x12” film sheet with 1000 lines/mm ($2.50).
Light source: A desk lamp or LED source is fine. The only requirement is that it produces a stable light intensity and a relatively flat spectrum over the visible wavelengths.