Airy-beam holographic sonogenetics for advancing neuromodulation precision and flexibility.

Advancing our understanding of brain function and developing treatments for neurological diseases hinge on the ability to modulate neuronal groups in specific brain areas without invasive techniques. Here, we introduce Airy-beam holographic sonogenetics (AhSonogenetics) as an implant-free, cell type-specific, spatially precise, and flexible neuromodulation approach in freely moving mice. AhSonogenetics utilizes wearable ultrasound devices manufactured using 3D-printed Airy-beam holographic metasurfaces. These devices are designed to manipulate neurons genetically engineered to express ultrasound-sensitive ion channels, enabling precise modulation of specific neuronal populations. By dynamically steering the focus of Airy beams through ultrasound frequency tuning, AhSonogenetics is capable of modulating neuronal populations within specific subregions of the striatum. One notable feature of AhSonogenetics is its ability to flexibly stimulate either the left or right striatum in a single mouse. This flexibility is achieved by simply switching the acoustic metasurface in the wearable ultrasound device, eliminating the need for multiple implants or interventions. AhSonogentocs also integrates seamlessly with in vivo calcium recording via fiber photometry, showcasing its compatibility with optical modalities without cross talk. Moreover, AhSonogenetics can generate double foci for bilateral stimulation and alleviate motor deficits in Parkinson's disease mice. This advancement is significant since many neurological disorders, including Parkinson's disease, involve dysfunction in multiple brain regions. By enabling precise and flexible cell type-specific neuromodulation without invasive procedures, AhSonogenetics provides a powerful tool for investigating intact neural circuits and offers promising interventions for neurological disorders.

Ring-Focusing Fresnel Acoustic Lens for Long Depth-of-Focus Focused Ultrasound with Multiple Trapping Zones.

This paper describes a novel acoustic transducer with dual functionality based on 1-mm-thick lead zirconate titanate (PZT) substrate with a modified air-cavity Fresnel acoustic lens on top. Designed to let ultrasound waves focus over an annular ring region, the lens generates a long depth-of-focus Bessel-like focal beam and multiple trapping zones based on quasi-Airy beams and bottle beams. With 2.32 MHz sinusoidal driving signal at 150 Vpp, the transducer produces a focal zone with 9.9 mm depth-of-focus and 0.8 MPa peak pressure at a focal length of 31.33 mm. With 2.32 MHz continuous sinusoidal drive at 30-35 Vpp, the transducer is able to trap multiple polyethylene microspheres (350-1,000 µm in diameter and 1.025-1.130 g/cm3 in density) in water either simultaneously (when suspended by mechanical agitation or released from water surface) or sequentially (when placed one after another with a pipette). The largest particles the transducer could trap are two 1-mm-diameter microspheres stuck together (1.07 mg in weight, lifted by buoyance and 0.257 µN acoustic-field-induced force). When the transducer is moved laterally, some firmly trapped microspheres follow along the transducer's movement, while being trapped. When trapped, some microspheres can rotate due to the rotation torque generated by the quasi-Airy beams.

Plasmonic Metalens to Generate an Airy Beam.

Airy beams represent an important type of non-diffracting beams-they are the only non-diffracting wave in one dimension, and thus they can be produced with a cylindrical geometry that modifies a wavefront in one dimension. In this paper, we show the design of a cylindrical plasmonic metalens consisting of an array of nanoslits in a gold thin layer that modulates the phase of a Gaussian beam to generate an airy beam propagating in free space. Based on the numerical results, we show that it is possible to generate an airy beam by only matching the phase of wavefronts coming out from the array of gold nanoslits to the airy beam phase at plane z=0. We numerically demonstrate that the airy beam exhibits bending over propagation and self-healing properties. The transmission efficiency is around 60%. The simplicity of the proposed structure open new perspectives in the design of flat metasurfaces for light-focusing applications.

Airy Beam-enabled Binary Acoustic Metasurfaces for Underwater Ultrasound Beam Manipulation.

