Biophotonics is largely involved in medicine/healthcare from diagnosis to healthcare through the prescription of drugs or the application of surgical and other types of treatments.
Photonics for diagnosis: Optics has enabled the development of rigid and flexible viewing endoscopes that allow minimally invasive diagnosis and treatment of numerous sites inside the body, such as the colon, the knee, the oesophagus and the uterus. Another method to investigate the “digestive system” is by letting patients swallow a tiny camera taking many pictures on its way from ingestion to exit. When analysing outer parts of the body, loupes and microscopes are also used. Optical sensors can be used to measure e.g. oxygen or sugar concentrations in the blood or other biomaterials. The market for a minimally invasive measurement of blood sugar to avoid finger sticking would be huge, since diabetes is developing epidemically.
Photonics for surgical treatment: Many different types of lasers are commonly used for surgery. A proper choice of laser wavelength and pulse duration is necessary to target specific tissue sites. The Er:YAG laser is e.g. unique in its ability to cut bone with very reduced thermal damage. Lasers can also be used for treatment of skin cancers by using light-activated drugs (photodynamic therapy). The eye is probably the part of our body where lasers have been most widely used for cutting, drilling holes, reshaping cornea surfaces etc. One can also mention that lasers can be used to solder living tissues by providing the exact required amount of heat at exactly the right place for gluing cells together. Laser systems used in medicine have been traditionally very large. Visible diode lasers, diode-pumped solid-state lasers, light-emitting diodes, and compact optical parametric oscillators are now frequently used to build new and more compact systems. Lasers together with optical fibres can be brought inside the body for surgery. One specific example is the destruction of kidney stones by lasers (laser lithotripsy).
Pharmaceutical research and the development of new drugs are strongly linked to biomedical research. So, many photonic tools described under Medical technologies are relevant to pharmaceutics. Nevertheless, for the development of drugs three tools are particularly worth mentioning:
- Micro-arrays and the excitation/detection of fluorescence to systematically and with high speed analyse the reactivity of new substances.
- Laser flow cytometry for the identification and selection of a certain type of cells to be used to investigate their sensitivity to particular substances.
- Laser tweezers for the manipulation of cells (e.g. collected using cytometry)
Agriculture and Food
Optical and photonic technologies have found many applications in agriculture, from soil and crop analysis to deciding the most opportune time for watering or harvesting via plant growth with special lighting and automatic cow milking etc. Let us describe a few of these applications in more details:
- Soil health analysis: soil health is often indicated by soil bulk density. Low bulk densities indicate more organic matter and therefore more nutrient-rich soils. Using 3D-laser scanning, one can determine the volume of grains of soil and together with their weight determine their density. Soil health is also sometimes analysed through multi-spectral imaging from airplanes.
- Crop analysis: Maybe the oldest optical technique used to analyse crop quality is the grape wine refractometer used to measure the concentration of sugar in the juice of grapes. Optical spectroscopy is used in many different ways, e.g. to measure the nitrogen level in leaves or grains or to identify levels of bruising in fruits and vegetables.
- Controlling watering: Lasers and telescopes are used in optical farming to detect evapotranspiration and help farmers decide when to irrigate. The system is based on computer-controlled analysis of the scintillation induced by the evapotranspiration.
- Plant growth stimulation through smart lighting: Efficient lighting can help controlling plant growth and quality. It is apparently possible to reduce the energy consumption by as much as 50% and at the same time produce healthier plants by controlling spectrum, intensity and timing.
- Automatic cow milking and milk analysis: Imaging or even simpler systems based on lasers and detectors can be used to control the automatic milking of cows ensuring the proper flow of the cows along the milking chain. At the same time, optical spectroscopy can be used to on-line measure the quality of the milk.