Researchers at the University of Chicago developed a unique silicon device that would ease human-machine contact. By approaching 3D lithography in a novel way, team leader Bozhi Tian and his associates achieved the construction of bonelike structures that can be easily attached to the skin, while at the same time playing the role of a semiconductor.
The challenges
Biomimetics is an increasingly expanding research field which aims to improve the functionality of electronic devices by making them more adaptable to a natural environment, and mainly to aid human (and animal) patients suffering from a variety of motor conditions who can rely on such devices. One challenge facing the implementation of bio-interfaces is that the rigid materials are difficult to implant into soft, natural ones. Furthermore, prosthetic devices should be highly sensitive to both the environment as well as to the patient’s intent of movement. Tian’s laboratory approached these issues by devising a silicon mechanism by chemical means only, which resemble the reaction-diffusion processes that lead to natural symmetry-breaking shapes such as bonelike structures.
The innovation
Three-dimensional etching is a technique used to create shapes over flat surfaces and semiconductors are built using this method. Normally, wet chemical etching is used by which thin films are applied to the silicon wafers which limits the process to take place only on open surfaces. But Tian and his team found that the etching will not occur if the silicon matrix is sparsely covered with gold atoms. This technique known as “pressure modulation synthesis” uses the catalyst properties of gold upon silicon growth, by varying the sample pressure and controlling the chemical reactions of gold along the silicon surfaces. This led to both the stimulation of silicon nanowire growth and induction of gold-based patterns resembling bonelike structures.
The advantages
Pressure modulation synthesis is entirely chemical process which diminishes the role of human error in the construction of technological devices. “The idea of utilizing deposition-diffusion cycles can be applied to synthesizing more complex 3D semiconductors,” said Yuanwen Jiang, one of the authors of the study. Furthermore, such silicon spicules showed both more adherence and resistance to collagen fibres found in biological tissue. These strands were able to easily penetrate and root into the collagen, in a symbiosis similar to that of skin and bonelike structures. Details of this technique and the silicon device were published in the Science journal.