Airy beams are peculiar beams that are non-diffracting, self-accelerating, and self-healing, and they have offered great opportunities for ultrasound beam manipulation. However, one critical barrier that limits the broad applications of Airy beams in ultrasound is the lack of simply built device to generate Airy beams in water. This work presents a family of Airy beam-enabled binary acoustic metasurfaces (AB-BAMs) to generate Airy beams for underwater ultrasound beam manipulation. AB-BAMs are designed and fabricated by 3D printing with two coding bits: a polylactic acid (which is the commonly used 3D printing material) unit acting as a bit "1" and a water unit acting as a bit "0". The distribution of the binary units on the metasurface is determined by the pattern of Airy beam. To showcase the wavefront engineering capability of the AB-BAMs, several examples of AB-BAMs are designed, 3D printed, and coupled with a planar single-element ultrasound transducer for experimental validation. We demonstrate the capability of AB-BAMs in flexibly tuning the focal region size and beam focusing in 3D space by changing the design of the AB-BAMs. The focal depth of AB-BAMs can be continuous and electronical tuned by adjusting the operating frequency of the planar transducer without replacing the AB-BAMs. The superimposing method is leveraged to enable the generation of complex acoustic fields, e.g., multi-foci and letter patterns (e.g., "W" and "U"). The more complex focal patterns are shown to be also continuously steerable by simply adjusting the operating frequency. Furthermore, the proposed 3D-printed AB-BAMs are simple to design, easy to fabricate, and low-cost to produce with the capabilities to achieve tunable focal size, flexible 3D beam focusing, arbitrary multipoint focusing, and continuous steerability, which creates unprecedented potential for ultrasound beam manipulation.

Lightsheet Microscopy.

In this paper, we review lightsheet (selective plane illumination) microscopy for mouse developmental biologists. There are different means of forming the illumination sheet, and we discuss these. We explain how we introduced the lightsheet microscope economically into our core facility and present our results on fixed and living samples. We also describe methods of clearing fixed samples for three-dimensional imaging and discuss the various means of preparing samples with particular reference to mouse cilia, adipose spheroids, and cochleae. © 2022 The Authors. Current Protocols published by Wiley Periodicals LLC.

All-Dielectric Synthetic-Phase Metasurfaces Generating Practical Airy Beams.

Accelerating optical beams exhibit exotic features, such as nondiffractive propagation, self-acceleration, and self-healing, which have led their use in a wide range of photonics applications. However, spatial light modulator-based generators of such beams suffer from narrow operational bandwidth, high cost, low diffraction efficiency, and limited integration capability. Although recent metasurface-based approaches have yielded generators with significantly improved bandwidths and integration capacities, the resultant devices usually have ultrashort working distances and limited control over characteristic beam parameters, which decreases their utility in optical imaging and manipulation applications. Herein, we describe a synthetic-phase metasurface-based approach that overcomes these problems and increases the degrees of freedom to enable effective control of beam parameters by integrating a cubic phase profile and the phase of a Fresnel holographic lens into a single metasurface. We demonstrate this approach by using the synthetic metasurface to generate a series of Airy beams with controllable focal length (i.e., working distance), narrowed beam width, and extended propagation distance. Crucially, these beam parameters are fully adjustable, which makes these focal-length-modifiable Airy beams particularly appealing for use in high-resolution, large field-of-view imaging, and deep-penetration optical manipulation. Furthermore, we show that imposing the phase of a Dammann grating into a synthetic metasurface generates a 1 × 4 array of Airy beams that exhibit the aforementioned optical properties. These findings suggest that synthetic-phase metasurfaces may significantly broaden the application of accelerating optical beams in various fields, such as light-sheet microscopy, super-resolution stochastic optical-reconstruction microscopy, laser fabrication, and parallel processing and in the development of optical tweezers for use with live samples.

Cubic-Phase Metasurface for Three-Dimensional Optical Manipulation.

The optical tweezer is one of the important techniques for contactless manipulation in biological research to control the motion of tiny objects. For three-dimensional (3D) optical manipulation, shaped light beams have been widely used. Typically, spatial light modulators are used for shaping light fields. However, they suffer from bulky size, narrow operational bandwidth, and limitations of incident polarization states. Here, a cubic-phase dielectric metasurface, composed of GaN circular nanopillars, is designed and fabricated to generate a polarization-independent vertically accelerated two-dimensional (2D) Airy beam in the visible region. The distinctive propagation characteristics of a vertically accelerated 2D Airy beam, including non-diffraction, self-acceleration, and self-healing, are experimentally demonstrated. An optical manipulation system equipped with a cubic-phase metasurface is designed to perform 3D manipulation of microscale particles. Due to the high-intensity gradients and the reciprocal propagation trajectory of Airy beams, particles can be laterally shifted and guided along the axial direction. In addition, the performance of optical trapping is quantitatively evaluated by experimentally measured trapping stiffness. Our metasurface has great potential to shape light for compact systems in the field of physics and biological applications.