An Atomic Force Microscope with Dual Actuation Capability for Biomolecular Experiments

Abstract

We report a modular atomic force microscope (AFM) design for biomolecular experiments. The AFM head uses readily available components and incorporates deflection-based optics and a piezotube-based cantilever actuator. Jetted-polymers have been used in the mechanical assembly, which allows rapid manufacturing. In addition, a FeCo-tipped electromagnet provides high-force cantilever actuation with vertical magnetic fields up to 0.55 T. Magnetic field calibration has been performed with a micro-hall sensor, which corresponds well with results from finite element magnetostatics simulations. An integrated force resolution of 1.82 and 2.98 pN, in air and in DI water, respectively was achieved in 1 kHz bandwidth with commercially available cantilevers made of Silicon Nitride. The controller and user interface are implemented on modular hardware to ensure scalability. The AFM can be operated in different modes, such as molecular pulling or force-clamp, by actuating the cantilever with the available actuators. The electromagnetic and piezoelectric actuation capabilities have been demonstrated in unbinding experiments of the biotin-streptavidin complex.

Magnetic probe-based microrheology reveals local softening and stiffening of 3D collagen matrices by fibroblasts

“…Although one electromagnet with a sub-millimeter tip can exert forces on cell-size-scale probes that are sufficient for measuring the stiffness levels of E=0.5 kPa (Sevim et al. ( 2016 )), the exerted force varies non-linearly with probe–electromagnet-tip distance, and is unidirectional, hindering measurements of dynamic viscoelasticity. The use of more than one electromagnet is required for two reasons.…”

A perspective view on the nanomotion detection of living organisms and its features

“…Chemical cross‐linkers, such as 3‐aminopropyl tryethoxysilane (APTES) or glutaraldehyde (GA) are more suitable for bacterial adhesion 30,42 . On the other hand, proteins such as poly‐ l ‐lysine, 43 poly(ethyleneimine), 44 fibronectin, 45 concanavalin A, 46,47 and collagen 48 provide a better adhesion with mammalian cells. A nonexhaustive list of the principal chemicals used as functionalizing agents for AFM biological applications are reported in Table 1.…”

“…The extremely high sensitivity of the nanomotion systems implies that the measurements are greatly susceptible to artifacts induced by liquid evaporation, temperature changes, and acoustic noise, which must be monitored throughout the entire experimental time period 45,47 . Most noise sources can be eliminated by confining the instrument to acoustic‐isolated boxes and by the use of active or passive vibration‐isolation tables.…”

Miniaturized magnetic bead-actuators for force-clamp spectroscopy-based single-molecule measurements

“…The customized AFM system consists of a 3D printed head and a sample stage which is integrated with electromagnetic manipulator system. The details of design, realization, and characterization of the system are explained in our previous work [19].…”

“…Previously, we introduced a new method of actuation using magnetic beads as miniaturized actuators for single-molecule experiments without a need for a piezoelectric actuator or a substrate [19] [20]. We use the piezoelectric actuator only for precise positioning and turn it off during data recording.…”