SignificanceUltrasonic transducers facilitate noninvasive biomedical imaging and therapeutic applications. Optoacoustic generation using nanoplasmonic structures provides a technical solution for highly efficient broadband ultrasonic transducer. However, bulky and high-cost nanosecond lasers as conventional excitation sources hinder a compact configuration of transducer.AimHere, we report a plasmon-enhanced optoacoustic transducer (PEAT) for broadband ultrasound generation, featuring an overdriven pulsed laser diode (LD) and an Ecoflex thin film. The PEAT module consists of an LD, a collimating lens, a focusing lens, and an Ecoflex-coated 3D nanoplasmonic substrate (NPS).ApproachThe LD is overdriven above its nominal current and precisely modulated to achieve nanosecond pulsed beam with high optical peak power. The focused laser beam is injected on the NPS with high-density electromagnetic hotspots, which allows for the efficient plasmonic photothermal effect. The thermal expansion of Ecoflex finally generates broadband ultrasound.ResultsThe overdriven pulsed LD achieves a maximum optical peak power of 40 W, exceeding the average optical power of 3 W. The 22 μm thick Ecoflex-coated NPS exhibits an eightfold optoacoustic enhancement with a fractional −6 dB bandwidth higher than 160% and a peak frequency of 2.5 MHz. In addition, the optoacoustic amplitude is precisely controlled by the optical peak power or the laser pulse width. The PEAT-integrated microfluidic chip clearly demonstrates acoustic atomization by generating aerosol droplets at the air–liquid interface.ConclusionsPlasmon-enhanced optoacoustic generation using PEAT can provide an approach for compact and on-demand biomedical applications, such as ultrasound imaging and lab-on-a-chip technologies.
Given with the success of OLEDs in many consumer electronics, the search for scalable, additive patterning technique for organic thin films is still continued because the established fabrication method for OLEDs relies on thermal evaporation assisted with fine-metal mask technique, with a low material utilization efficiency and a limited scalability for sequential patterning of RGB subpixels. This talk will introduce recent efforts made for organic vapor-printing (OVJP combining the additive, scalable nature of inkjet printing and the solvent-free advantages of thermal evaporation, to work better with flexible electronics and to allow for batch definition of multiple pixels for display applications.
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