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.
This paper reports a plasmon-induced photoacoustic transducer for non-invasive skin tightening using a laser diode and an ultrathin nanoplasmonic optical absorber. The nanoplasmonic absorber consists of three-dimensional Au nanoislands (Au NIs) with high optical absorption and polydimethylsiloxane (PDMS) thin film with high thermal expansion coefficient. The low-cost and compact laser diode (LD) significantly scales down the conventional photoacoustic system based on bulk solid-state lasers and excites the nanoplasmonic absorber with sufficient optical energy to generate MHz-scale ultrasound. This plasmon-induced photoacoustic transducer opens new opportunities for ultrasound in dermatology, extending its application to portable at-home skin-care device.
This paper reports a nanoplasmonic isothermal PCR assay with CRISPR/Cas for real-time SARS-CoV-2 detection. The study utilizes a microchip and a miniaturized hand-held type photothermal PCR system, which comprises a nanoplasmonic photothermal heater and microlens array camera to maintain the temperature and detect fluorescence signal from the chip. CRISPR-based fluorescence signal detection, which proceeds simultaneously with nucleic acid amplification, indicates higher sensitivity and rapid detection. The real-time nanoplasmonic isothermal PCR assay opens a new opportunity for POCT-based CRISPR assay.
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