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From electronic devices to large-area electronics, from individual cells to skin substitutes, printing techniques are providing compelling applications in wide-ranging fields. Research has thus fueled the vision of a hybrid, printing platform to fabricate sensors/electronics and living engineered tissues simultaneously. Following this interest, we have fabricated interdigitated-electrode sensors (IDEs) by inkjet printing to monitor epithelial cell cultures. We have fabricated IDEs using flexible substrates with silver nanoparticles as a conductive element and SU-8 as the passivation layer. Our sensors are cytocompatible, have a topography that simulates microgrooves of 300 &micro, m width and ~4 &micro, m depth, and can be reused for cellular studies without detrimental in the electrical performance. To test the inkjet-printed sensors and demonstrate their potential use for monitoring laboratory-growth skin tissues, we have developed a real-time system and monitored label-free proliferation, migration, and detachment of keratinocytes by impedance spectroscopy. We have found that variations in the impedance correlate linearly to cell densities initially seeded and that the main component influencing the total impedance is the isolated effect of the cell membranes. Results obtained show that impedance can track cellular migration over the surface of the sensors, exhibiting a linear relationship with the standard method of image processing. Our results provide a useful approach for non-destructive in-situ monitoring of processes related to both in vitro epidermal models and wound healing with low-cost ink-jetted sensors. This type of flexible sensor as well as the impedance method are promising for the envisioned hybrid technology of 3D-bioprinted smart skin substitutes with built-in electronics.

The number of elderly and care dependent persons is continuously increasing. The percentage of people over 60 years rises worldwide from 10% in 2000 to 21 % of the world's population in 2050. [1] The usage of wearable sensors in combination with telemedicine have a big potential to ensure a continuous healthcare and nursing of chronically ill and old patients and to enable them an independent life into old age. [2] The development and assembly of a modular low-power multi-sensor platform with wireless data transmission allows to set up a specific sensor network depending on location and application on the body. The wearable electronics consisting of a gyroscope, temperature and pressure sensors and low-power microcontroller with Bluetooth transmitter are integrated into a shoe insole and encapsulated in silicone as a first prototype. This smart sensor insole measures the vital and body data to monitor the patient's physical activity. Advanced sensor analysis enables to detect a fall of the wearer, which can be triggered to call for help from nurses or relatives. In a further development an energy harvesting version including a rechargeable microbattery and battery management system leads the way to an energy-autarkic operation and maintenance-free telemedical patients monitoring for homecare and ambient assisted living of our aging and digitalized society.

Novel approaches in cell based and cell free micro reactors promise a new generation of high quality, high purity and on top personalized synthesis of drugs like antibiotics and functional proteins. These concepts are - however-relying on very specific conditions, under which the cells need to work and therefore require advanced sensing for e.g. ionic content, pH value and temperature. Also, the creation of product itself needs to be monitored to extract the valuable drug from the reactor, before side reactions start to deteriorate quality and yield. Microfluidics has come a long way since, resulting in advanced Point of Care devices nowadays, which can run complex protocols/1/. However, these reactions are time based and the process conditions are fixed and not monitored at all. To leverage the capability to drug production, monitoring sensors need to be integrated into the fluidic system, creating a complex electronic-optical microfluidic device. Exemplary techniques for the integration of sensors are provided in this paper, technological approaches and experimental results are given.