Infrared nanosensors of pico- to micro-newton forces

TL;DR

This paper introduces Tm3+-doped avalanching nanoparticle sensors capable of remotely detecting a wide range of forces from pico- to micro-newtons using near-infrared light, with high sensitivity and adaptability for diverse applications.

Contribution

The authors develop a novel nanoscale optical force sensor that operates over a large dynamic range and can be remotely addressed using NIR light, enabling versatile force measurements in complex environments.

Findings

Sensors detect forces from pico- to micro-newtons.

Force sensitivity is characterized via atomic force microscopy and spectroscopy.

Different sensing modalities like mechanobrightening are demonstrated.

Abstract

Mechanical force is an essential feature for many physical and biological processes.1-12 Remote measurement of mechanical signals with high sensitivity and spatial resolution is needed for diverse applications, including robotics,13 biophysics,14-20 energy storage,21-24 and medicine.25-27 Nanoscale luminescent force sensors excel at measuring piconewton forces,28-32 while larger sensors have proven powerful in probing micronewton forces.33,34 However, large gaps remain in the force magnitudes that can be probed remotely from subsurface or interfacial sites, and no individual, non-invasive sensor is capable of measuring over the large dynamic range needed to understand many systems.35,36 Here, we demonstrate Tm3+-doped avalanching nanoparticle37 force sensors that can be addressed remotely by deeply penetrating near-infrared (NIR) light and can detect piconewton to micronewton forces with a dynamic range spanning more than four orders of magnitude. Using atomic force microscopy coupled with single-nanoparticle optical spectroscopy, we characterize the mechanical sensitivity of the photon avalanching process and reveal its exceptional force responsiveness. By manipulating the Tm3+ concentrations and energy transfer within the nanosensors, we demonstrate different optical force-sensing modalities, including mechanobrightening and mechanochromism. The adaptability of these nanoscale optical force sensors, along with their multiscale sensing capability, enable operation in the dynamic and versatile environments present in real-world, complex structures spanning biological organisms to nanoelectromechanical systems (NEMS).