3D Printing

Forget Wearable and 3D Printed, This Is 3D Fabricated Injectable Electronics

We probably should have seen this coming: in the past we have often read about 3D printed electronics, 2D printed conductive inks on 3D printed surfaces, 3D printed embedded chips, all leading to ubiquitous concepts such as wearable electronics, the Internet of Things and smart/connected objects. However, more and more often lately, science moves faster than science fiction. We had never yet imagined something that a group of scientists from the Department of Biomedical Engineering at the School of Medicine of Tsinghua University in Beijing, found quite obvious and already demonstrated experimentally to be feasible: injectable 3D fabricated electrodes work better than wearable ones.

3d fabrication process

The way the process works is in some ways more similar to a 3Doodler than an actual 3D printer. The team of scientists, lead by the study’s corresponding author, Jin Liu, found an “alternative way of making three-dimensional (3D) medical electronics inside the biological body through sequential injections of biocompatible packaging material and liquid metal ink.” What that means is that they injected a sort of gel into the body that works as a shell, creating an isolated pocket under the skin. Then they inserted conductive liquid metal (GalnSn, a gallium alloy) into the gel and found that they could create a 3D electrode that worked both as a highly efficient ECG (Electrocardiograph) and a stimulator electrode.

Before writing this off as mad Chinese science and picturing a world of people tracked by the government (in the worst case scenario) or communicating telepathically (in the better case scenario) let us look at the most realistic applications. These are going to be medical devices. That means that the people that will use them will probably need them to save their lives by constantly monitoring their health and vital signs or even to provide immediate treatment of life endangering conditions.

Pacemakers, defibrillators, cochlear implants, drug monitoring and delivery systems are all electronic devices that contribute to the efficient management of diseases and conditions such as Parkinson’s, hearing disorders, diabetes or cardiaca arrhythmia. Many of these Implantable Medical Devices (IMD) are surgically inserted in the body of the patient (so, you see, internal electronics is nothing new) causing extreme discomfort, complicated maintenance and high costs for the patients.

in vivo experimentation

The injectable 3D fabricated systems aims to address all these concerns through the recently discovered properties and merits of liquid metal based printed and fabricated electronics: low melting temperatures for easy moulding, well controlled wettability and high electrical conductivity. Using the liquid gallium alloy, the scientists were able to create — both in vitro and in vivo (once again nothing new: live animal testing is mandatory in China) — and electrical wire network, a node shaped electronic component and a 3D triangle frame electronic component. By injecting the metal into its soft gelatin case inside the body, the scientists found that it caused no injury and virtually no discomfort to the host.

in vitro experimentation

To test the efficiency of their system Jin Liu’s team first used porcine tissue for in vitro experiments and used a 1 mm syringe needle to shape the electrode mould inside the gelatin, fabricating a GalnSn-based liquid ink electrode with the same diameter: this demonstrated that injectable electronics would be a good media for administering the desirable stimulation into the biological tissue. To test the working behaviour of the injected electrode, a live mouse and a live frog were used (with approval by the University’s Ethics Committee).

The 3D fabricated electrode was inserted into the mouse on the left side of the thorax, near the upper limb, through a wound so small it can be considered negligible. However the electrode gave extremely accurate ECG readings, far superior in accuracy to a regular ECG external sensor. The experiment on the frog was used to test the ability of the injected electrode to transmit signals to the nerves, in particular the frog’s sciatic nerve, once again with excellent results.

So are we soon going to have all sorts of sensors, accelerometers, chips and wires injected into our bodies to keep us alive (and possibly turn us into an army of evil cyborgs at the flick of a button?). Probably not anytime soon. Currently the gelatin shell does not offer sufficient guarantees for quickly shaping and maintaining an adequate isolation because of the existing solution flow within the living animal or human tissue. These issues, however, will be addressed by adding enzymes as curing agents or Alginate (a substance used in molecular cooking as well), or even by using new gel-based materials.

The complexity of the devices that will be able to be implanted will depend upon the control of the injector’s shifting and injection speed (read: 3D printers and bioprinters): currently, in fact, the electrode’s moulding is all done by controlling the syringe by hand. As advanced as the theory behind it is, this is just a beginner’s tool, to familiarize you with a technology that, conspiracy theories aside, might soon really make a lot of people’s lives better.