Laser-driven noncontact bubble transfer printing via a hydrogel composite stamp

Abstract

Transfer printing that enables heterogeneous integration of materials into spatially organized, functional arrangements is essential for developing unconventional electronic systems. Here, we report a laser-driven noncontact bubble transfer printing via a hydrogel composite stamp, which features a circular reservoir filled with hydrogel inside a stamp body and encapsulated by a laser absorption layer and an adhesion layer. This composite structure of stamp provides a reversible thermal controlled adhesion in a rapid manner through the liquid-gas phase transition of water in the hydrogel. The ultrasoft nature of hydrogel minimizes the influence of preload on the pick-up performance, which offers a strong interfacial adhesion under a small preload for a reliable damage-free pick-up. The strong light-matter interaction at the interface induces a liquid-gas phase transition to form a bulge on the stamp surface, which eliminates the interfacial adhesion for a successful noncontact printing. Demonstrations of noncontact transfer printing of microscale Si platelets onto various challenging nonadhesive surfaces (e.g., glass, key, wrench, steel sphere, dry petal, droplet) in two-dimensional or three-dimensional layouts illustrate the unusual capabilities for deterministic assembly to develop unconventional electronic systems such as flexible inorganic electronics, curved electronics, and micro-LED display.

Keywords: adhesion strength; hydrogel stamp; laser-driven; transfer printing.

Fig. 1.

Schematic illustration of the laser-driven noncontact bubble transfer printing process via a hydrogel composite stamp. (A) The stamp moves down close to the donor. (B) The stamp is in contact with inks by a small preload. (C) A rapid separation retrieves the inks onto the stamp. (D) The inked stamp is moved above the receiver, leaving a gap between stamp and receiver, and a laser beam is applied to induce a bulge on the stamp surface, ensuring weak adhesion to facilitate the delamination of ink from stamp. (E) The laser beam is programmably applied to realize selective printing of inks onto the receiver. (F) Without the laser beam, the stamp surface returns to a flat state for another noncontact transfer printing cycle.

Fig. 2.

Adhesion characteristics of the hydrogel composite stamp. (A) Photograph of the composite stamp with the Inset showing the side view of stamp. (Scale bar: 1 cm.) (B) A typical force-time curve for the adhesion measurement. (C) Schematic illustrations of the hydrogel composite stamp and PDMS stamp against roughed surface under a small preload. (D) Surface roughness of Si wafer. (E) Surface roughness of white paper. The adhesion strength and the adhesion ratio of stamps against Si wafer as functions of (F) preload under a retraction speed of 50 μm/s and (G) retraction speed under a preload of 3.2 kPa. (H) The adhesion strength and the adhesion ratio of stamps against white paper as functions of preload under a retraction speed of 50 μm/s. (I) The adhesion ratio of stamps against different surfaces under a preload of 4.8 kPa and a retraction speed of 50 μm/s.

Fig. 3.

Principle of laser-driven noncontact bubble transfer printing. (A) The side view snapshots of printing a Si ink (400 μm × 400 μm × 10 μm): (I) The ink is initially on the stamp. (II) The delamination of ink from stamp. (III) The ink is completely released from stamp. (IV) The stamp recovers to its initial state. (B) The geometry of finite element model. (C) Mechanism of surface bulging for adhesion elimination: (I) water surrounding the bubble experiences a liquid–gas transition and more vapor is transmitted into the bubble and (II) The pressure inside the bubble increases. (D) Schematic illustration of the multiphysics coupling in FEA. (E) The displacement distributions in the Z direction at 10, 15, and 20 ms. (F) The maximum deflection of the bulge as the function of time. (G) The deflection of the bulge as the function of the distance from the center of the model under various times. (H) The bubble pressure and (I) the interfacial crack tip ERR as functions of laser heating time under various input laser powers. (J) The delamination time as the function of the input laser power.

Fig. 4.

Demonstrations of transfer printing inks onto different receivers in 2D and 3D layouts. (A) Microscopic images illustrating the laser-driven noncontact transfer printing of Si platelets (400 μm × 400 μm × 10 μm): (I) Si platelets are fabricated on the donor substrate, (II) Si platelets are picked up by the hydrogel composite stamp, and (III) Si platelets printed onto the glass receiver. (B) Selective printing of Si platelets with three sizes onto a PDMS substrate to form (I) a four-angle star (inks size: 400 μm × 400 μm × 10 μm), (II) a five-pointed star (inks size: 300 μm × 300 μm × 10 μm), and (III) a hexagram star (inks size: 200 μm × 200 μm × 10 μm). (C) Scanning electron microscope (SEM) images of printing Si platelets (400 μm × 400 μm × 10 μm) onto the PDMS substrates to form layouts of (I) four silicon platelets capped with one platelet in the center and three silicon platelets capped with two platelets (II) on edges or (III) on corners. (D) A “Z” pattern of Si platelets printed onto a key. (E) A “P” pattern of Si platelets printed onto a frosted glass. (F) A 3 × 3 array of Si platelets printed on a hexagon wrench. (G) A Si platelet printed onto a steel sphere. (H) A triangular layout of Si platelets printed onto a glass hemisphere. (I) A 2×2 array of Si platelets printed onto a piece of dry petal. The size of Si platelet for Fig. 4 D–I is 300 μm × 300 μm × 10 μm. (J) Si platelets (400 μm × 400 μm × 10 μm) printed onto a dimethylsilicone oil droplet surface: (I) an oil droplet on a glass sheet, (II) a Si platelet printed onto the droplet, and (III) a 2×2 array of Si platelets printed onto the droplet.