As the wearables market grows, so too does the emergence of patches. Patches for virtually everything — from glucose monitoring to pipeline monitoring — are proving their might in the wearables market.

Largely unobtrusive, patches have grown in number and uses. Follow along with GlobalSpec to see just how varied their applications have become.

Wound care

An electrically charged, thin-film patch designed to expedite wound healing has been developed by a team from the University of Electronic Science and Technology of China.

The thin film patch, which relies on electricity to expedite wound healing, is comprised of four layers: the top and bottom layers feature electrically charged plastic that receives a charge via contact with the wearer’s skin; one middle layer of silicone rubber gel that enables the patch to conform to the contours of the wearer’s skin; and the other middle layer that features a shape memory alloy material that pulls the sides of the wound together.

In the lab, the researchers applied the 0.2 mm thick film to both circular and straight-line wounds on rats, determining that the film demonstrated significantly faster wound healing when compared to results achieved using other wound dressings or no dressings at all.

Source: University of Electronic Science and Technology of China

Ultrasound

Researchers from the University of California San Diego (UC San Diego) have developed a tiny patch that performs ultrasounds.

Developers suggest that the elastic, adhesive patch can measure tissue stiffness up to 4 cm underneath the skin with a reported spatial resolution of 0.5 mm.

To create the patch, the UC San Diego team “integrated an array of ultrasound elements into a soft elastomer matrix and used wavy serpentine stretchable electrodes to connect these elements,” producing a patch that can reportedly perform ultrasounds and remote medical monitoring.

Further, the patch is comprised of a 16 x 16 array of transducer elements connected together by a seven layer electrode and enveloped by a waterproof and biocompatible silicone elastomer. Meanwhile a backing layer composed of silver epoxy absorbs vibrations, thereby expanding bandwidth and improving resolution. Additionally, the patch captures 3D images underlying tissue.

Source: UC San Diego

Vaccines

Scientists from Stanford University and the University of North Carolina at Chapel Hill have developed a 3D-printed patch for delivering the COVID-19 vaccine painlessly.

Source: University of North Carolina at Chapel Hill

The 3D-printed polymer patch, which features an array of microneedles, delivered an immune response 10 times that of vaccines delivered via syringe in the lab, according to the researchers. There, the patch produced a T-cell and antigen-specific antibody response 50 times greater than that administered via subcutaneous injection.

Speaking

Researchers at Beijing’s Tsinghua University have designed a thin adhesive patch that amplifies the voice of its wearer.

The voice amplification patch, which is roughly 25 mm thick, interprets and projects barely voiced and even silently mouthed words when adhered to the outside of a wearer’s throat.

The graphene-based intelligent, wearable artificial throat (AT) adheres to the skin above a wearer’s larynx via standard medical adhesive, while a series of tiny wires connect the patch to a small microcontroller powered by a coin-sized battery.

Once adhered, the patch monitors for minute throat vibrations that are then interpreted by an AI model. On the heels of this AI analysis, artificial sound is projected through the patch itself, emitting up to 60 decibels via electrical input thanks to the device battery that allows for the sound waves via temperature changes.

Tattoos

Users can tattoo themselves without the pain or blood associated with standard tattoos thanks to a tattoo patch developed by researchers from the Georgia Institute of Technology (Georgia Tech).

Source: Georgia Tech

The patch features microneedles smaller than grains of sand that encase tattoo ink in a dissolvable matrix and deposits the ink into the skin via the microneedles. This approach, according to the researchers, only affects a superficial layer of skin versus the standard tattoo process, which uses a mechanized needle to puncture skin and inject ink into the second layer of skin.

Because the patch only delivers ink to the superficial layer of skin, the microneedles avoid both blood vessels and nerve endings, thereby keeping the process pain- and blood-free.

Pipelines

Scientists from Osaka University, Chuo University, Eindhoven University of Technology and the National Institute of Advanced Industrial Science and Technology have developed a non-disruptive sheet sensor for monitoring the quality of liquids that flow through the pipes of chemical factories, food and beverage manufacturers, and other industrial facilities.

To develop the onsite, non-destructive quality control method for such facilities, where sampling, chemical labels or an external light source are traditionally employed to frequently check the quality of water, the scientists developed a flexible sheet that includes an embedded carbon nanotube film that functions as a photodetector layer.

Source: Osaka University

When the sheet was exposed to light radiation, the carbon nanotubes reportedly created an electric voltage that was detectable by attached electrodes.

"Our stretchable sheet device is equipped with a high-sensitivity, broadband optical sensor, which enables it to be attached to a wide variety of pipe shapes," the authors explained.

Meanwhile, water temperature changes can also be passively monitored according to blackbody radiation, which is otherwise known as the spectrum of light emitted by any heated object. Additionally, to detect impurities or inspect beverages, researchers determined that an external terahertz or infrared light source could be employed, thereby allowing spectroscopy techniques to be applied without interruption to flowing liquids.

"The optical sensor sheet can easily visualize the concentration, temperature, viscosity, and location of cracks and liquids in pipes, contributing to the realization of future environmental measurement systems," explained the authors.

Safety gear

A team of textile scientists from the University of Alberta in Canada have developed a sensor patch that detects the subtle signs of fiber breakdown — due to ultraviolet (UV) light, moisture and heat exposure — in the protective garments worn by firefighters.

Because aging protective gear is a safety hazard for firefighters and that breakdown is not always visible to the naked eye, the University of Alberta team developed a sensor patch that can be adhered to protective garments.

The sensor patch uses graphene to create conductive tracks on the patch’s surface. When exposed to heat, moisture and UV light that exceeds a certain threshold, the graphene track will lose its electrical conductivity and an accompanying voltmeter checks the sensor patch to determine if electrical conductivity has been lost — signaling that the garment is no longer safe.

Drug testing

Researchers from Chung-Ang University, Pohang University of Science and Technology, University of Science and Technology and Korea Institute of Materials Sciences (KIMS) have created a wearable sensor that immediately detects illegal drugs present in the sweat of the wearer via nanomaterial technology.

The sensor reportedly uses surface-enhanced Raman scattering technology to enhance the Raman signal of chemical substances, including narcotics, by 10¹⁰ and even more.

Source: KIMS

To develop the wearable optical sensor, researchers extracted a silk fibroin protein from a silkwood cocoon to create a 160 nm thick film, which was then coated with 250 nm thick silver nanowire and subsequently attached to a medical-grade patch.

Adhered to the skin, the patch absorbs sweat and the drug substance within the wearer’s sweat penetrates the sensor, reaching the silver nanowire. The patch is then irradiated via the Raman laser, revealing the presence of the drug.

According to the developers of the patch, this process can be done in approximately one minute — much quicker than traditional drug testing approaches such as blood and urine testing wherein biological specimens are tested in a lab setting.

Heart monitoring

Researchers from the University of Houston have developed a cardiac patch composed of rubber bioelectronics that can be used for monitoring heart health and treating heart disease.

Source: University of Hoston

The rubbery bioelectronic implantable device could potentially replace pacemakers and other cardiac devices, which are generally too rigid, making it harder to monitor a beating heart, or too soft, which limits the amount of data that can be collected by these devices.

The cardiac patch can simultaneously collect data such as electrophysical activity, temperatures, heartbeats and other signals of heart health.

This list of patches is by no means exhaustive. In fact, there are so many new applications for patches that GlobalSpec will undoubtedly continue covering this topic.