Advances in High-Speed, Multiparametric Atomic Force Microscopy

After decades of technological advancements, high-speed atomic force microscopy (HS-AFM) has emerged as a powerful technique for visualizing dynamic processes. At the nanoscale, the AFM provides valuable insights into the sample by sensing minute interaction forces with the surface. The temporal resolution of the microscope is limited by its slowest component, necessitating constant refinements. In this work, we tackle some of the bottlenecks in instrumentation and propose two HS-AFM systems, to cover a broad spectrum of applications ranging from the study of the dynamic behavior of purified proteins to the characterization of larger samples such as cells, polymers, or inorganic materials. We address the challenges associated with the inherent trade-off between scan range and temporal resolution and report a HS-AFM with an extended range. The instrument is compatible with ultra-short cantilevers and enables direct cantilever actuation through photothermal drive. To simultaneously achieve a broad scan range and high-speed capability, a dual-actuation scheme is employed. We showcase the capabilities of the HS-AFM by imaging polymer blends with micro-phase separation, achieving a surface velocity of up to 10 millimeters per second.

Extending the range of HS-AFM presents numerous challenges, one of which is in regard to driving fast nanopositioners incorporating large stack piezoelectric actuators (PEA). The response time of piezo drivers constitutes one of the speed bottlenecks in HS-AFM. We present a high-voltage amplifier comprised of a separate amplification and a novel voltage-follower power stage. This amplifier effectively drives the large capacitive loads of PEA stacks, introducing minimal phase delay in the feedback loop. We demonstrate the amplifier's merit by imaging tubulin protofilament dynamics at a sub-second frame rate.

In the current academic research landscape, improving the overall performance of HS-AFM has become increasingly challenging. Developers often face the dilemma of either having to modify proprietary technology from commercial AFM manufacturers or invest significant resources in re-engineering instruments. These hurdles significantly hinder the progress and resource allocation in the field. To overcome these challenges and re-empower academic development, we present a research-grade, open-source HS-AFM platform. We showcase its capabilities by capturing bio-molecular processes at a speed of up to ten frames per second. The platform proves valuable for visualizing the assembly of blunt-end short-arm DNA three-point stars and the kinetics of the centriolar scaffolding SAS-6 protein.

We explore the synergy of combining microscopy techniques to unveil new measurement possibilities and present the first integration of an atomic force microscope (AFM) with a helium ion microscope (HIM). These two techniques provide complementary information about the sample and are suitable for imaging electrical insulating samples. Moreove