This paper reports a method combining laser die transfer and mist capillary self-alignment. The laser die transfer technique is employed to feed selected microchips from a thermal release tape onto a receiving substrate and mist capillary self-alignment is applied to align the microchips to the predefined receptor sites on the substrate in high-accuracy. The parameters for a low-power laser die transfer process have been investigated and experimentally optimized. The acting forces during the mist-induced capillary self-alignment process have been analyzed and the critical volume enabling capillary self-alignment has been estimated theoretically and experimentally. We have demonstrated that microchips can be transferred onto receptor sites in 300–400 ms using a low-power laser (100 mW), and chips can self-align to the corresponding receptor sites in parallel with alignment accuracy of 1.4 ± 0.8 μm. The proposed technique has great potential in high-throughput and high-accuracy assembly of micro devices. This paper is extended from an early conference paper (MARSS 2017).

Wearable electronics have showed their profound impact in military, sports, medical and other fields, but their large-scale applications are still limited due to high manufacturing costs. As an advanced micro-fabrication process, laser processing technology has the advantages of high speed, high flexibility, strong controllability, environmental protection and non-contact in preparing micro-nano structures of wearable electronics. In this paper, a 355 nm ultraviolet laser was used to pattern the copper foil pasted on the flexible substrate, and the interconnection electrodes and wires were constructed. A processing method of multi-parallel line laser cutting and high-speed laser scanning is proposed to separate and assist in peeling off excess copper foil. The process parameters are optimized. A stretchable 3 × 3 light-emitting diode (LED) array was prepared and its performance was tested. The results showed that the LED array can work normally under the conditions of folding, bending and stretching, and the stretch rate can reach more than 50%. A stretchable temperature measurement circuit that can be attached to a curved surface was further fabricated, which proves the feasibility of this process in the fabrication of small-scale flexible wearable electronic devices. Requiring no wet etching or masking process, the proposed process is an efficient, simple and low-cost method for the fabrication of stretchable circuits.

Low-frequency vibrations can be exploited to drive a series of rotation-based devices (e.g., miniaturized centrifuges and energy harvesters), but their practical applications are hindered by the low rotation speeds of vibration-to-rotation conversion mechanisms. To address this issue, we report herein a finger-snapping inspired bistable mechanism that can achieve high-speed rotation out of low-frequency vibrations (< 5 Hz). The proposed bistable mechanism consists of two sprung-cranks, a proof mass attached with a curved beam, and a pawl, in which the bistability is owed to the coupling of the potential energy of the springs with that of the deformed beam. Both theoretical simulations and experimental tests have been done to show the feasibility of the bistable mechanism. When triggered by vibrations with frequencies varying from 3.2 Hz to 4.5 Hz, the bistable mechanism can drive a rotor to rotate uni-directionally with high speeds ranging from 900 rpm to 1300 rpm. At a low vibration frequency of 3.2 Hz, around 290% increase in the rotation speed can be achieved by the bistable mechanism as compared with the corresponding linear mechanism (rack-and-pinion mechanism). The finger-snapping inspired bistable mechanism is thus a promising candidate in the tapping of ambient low-frequency vibrations as a green energy source for some mechatronic devices.