Mrs. Susanne-Marie Breme-Kirsch
,
ZeMA - Center for Mechatronics and Automation Technology, Saarbrücken, Saarland, Germany
Mr. Carmelo Pirritano
,
ZeMA - Center for Mechatronics and Automation Technology, Saarbrücken, Saarland, Germany
Ms. Kerstin Wickert
,
Applied Mechanics, Saarbrücken, Germany
Dr. Michael Roland
,
Applied Mechanics, Saarbrücken, Germany
Prof. Stefan Diebels
,
Applied Mechanics, Saarbrücken, Germany
Prof. Bergita Ganse
,
Lehrstuhl für innovative Implantatentwicklung, Homburg, Saarland, Germany
Prof. Stefan Seelecke
,
Saarland University, Saarbrücken, Saarland, Germany
Prof. Paul Motzki
,
ZeMA - Center for Mechatronics and Automation Technology, Smart Material Systems, Saarbrücken, Saarland, Germany, Saarland University, Department Systems Engineering, Saarbrücken, Saarland, Germany
Nickel-titanium shape memory alloys (SMAs) contract at specific temperatures using a reversible phase transformation between martensite and austenite. These alloys are widely used in medical devices like stents and guidewires due to their superelasticity and biocompatibility. Their adaptable design, lightweight structure, high energy density, and low cost also drive growing use as actuators in industry, aerospace, and automotive fields. Micro-wire bundles as small as 25
μm now enable continuous actuation up to 200 Hz. Additionally, by monitoring electrical resistance, SMAs can self-sense their phase, contraction, and applied force.
Recent research demonstrates that implants with adjustable stiffness and tailored stimulation patterns can improve bone fracture healing. The initial implant system used aluminum and SMA actuators for switchable rigidity. In the soft state, an additional SMA actuator set precisely stimulates the fracture site.
The prototype now features a miniaturized control unit (CU) with integrated battery, inductive charging, and a user interface (UI). The CU, ready for animal trials, supports rapid data collection, map-based control, and neural networks for fall risk assessment. The UI enables control via a Bluetooth LE WebApp.
This work introduces a new actuation design offering continuously variable stroke and stiffness. The new implant demonstrator, unlike earlier versions, provides a media-tight, load-bearing surface without external moving parts. Initial load test results with the implant fixed to a bone using standardized fixed-angle screws are presented.
