Two-photon Absorption Polymerization Research Articles

3D micro fractal pipettes for capillary based robotic liquid handling.

Miniaturized and mobile liquid handling devices are essential elements to biological or clinical applications. This will innovate the conventional liquid handling methods such as manual or automated pipetting systems. Here, we propose the micro fractal pipette as the candidate device for this objective. It is made of epoxy polymer and printed by innovative 3D nanoprinting technology based on two-photon absorption polymerization with sub-micrometer resolution. We demonstrated the efficient liquid handling performance by using the micro fractal pipette between the source droplet and the target hydrogel substrate. This is due to the high porosity (78%) and the 8.5 times larger cavity surface area compared to the full pyramid. The biomimetic inner cavity microchannel networks contribute to the low pressure drop. The proposed micro fractal pipette could also innovate the versatile and miniaturized liquid handling system, promising to various biological or clinical applications.

Constructing multifunctional wave plates with stereo-metastructure arrays.

Driven by the development of nanophotonics and integrated optics, manipulating polarization of light with metastructures has been extensively studied in recent decades. So far there is still a high demand for more efficient ways to control the polarization state of light with extraordinary performance. In this Letter, we report on constructing multifunctional wave plates with stereo-metastructure arrays (SMAs) by two-photon absorption polymerization. In one frequency range, the SMA can turn the polarization direction of incident linearly polarized (LP) light to its orthogonal direction, acting as a half-wave plate (HWP). In the other frequency range, it converts the LP incident light to circularly polarized (CP) light, acting as a quarter-wave plate (QWP). Such a multifunctional element is expected to possess an energy efficiency as high as 75%. By encoding SMAs with different rotation angles at different spatial areas, we show that SMAs can be applied in imaging and sensing, where the focal-plane-array (FPA) imaging demonstrates patterned contrast following different structural distribution.

Femtosecond Laser in Polymeric Materials: Microfabrication of Doped Structures and Micromachining

The use of laser light to modify the material's surface or bulk as well as to induce changes in the volume through a chemical reaction has received great attention in the last few years, due to the possibility of tailoring the material's properties aiming at technological applications. Here, we report on recent progress of microstructuring and microfabrication in polymeric materials by using femtosecond lasers. In the first part, we describe how polymeric materials' micromachining, either on the surface or bulk, can be employed to change their optical and chemical properties promising for fabricating waveguides, resonators, and self-cleaning surfaces. In the second part, we discuss how two-photon absorption polymerization can be used to fabricate active microstructures by doping the basic resin with molecules presenting biological and optical properties of interest. Such microstructures can be used to fabricate devices with applications in optics, such as microLED, waveguides, and also in medicine, such as scaffolds for tissue growth.

Three-dimensional fabrication of optically active microstructures containing an electroluminescent polymer

Microfabrication via two-photon absorption polymerization is a technique to design complex microstructures in a simple and fast way. The applications of such structures range from mechanics to photonics to biology, depending on the dopant material and its specific properties. In this paper, we use two-photon absorption polymerization to fabricate optically active microstructures containing the conductive and luminescent polymer poly(2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV). We verify that MEH-PPV retains its optical activity and is distributed throughout the microstructure after fabrication. The microstructures retain the emission characteristics of MEH-PPV and allow waveguiding of locally excited fluorescence when fabricated on top of low refractive index substrates.

Reversible birefringence in microstructures fabricated by two-photon absorption polymerization

This paper reports the fabrication of birefringent microstructures using two-photon absorption polymerization. The birefringence is caused by a light-driven molecular orientation of azoaromatic molecules (Disperse Red 13) upon excitation with an Ar+ laser at 514.5nm. For an azoaromatic dye content of 1% by weight, we obtain a birefringence of 5×10−5. This birefringence can be completely erased by overwriting the test spot with circularly polarized laser light or by heating the sample. Our results open the door to the development of alternative applications in optical data storage, waveguiding, and optical circuitry.