The device, described in the open-access journal HardwareX by Gianmauro Fontana, Nicola Iacono, Gabriele Papadia and Simone Pio Negri, is designed to manipulate surface mount technology (SMT) components with planar dimensions from 0.5 by 0.5 millimetres up to 8 by 8 millimetres, with heights between 0.3 and 5 millimetres. That range spans the vast majority of parts routinely assembled onto PCBs, from tiny passive resistors to sizeable ball grid array packages. By integrating two complementary grasping technologies into one end-effector, the gripper eliminates the frequent tool changes that erode throughput in flexible manufacturing, and it adds a third, hybrid operating mode in which both grasping mechanisms act on the same component simultaneously.

Each of the two primary modes has well-known strengths and weaknesses. Vacuum grippers, which use suction cups connected to a Venturi-effect vacuum generator, excel at delicate handling of flat, smooth components and can be miniaturised cheaply, but they apply only a single vertical force and can struggle to release micro-scale parts, where electrostatic, van der Waals and capillary adhesion forces cause components to stick to the tool. Friction grippers, by contrast, use two opposing fingers to grip parts from the sides, providing firmer, bilateral holding, yet they occupy more space, risk crushing fragile parts without force control, and suffer their own sticking effects on very small components. Hybrid designs have been explored before, combining electrostatic, electrothermal or capillary techniques, but the new tool stands out by pairing the two methods most common in industrial PCB assembly and by packaging them in a modular, largely 3D-printed body.

Mechanically, the gripper is organised around three sub-assemblies. A fixed 3D-printed base supports a central vacuum tool holding an interchangeable micro suction cup, together with a mobile frame carrying two L-shaped fingers. This mobile frame is driven vertically by a single-acting pneumatic cylinder that develops a lifting force of about 22 newtons at 6 bar, deliberately sized to resist soldering forces of between 0.05 and 0.2 newtons acting along both vertical and horizontal axes. That robustness is not incidental: the fingers themselves are printed in a high-temperature resin from Formlabs that withstands soldering temperatures up to 240 degrees Celsius, allowing the tool to hold a component firmly in place while an operator, or another robot, solders it. This makes the gripper directly usable in collaborative robotics scenarios such as operator-assisted soldering, a capability few commercial alternatives offer.

Horizontal positioning of the fingers is handled by two low-cost miniature linear stages, each actuated by a two-phase stepper motor through a gear-and-lead-screw transmission. The stages provide a 9.1-millimetre stroke with a full linear step of 25 micrometres, and each can sustain the horizontal and vertical reaction forces of roughly 0.2 newtons that the fingers impose during grasping. The designers paid careful attention to tolerances in the pneumatic cylinder, specifying an H7/h6 mobile coupling that balances accurate positioning against low friction; a small deliberate leak even produces a mild air bearing between piston rod and cylinder. In the friction mode, with a closing force of 0.2 newtons per finger and an assumed polymer–metal friction coefficient of 0.5, the tool can hold components weighing up to about 0.2 newtons, while the suction cup adds a further, configurable contribution that scales with cup diameter, reaching nearly 0.6 newtons at 1 millimetre.

The control system is built around an Arduino Due microcontroller running an Atmel SAM3X8E ARM Cortex-M3 processor at 84 megahertz, paired with an Ethernet shield for TCP/IP communication with a supervisory PC. Two STSPIN220 stepper drivers command the finger stages, while MM10 linear potentiometers provide position feedback with an effective resolution of 2.68 micrometres through the microcontroller’s 12-bit analogue-to-digital converter. A second-order IIR low-pass filter with a 50-hertz cutoff suppresses sensor noise, cutting the standard deviation of position measurements by 87 percent to just 2 micrometres in the worst case. Solenoid valves and opto-isolated relays handle the two-state control of vacuum and the pneumatic cylinder, and an external EEPROM preserves configuration parameters through power failures. MATLAB scripts sit on top of this embedded layer purely as a supervisory and analysis tool, used for data logging, system identification and PID tuning rather than for real-time control.

