Laser-driven hierarchical "gas-needles" for programmable and high-precision proximity transfer printing of microchips.

Micro-transfer printing (μTP) techniques are essential for advanced electronics. However, current contact/noncontact μTP techniques fail to simultaneously achieve high selectivity and transfer accuracy. Here, a laser projection proximity transfer (LaserPPT) technique is presented, which assembles the microchips in an approach-and-release manner, combining high-precision parallelism with individual chip control. An embedded carbon layer with a thin gas layer is generated by an ultraviolet laser, followed by absorbing heat from the infrared laser, to enable the sequential expansion of hierarchical "gas-needles." The level 1 large gas-needle with a substantially growing height can reduce the gap between the microchip and the receiver. Then, the level 2 small gas-needles enable the gentle release of a chip. Therefore, the LaserPPT can obtain a strong adhesion modulation (~1000 times), excellent size scalability (<100 micrometers), and high transfer accuracy of ~4 micrometers. Last, the assembly of a micro-light-emitting diode display demonstrates the capabilities for deterministic assembly of microarrays.