Using a 3D printer, the nanocellulose ink is applied to a carrier plate. Silver...
Using a 3D printer, the nanocellulose "ink" is applied to a carrier plate. Silver particles provide the electrical conductivity of the material.
Source: Empa

Nanocellulose sensors: wood on our skin

Researchers have now produced a novel flexible sensor that lies on the skin surface and is biocompatible because it is made of nanocellulose.

The idea of measuring parameters that are relevant for our health via the skin has already taken hold in medical diagnostics. Diabetics, for example, can painlessly determine their blood sugar level with a sensor instead of having to prick their fingers. Empa researchers, together with scientists from Canada, have now produced a novel flexible sensor that lies on the skin surface and is biocompatible because it is made of nanocellulose.

A transparent foil made of wood

Photo

Nanocellulose is an inexpensive, renewable raw material, which can be obtained in form of crystals and fibers, for example from wood. However, the original appearance of a tree no longer has anything to do with the gelatinous substance, which can consist of cellulose nanocrystals and cellulose nanofibers. Other sources of the material are bacteria, algae or residues from agricultural production. Thus, nanocellulose is not only relatively easy and sustainable to obtain. Its mechanical properties also make the “super pudding” an interesting product. For instance, new composite materials based on nanocellulose can be developed that could be used as surface coatings, transparent packaging films or even to produce everyday objects like beverage bottles.

Researchers at Empa’s Cellulose & Wood Materials lab and Woo Soo Kim from the Simon Fraser University in Burnaby, Canada, are also focusing on another feature of nanocellulose: biocompatibility. Since the material is obtained from natural resources, it is particularly suitable for biomedical research.

With the aim of producing biocompatible sensors that can measure important metabolic values, the researchers used nanocellulose as an “ink” in 3D printing processes. To make the sensors electrically conductive, the ink was mixed with silver nanowires. The researchers determined the exact ratio of nanocellulose and silver threads so that a three-dimensional network could form.

Researcher Gilberto Siqueira demonstrates the newly printed nanocellulose...
Researcher Gilberto Siqueira demonstrates the newly printed nanocellulose circuit. After a subsequent drying, the material can be further processed.
Source: Empa

Just like spaghetti – only a wee bit smaller

It turned out that cellulose nanofibers are better suited than cellulose nanocrystals to produce a cross-linked matrix with the tiny silver wires. “Cellulose nanofibers are flexible similar to cooked spaghetti, but with a diameter of only about 20 nanometers and a length of just a few micrometers,” explains Empa researcher Gilberto Siqueira.

The team finally succeeded in developing sensors that measure medically relevant metabolic parameters such as the concentration of calcium, potassium and ammonium ions. The electrochemical skin sensor sends its results wirelessly to a computer for further data processing. The tiny biochemistry lab on the skin is only half a millimeter thin.

While the tiny biochemistry lab on the skin – which is only half a millimeter thin – is capable of determining ion concentrations specifically and reliably, the researchers are already working on an updated version. “In the future, we want to replace the silver particles with another conductive material, for example on the basis of carbon compounds,” Siqueira explains. This would make the medical nanocellulose sensor not only biocompatible, but also completely biodegradable.

Subscribe to our newsletter

Related articles

Microneedles: Nano-sized, huge impact

Microneedles: Nano-sized, huge impact

By downscaling needles tool to micrometer-size, researchers open even more areas of application for them, while bypassing some of the most important issues.

3D printed sensor invented for wearables

3D printed sensor invented for wearables

Researchers have utilized 3D printing and nanotechnology to create a durable, flexible sensor for wearable devices to monitor everything from vital signs to athletic performance.

A 3D printed multifunctional pressure sensor

A 3D printed multifunctional pressure sensor

The 3D printed pressure sensor embedded with a temperature sensor is low-cost and scalable to large-scale production of smart robotic systems.

Medical technologies that come out of the printer

Medical technologies that come out of the printer

Fraunhofer-Gesellschaft's German-Polish High-Performance Center brings additive manufacturing to medical technology – first demonstrators will already be presented by the end of 2021.

Diabetes: insoles to assess the risk of foot ulcers

Diabetes: insoles to assess the risk of foot ulcers

Researchers have developed a new low-cost method to help prevent life-threatening foot ulcers in diabetic patients

3D printing in-cell protein crystals

3D printing in-cell protein crystals

In-cell nano-3D printer: Scientists have developed a promising approach for synthesizing protein assemblies from protein crystals.

Designing soft and sensitive robotic fingers

Designing soft and sensitive robotic fingers

Scientists have designed a 3D printable soft robotic finger containing a built-in sensor with adjustable stiffness.

3D printed micro-scale fluid channels

3D printed micro-scale fluid channels

Researchers have 3D printed unique fluid channels at the micron scale that could automate production of diagnostics, sensors, and assays used for a variety of medical tests and other applications.

3D printed transparent fibers can sense breath

3D printed transparent fibers can sense breath

Researchers used 3D printing techniques to make electronic fibres, each 100 times thinner than a human hair, creating sensors beyond the capabilities of conventional film-based devices.

Popular articles

Subscribe to Newsletter