Researchers create stretchable, skin-conformable microscale surface-emitting laser

From personal diagnostics to therapeutics, wearable and implantable electronics have a wide range of potential applications. However, the development for certain components has been hampered by challenges such as the rigid and brittle nature of semiconductor wafers used in optoelectronic sensors.

A new article reports on a stretchable, microscale surface-emitting laser capable of being conformally integrated on the soft, curvilinear surfaces of biological tissues. The lasers provide wafer-level performance under a mechanical and thermal environment relevant to skin physiology and, to the authors’ knowledge, is the first demonstration of its kind.

Kang et al. employed specialized epitaxial design and a printing-based integration method that enabled the defect-free release of 850-nm gallium arsenide-based microscale vertical cavity surface emitting lasers (micro-VCSELs). They then implemented the micro-VCSELs onto an ultra-compliant elastomeric membrane with serpentine-shaped metal interconnects to make the device stretchable.

Another major challenge in the development of implantable electrically-driven lasers has been heat management. To circumvent this problem, the authors integrated a composite structure that incorporates thin metal layers as a heat-spreading medium to accelerate the heat removal from the laser cavity.

The resulting stretchable assemblies of microlasers exhibited stable continuous-wave operation under both uniaxial and biaxial tensile strains up to 120 percent. The authors were surprised to observe that the output power of the laser on human skin and air was maintained at 81 percent and 76 percent, respectively, compared to the reference case where a copper heat sink was used.

Source: “Stretchable, skin-conformal microscale surface-emitting lasers with dynamically tunable spectral and directional selectivity,” by Dongseok Kang, Huandong Chen, and Jongseung Yoon, Applied Physics Letters (2019). The article can be accessed at https://doi.org/10.1063/1.5080947 .