Black silicon sensors for molecular contamination

Cages for cells on black Si. Mechanical stimulation/stress induced on cells can be tracked in time as cells are confined in the cages

July 2013

Black silicon provides a unique platform for a non-reflecting, all-direction-absorbing surface, which can be used for sensing and fingerprinting of molecular and microbial contamination. This is done by sensing the light scattered in air, water, food, body fluids by various compounds.

Detection of dyes from a family of carcenogenic compounds was made using black silicon. Nano-textured surfaces of black silicon are suitable as practical, cheap, single-use substrates for efficient measurements in water, food or medical fields. Their sensitivity of detection is superior to the commercial Klarite substrates currently used in industry.

A team of MCN engineers and Swinburne PhD students led by Professor Saulius Juodkazis perfected efficient, large-area fabrication of black silicon using plasma processing, after which they carried our different characterisation tests. These showed that black silicon substrates can be used as substrates for laser fabrication, sensors for light scattering and detection of tiny numbers of molecules. Black silicon is highly absorbant of light rays, with only 1% of light reflected from its surface, as opposed to the usual 35% of reflected light on other materials.

The most interesting outcome of this project is the demonstration that black silicon can be used as a sensing substrate. This was not initially obvious as the low reflectivity makes it a challenge to detect light scattered from black silicon. The group showed that this is not an issue for reaching high sensitivity performance. This is significant as a few millimetres of commercially available Klarite sensors cost more than a few inches of black silicon.

Single use sensors are must in the medical, food, water and air control industries. Black silicon can become a platform to develop such sensors using new, label-free and established surface functionalisation technologies.

The group plans to fabricate die-chips of black silicon for sensing and make them ready to use after coating with gold film. Black silicon substrates are promising for bio-physics research with the possibility for strongly influencing cell membrane functions with nano-needles of black silicon.