The highly-sensitive tests that up to now have been restricted to laboratory use are integrated into smart wearables "beyond what a FitBit or Applewatch can offer", said study co-author Peter Nguyen a research scientist at the Wyss Institute at Harvard University.

"The concept is similar to how our own skin works, where you automatically sense your environment with exquisite sensitivity without needing to actively participate in the details of the process itself," he said.

In the new study, scientists were able to re-create the cell parts that sense dangerous microorganisms and freeze-dry them.

They are then re-activated to begin testing by adding water -- like a "package of instant ramen noodles", according to Nguyen.

Such tests have previously been based on living cells, which researchers said can be too fragile and sometimes dangerous in non-medical settings.

In the new study, researchers used cell-free reactions that contain the tools of a living cell without the cell itself.

Since they are not alive, the sensors can be freeze-dried and stored for months until they are ready to be activated.

The authors showed that these sensors, which use CRISPR gene editing technology, could match laboratory virus detection and be woven into wearable fabrics.

Nguyen said the wearable detectors might be useful for "anyone working in an environment where they might be exposed to pathogens or toxins".

Researchers developed a prototype Covid-19 testing face mask with a patch of sensors attached to a pad that collects the user's breath particles.

After the wearer has used the mask for at least 15 minutes, they pierce a small pouch on the mask and water wicks the sample into the sensor for analysis.

A strip on the mask displays the result.

- Wearable warning -

The researchers also developed a jacket for a liquid "exposure event", for people working in dangerous environments.

It employs the gene-editing tool CRISPR -- which is used in medicine to target specific genetic material such as are found in viruses -- to create sensors that light up when exposed to the target pathogen.

Fibre optic threads in the jacket carry information from tiny sensors in the fabric to a miniature detector within the garment that is the size of a small candy bar.

"In the short term, we see the wearables and especially the face masks being used in the clinic for specialised situations," he added.

But Nguyen also said that in the long run the garments could be used by regular people, especially in the case of local outbreaks for easy at-home testing.

- Batteries not needed -

In another study published Monday in Nature Biotechnology, scientists at Northwestern University developed a small, flexible cardiac pacemaker that is completely absorbed by the body once it has fulfilled its use.

Heart patients with short-term needs, such as those recovering from surgery, have typically relied on pacemakers that are only partially implanted.

Power and programming has to be transmitted to the devices via tubes and wires that penetrate the skin, increasing risks of infection or wounding due to movement.

"Moreover, when pacing is no longer needed," the study notes, "removal of the implanted device carries the risk of damaging heart tissue."

The new device, which researchers tested on various animal subjects including mice and dogs, is made completely of bio-resorbable materials and can be programmed to be absorbed into the body after a specific timeframe.

It is battery free and operates via "wireless energy transfer".

The study's authors said they hoped the technology would "provide safer solutions for patients requiring post-operative temporary pacing technology".

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