News and Reviews (May 2017)

Autonomously Powered Microrobots

3D microdevices with programmable functionalities

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Scanning electron micrograph of an array of low-drag microrobots with programmed catalytic engine sites

(Hakan Ceylan, Metin Sitti) A microrobot, as small as the size of a single cell, containing on-board mobility and sensing capabilities could provide an unprecedented direct access to precise control in the deep and delicate body sites, such as brain, spinal cord and eye. This could eventually lead to minimally invasive medical interventions with significantly reduced tissue damage compared with tethered catheters, endoscopes and incision-based procedures.

On the way to realize this long-term goal, Professor Metin Sitti and his coworkers at the MPI for Intelligent Systems in Stuttgart (Germany) have recently developed a key fabrication strategy, which enables programmable control of local chemical properties of a light-sensitive polymer to encode active device functions. Their strategy relies on the application of a spatiotemporally well-controlled two-photon absorption reaction in subsequent steps for each chemical entity to pattern with, which was enabled by Nanoscribe’s 3D printer Photonic Professional GT. Using this, the researchers demonstrate the first example of a computer-designed, autonomously swimming microrobot. Key to their design was an inner cavity, or a micromotor, where selectively decorated platinum nanoparticles catalytically decomposed the fuel for mechanical work. Combination of the direct laser writing technology with dedicated chemical diversification potentially opens new avenues for making active devices that were not conceivable before.

Watch how the microswimmer works and follow its trajectory moving in 5% hydrogen peroxide in the following movie.

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Two-Photon Crosslinking (TPC) Microprinting: 3D chemical patterning strategy by means of two-photon crosslinking. Inner cavity surface of the microswimmer is selectively modified (here shown carboxylic acid) for desired functional group display

[1] Hakan Ceylan, Immihan Ceren Yasa, Metin Sitti. Three-dimensional chemical patterning of micromaterials for encoded functionality. Advanced Materials, 29(9), 1605072, 2017.