The tuning workflow itself is a small masterclass in applied control engineering. The researchers first eliminated mechanical backlash with an open-loop warm-up movement, then measured the true linear step size using a Mitutoyo digital indicator with a 0.001-millimetre resolution. Stroke calibration and sensor sensitivity estimation were automated inside the firmware. Eight open-loop motion cycles per finger axis, with speeds from 3 to 24 millimetres per second and durations from 0.4 to 3 seconds sampled at 0.5 milliseconds, fed a first-order system identification in MATLAB; validation on held-back cycles achieved at least 96 percent fit accuracy. PI controllers, tuned for maximum robustness with anti-windup and speed feedforward compensation, then track trapezoidal motion profiles generated online by the firmware’s multi-threaded, pseudo-real-time scheduler, which separates actuation control, communication and manual-or-automatic mode management into independent loops.

Experimental validation put these numbers to the test. Thirty grasp-and-release cycles were run for each component and each grasping mode, using a ball grid array package measuring 8 by 6 by 0.8 millimetres and a 1005 resistor measuring just 1 by 0.5 millimetre. Friction and vacuum grasping achieved a perfect 100 percent pick-and-release reliability for both parts, and the hybrid mode matched that figure for the BGA component. Closed-loop tracking kept finger positioning errors within the 50-micrometre control tolerance, with the two fingers synchronised to within 30 milliseconds of each other. A stall-detection strategy, triggered when commanded displacement exceeds the estimated mechanical backlash, let the fingers stop independently upon contact with grasped parts or with neighbouring components on the board, protecting both the motors and the delicate electronics. Disturbance-rejection tests confirmed that the controllers recover their setpoints smoothly after unexpected external forces are applied and removed.

The tests also exposed an honest limitation. On the 1-millimetre resistor, the hybrid mode failed because of mechanical interference between the fingers and the suction cup, a problem the authors attribute to the current finger geometry rather than to the concept itself, noting that revised finger shapes could overcome it. They also map out the trade-offs clearly: friction grasping suits firm, accurate manipulation but needs more clearance, vacuum excels with delicate parts but holds them with only a single force, and the hybrid approach delivers the best holding stability and release precision, with the fingers’ upward motion acting as an integrated plug-like release mechanism against micro-scale adhesion, yet it is not yet ready for sub-millimetre components.

Even with those caveats, the economics are striking. The complete bill of materials comes to 562.66 euros, including upper-bound estimates for small hardware, printed parts and machined metal components, with an optional 750-euro automatic tool changer that can be replaced by a simple fixed interface. Most parts are additively manufactured, only a few require CNC machining, and every CAD file, schematic, firmware routine and MATLAB script is released under a Creative Commons Attribution 4.0 licence through a public repository. For research labs, small manufacturers and anyone building flexible robotic assembly cells, that combination of verified performance, multi-mode versatility and full open-source reproducibility makes the hybrid micro-gripper a genuinely compelling piece of hardware, and a signal of where low-cost, reconfigurable micromanipulation is heading.

Subject of Research: Design and experimental validation of a multi-mode hybrid vacuum-friction micro-gripper for robotic manipulation and assembly of surface mount technology components

Article Title: Multi-mode hybrid micro-gripper for micro-manipulation and micro-assembly

Article References: Fontana, G., Iacono, N., Papadia, G., & Negri, S. P. (2026). Multi-mode hybrid micro-gripper for micro-manipulation and micro-assembly. HardwareX, Article e00850. https://doi.org/10.1016/j.ohx.2026.e00850

Image Credits: AI Generated

DOI: 10.1016/j.ohx.2026.e00850

Keywords: micro-gripper, robotics, PCB assembly, surface mount technology, vacuum grasping, friction grasping, micro-manipulation, closed-loop control, open source hardware, additive manufacturing, Arduino Due, micro-assembly