Thermal Management of High-Performance Bioelectronics using Effective Assembly of Inorganic Nanosheets
김태일 교수
성균관대학교

As flexible and deformable electronics dramatically advance, their components should be fabricated for miniaturized scale, and integrated on limited-size substrates with extremely high density. Current technologies for 1) the integration and interconnection of electronics as well as 2) preventing thermal degradation in deformable electronics show some critical limitations in the application of microscale electronics. It is noted that highly integrated assembly usually has inevitable concern on assembling accuracy which requires critical alignment and thermal degradation due to limited heat releasing property of flexible and stretchable substrate. To address these problems, herein, a new direct and vertical interconnection driven by selective dewetting of a polymer adhesive is introduced for question #1. The interconnection system consists of the polymer adhesive and nanosized metal particles, or structured electrodes. Nanoscale-dewetting windows formed by controlling the stability and wetting property of the adhesive polymer are controlled by the interfacial property of the coated polymer adhesive. The adhesive is coated on substrate by a simple spin-coating process, and its ultraviolet curable property allows only the device-mounted parts to be selectively conductive and sticky, while the other parts form insulation and protection layers. The interconnection of the electronics and substrate by adhesive makes it possible to apply the technique to various microsize electronics with electrode size and pitch of 20 μm or less, and endure dramatic temperature change and a long-term high humidity environment. Moreover, over display comprising over 10 000 microscale light-emitting diodes (micro-LEDs), and commercialized microchips are demonstrated with monolithic integration on flexible and transparent substrate. Presented here for question #2, moreover, is an effective assembly technique to realize a continuous array of boron nitride (BN) nanosheets on tetrahedral structures, creating 3D thermal paths for anisotropic dissipation integrated with deformable micro LEDs. The tetrahedral structures, with a fancy wavy shaped cross-section, guarantee flexibility and stretchability, without the degradation of thermal conductivity during the deformation of the composite film. The structured BN layer in the composites induces a high thermal conductivity of 1.15 W m-1 K-1 in the through-plane and 11.05 W m-1 K-1 in the in-plane direction at the low BN fraction of 16 wt%, which represent 145% and 83% increases over the randomly mixing method, respectively. Furthermore, this structured BN composite maintains thermal dissipation property with 50% strain of the original length of composite. Also, various electronic device demonstrations provide exceptional heat dissipation capabilities, including thin film silicon transistor on flexible and stretchable composite, respectively.