Sound can levitate objects of different sizes and materials through air, water and tissue. This allows us to manipulate cells, liquids, compounds or living things without touching or contaminating them. However, acoustic levitation has required the targets to be enclosed with acoustic elements or had limited manoeuvrability. Here we optimize the phases used to drive an ultrasonic phased array and show that acoustic levitation can be employed to translate, rotate and manipulate particles using even a single-sided emitter. Furthermore, we introduce the holographic acoustic elements framework that permits the rapid generation of traps and provides a bridge between optical and acoustical trapping. Acoustic structures shaped as tweezers, twisters or bottles emerge as the optimum mechanisms for tractor beams or containerless transportation. Single-beam levitation could manipulate particles inside our body for applications in targeted drug delivery or acoustically controlled micro-machines that do not interfere with magnetic resonance imaging.

In typical dynamic mode operation of atomic force microscopes, steady state signals like amplitude and phase are used for detection and imaging of material. In these methods, the resolution and bandwidth are dictated by the quality factor $\mathrm{(Q)}$ of the cantilever. In this letter, we present a methodology that exploits the deflection signal during the transient of the cantilever motion. The principle overcomes the fundamental limitations on the trade off between resolution and bandwidth present in existing methods and makes it independent of the quality factor. Experimental results provided corroborate the theoretical development.

We present JOLED, a mid-air display for interactive physical visualization using Janus objects as physical voxels. The Janus objects have special surfaces that have two or more asymmetric physical properties at different areas. In JOLED, they are levitated in mid-air and controllably rotated to reveal their different physical properties. We made voxels by coating the hemispheres of expanded polystyrene beads with different materials, and applied a thin patch of titanium dioxide to induce electrostatic charge on them. Transparent indium tin oxide electrodes are used around the levitation volume to create a tailored electric field to control the orientation of the voxels. We propose a novel method to control the angular position of individual voxels in a grid using electrostatic rotation and their 3D position using acoustic levitation. We present a display in which voxels can be flipped independently, and two mid-air physical games with a voxel as the playable character that moves in 3D across other physical structures and rotates to reflect its status in the games. We demonstrate a voxel update speed of 37.8 ms/flip, which is video-rate.

We present TableHop, a tabletop display that provides controlled self-actuated deformation and vibro-tactile feedback to an elastic fabric surface while retaining the ability for high-resolution visual projection. The surface is made of a highly stretchable pure spandex fabric that is electrostatically actuated using electrodes mounted on its top or underside. It uses transparent indium tin oxide electrodes and high-voltage modulation to create controlled surface deformations. Our setup actuates pixels and creates deformations in the fabric up to +/- 5 mm. Since the electrodes are transparent, the fabric surface functions as a diffuser for rear-projected visual images, and avoid occlusion by users or actuators. Users can touch and interact with the fabric to experience expressive interactions as with any fabric based shape-changing interface. By using frequency modulation in the high-voltage circuit, it can also create localized tactile sensations on the user's fingertip when touching the surface. We provide simulation and experimental results for the shape of the deformation and frequency of the vibration of the surface. These results can be used to build prototypes of different sizes and form-factors. We present a working prototype of TableHop that has 30x40 cm2 surface area and uses a grid of 3x3 transparent electrodes. It uses a maximum of 9.46 mW and can create tactile vibrations of up to 20 Hz. TableHop can be scaled to make large interactive surfaces and integrated with other objects and devices. TableHop will improve user interaction experience on 2.5D deformable displays.