Ali Javey and co-workers, UC Berkeley, USA, have developed a pressure-sensitive electronic material made out of inorganic single crystalline semiconductors. They grew germanium/silicon nanowires on a cylindrical drum, which was then rolled onto a polyimide film. This formed a thin, flexible sheet and a matrix of pixels. Each pixel contained a transistor made up of semiconductor nanowires integrated with pressure sensitive rubber. The matrix required less than 5 V of power to operate, could detect pressure from 0 to 15 kPa and maintained its robustness after more than 2,000 bending cycles.

Zhenan Bao and colleagues, Stanford University, USA, used of a thin film of polydimethylsiloxane molded into a grid of pyramids to form a sensor with high sensitivities and fast response to stimuli. The film was capable of storing charge and could be sandwiched between electrodes. The amount of charge the film can store depends upon the amount of compression acting on it. The film is less than 1 mm thick, flexible and able to detect objects of as little as 20 mg.

Touch-sensitive artificial skin would help overcome key challenges in robotics and prosthetics: adapting the amount of force needed to hold and manipulate objects.

• Nanowire active-matrix circuitry for low-voltage macroscale artificial skin
  K. Takei, T. Takahashi, J. C. Ho, H. Ko, A. G. Gillies, P. W. Leu, R. S. Fearing, A. Javey,
  Nat. Mat. 2010, 9.
  DOI: 10.1038/nmat2835
• Highly sensitive flexible pressure sensors with microstructured rubber dielectric layers
  S. C. B. Mannsfeld, B. C-K. Tee, R. M. Stoltenberg, C. V. H-H. Chen, S. Barman et al.,
  Nat. Mat. 2010, 9.
  DOI: 10.1038/nmat2834