arXiv subjects

Max Linnander

Publications and source records attributed to Max Linnander.

5 recordsLinked to original sources

arXiv2026

Wave Focusing in Metamaterials: Tactile Displays Beyond the Diffraction Limit

We address the challenge of engineering distributed haptic displays capable of reproducing multiple localized, independently addressable vibrations -- representing virtual tactile pixels -- at arbitrary locations on a surface. Our technique is based on the focusing of mechanical waves in a flexural plate using a sparse set of actuators. At tactile frequencies, wave diffraction prevents the formation of localized virtual tactile pixels at spatial scales relevant for multi-digit touch interactions. We overcome this limitation by augmenting the plate with a lattice of mechanical resonators, forming a locally resonant metamaterial plate. Coupling between the plate's dynamic modes and those of the resonators alters the dispersion relation governing wave transmission, introducing a slow-wave branch that enables focusing beyond the diffraction limit imposed by the unmodified plate. We use numerical simulations to engineer the dispersion relation of the metamaterial system for high-resolution focusing at tactile frequencies. We then fabricate a metamaterial tactile display and experimentally demonstrate virtual pixels that are far more localized than those generated on an otherwise identical plate without resonators, resulting in a tenfold reduction in virtual-pixel area. In behavioral experiments, we show that this system can deliver perceptually localized single- and multi-point tactile feedback and moving tactile sources while maintaining independent control over temporal waveforms at multiple display locations. The methods reported here can enable high-resolution haptic displays for widespread applications using a small number of actuated degrees of freedom.

cs.ET↗

arXiv2026

Thermopneumatic Pixels: Fast, Localized, Robust, Low-Voltage Touch Feedback

We present thermopneumatic pixels (TPPs) -- low-profile pixels and arrays that generate dynamic tactile feedback. These devices are thin, fast, reconfigurable, and output localized transient displacements at each pixel. Their parsimonious design -- a layered architecture without internal moving parts -- and low-voltage ($\lesssim$10 V) operation may facilitate practical integration in a wide variety of interfaces. Each TPP converts brief electrical pulses into transient air pressure increases in an internal cavity, yielding out-of-plane forces and displacements for tactile feedback. We demonstrate TPPs that output displacements of 1 mm and forces exceeding 1 N, with millisecond response times, in packages that are less than 3 mm thick. Force and displacement increase with pixel surface area, facilitating tailorability. The pixels can also generate oscillating feedback at pulse rates up to 300 Hz range. We report designs for compact arrays of pixels at 4 mm spacing, and simple pulse driving architectures using miniature transistors driven by microcontrollers. We characterize the mechanical, dynamic, and thermal response of TPPs, and their robustness and consistency over tens of thousands of cycles. We report perceptual experiments on spatial localization and intensity as a function of driving power. Together, these results establish thermopneumatic pixels as a compact, adaptable tactile technology that blends performance and practicality.

cs.HC↗

arXiv2026

Haptic Light-Emitting Diodes: Miniature, Luminous Tactile Actuators

We present Haptic Light-Emitting Diodes (HLEDs), luminous thermopneumatic actuators that directly convert pulsed light into mechanical forces and displacements. Each device packages a miniature surface-mount LED in a gas-filled cavity that contains a low-inertia graphite photoabsorber. The cavity is sealed by an elastic membrane, which functions as a working diaphragm. Brief optical pulses heat the photoabsorber, which heats the gas. The resulting rapid pressure increases generate forces and displacements at the working diaphragm. Millimeter-scale HLEDs produce forces exceeding 0.4 N and displacements of 0.9 mm at low voltages, with 5 to 100 ms response times, making them attractive as actuators providing tactile feedback in human-machine interfaces. Unusually, these actuators are also light-emitting, as a fraction of optical energy is transmitted through the membrane. These photomechanical actuators have many potential applications in tactile displays, human interface engineering, wearable computing, and other areas.

cs.HC↗

arXiv2024

Tactile Displays Driven by Projected Light

Tactile displays that lend tangible form to digital content could transform computing interactions. However, achieving the resolution, speed, and dynamic range needed for perceptual fidelity remains challenging. We present a tactile display that directly converts projected light into visible tactile patterns via a photomechanical surface populated with millimeter-scale optotactile pixels. The pixels transduce incident light into mechanical displacements through photostimulated thermal gas expansion, yielding millimeter scale displacements with response times of 2 to 100 milliseconds. Employing projected light for power transmission and addressing renders these displays highly scalable. We demonstrate optically driven displays with up to 1,511 addressable pixels -- several times more pixels than any prior tactile display attaining comparable performance. Perceptual studies confirm that these displays can reproduce diverse spatiotemporal tactile patterns with high fidelity. This research establishes a foundation for practical, versatile high-resolution tactile displays driven by light.

cs.ET↗

arXiv2022

A peristaltic soft, wearable robot for compression and massage therapy

Soft robotics is attractive for wearable applications that require conformal interactions with the human body. Soft wearable robotic garments hold promise for supplying dynamic compression or massage therapies, such as are applied for disorders affecting lymphatic and blood circulation. In this paper, we present a wearable robot capable of supplying dynamic compression and massage therapy via peristaltic motion of finger-sized soft, fluidic actuators. We show that this peristaltic wearable robot can supply dynamic compression pressures exceeding 22 kPa at frequencies of 14 Hz or more, meeting requirements for compression and massage therapy. A large variety of software-programmable compression wave patterns can be generated by varying frequency, amplitude, phase delay, and duration parameters. We first demonstrate the utility of this peristaltic wearable robot for compression therapy, showing fluid transport in a laboratory model of the upper limb. We theoretically and empirically identify driving regimes that optimize fluid transport. We second demonstrate the utility of this garment for dynamic massage therapy. These findings show the potential of such a wearable robot for the treatment of several health disorders associated with lymphatic and blood circulation, such as lymphedema and blood clots.

cs.RO↗