Embedding sensors into orthopedic devices can enable these implants to monitor the progress of the healing process or detect cues of complications. The simple structure of inductor–capacitor (LC) resonance sensors combined with their wireless readout offers a desirable basis for such sensors. A set of eight bioresorbable inductively coupled pressure sensors is fabricated. The conductors are formed by e‐beam evaporation of magnesium (7 µm) directly onto the substrates, after which two substrates are adhered to a holed spacer to form an LC sensor. All the sensors show a fairly linear pressure response in the physiological pressure range from 0 to 200 mm Hg with an average pressure sensitivity of −6.0 ± 0.5 kHz mm Hg−1. After the pressure response tests, the effects of known error sources are determined. Finally, the sensor performance in vitro in buffer solution at +37 °C is evaluated. The sensors function tolerably for the first 8 h in immersion, after which they are disabled by mechanical changes in the sensor structure. To conclude, a bioresorbable battery‐free wireless pressure sensor architecture with an adequate sensitivity for biomedical applications is described. However, further studies are required to improve the stability of the sensors under physiological conditions.

Bioresorbable passive resonance sensors based on inductor–capacitor (LC) circuits provide an auspicious sensing technology for temporary battery-free implant applications due to their simplicity, wireless readout, and the ability to be eventually metabolized by the body. In this study, the fabrication and performance of various LC circuit-based sensors are investigated to provide a comprehensive view on different material options and fabrication methods. The study is divided into sections that address different sensor constituents, including bioresorbable polymer and bioactive glass substrates, dissolvable metallic conductors, and atomic layer deposited (ALD) water barrier films on polymeric substrates. The manufactured devices included a polymer-based pressure sensor that remained pressure responsive for 10 days in aqueous conditions, the first wirelessly readable bioactive glass-based resonance sensor for monitoring the complex permittivity of its surroundings, and a solenoidal coil-based compression sensor built onto a polymeric bone fixation screw. The findings together with the envisioned orthopedic applications provide a reference point for future studies related to bioresorbable passive resonance sensors.

Cite this article: Palmroth A, Pitkänen S, Hannula M, Paakinaho K, Hyttinen J, Miettinen S, Kellomäki M. 2020 Evaluation of scaffold microstructure and comparison of cell seeding methods using micro-computed tomographybased tools.Micro-computed tomography (micro-CT) provides a means to analyse and model three-dimensional (3D) tissue engineering scaffolds. This study proposes a set of micro-CT-based tools firstly for evaluating the microstructure of scaffolds and secondly for comparing different cell seeding methods. The pore size, porosity and pore interconnectivity of supercritical CO 2 processed poly(L-lactide-co-ε-caprolactone) (PLCL) and PLCL/β-tricalcium phosphate scaffolds were analysed using computational micro-CT models. The models were supplemented with an experimental method, where iron-labelled microspheres were seeded into the scaffolds and micro-CT imaged to assess their infiltration into the scaffolds. After examining the scaffold architecture, human adipose-derived stem cells (hASCs) were seeded into the scaffolds using five different cell seeding methods. Cell viability, number and 3D distribution were evaluated. The distribution of the cells was analysed using micro-CT by labelling the hASCs with ultrasmall paramagnetic iron oxide nanoparticles. Among the tested seeding methods, a forced fluid flow-based technique resulted in an enhanced cell infiltration throughout the scaffolds compared with static seeding. The current study provides an excellent set of tools for the development of scaffolds and for the design of 3D cell culture experiments.royalsocietypublishing.org/journal/rsif J. R. Soc. Interface 17: 20200102

The emergence of transient electronics has created the need for bioresorbable conductive wires for signal and energy transfer. We present a fully bioresorbable wire design where the conductivity is provided by only a few micrometers thick electron-beam evaporated magnesium layer on the surface of a polymer fiber. The structure is electrically insulated with an extrusion coated polymer sheath, which simultaneously serves as a water barrier for the dissolvable magnesium conductor. The resistance of the wires was approximately 1 Ω cm–1 and their functional lifetime in buffer solution was more than 1 week. These properties could be modified by using different conductor materials and film thicknesses. Furthermore, the flexibility of the wires enabled the fabrication of planar radio frequency (RF) coils, which were wirelessly measured. Such coils have the potential to be used as wireless sensors. The wire design provides a basis for bioresorbable wires in applications where only a minimal amount of metal is desired, for example, to avoid toxicity.