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What is Spectral Sensitivity? Explaining Differences in Microbe Sensitivity to UV Wavelengths

Spectral Sensitivity

KLARAN UNIVERSITY / KNOWLEDGE BASE

Klaran University / Knowledge base

What is Spectral Sensitivity? Explaining Differences in Microbe Sensitivity to UV Wavelengths

As global urbanization continues to expand, creating densely populated areas, strains on water infrastructure are expected to increase 40 percent by 2030. This is leading to a rise in the incidents of waterborne illnesses in these communities. Many existing or under development water purification systems deliver hygienic water by using UVC light in the range of 200 nm to 300 nm to effectively deactivate these pathogenic microorganisms. Low pressure mercury lamps traditionally used in these systems have a single line emission at 253.7 nm. Because of the maturity of this technology, there is a plethora of research available based on microbe’s response to this exact wavelength. However, with the commercialization of UVC LEDs, an understanding of the microbe’s sensitivity to other UVC wavelengths is critical to designing effective disinfection systems.  The spectral sensitivity of a microbe is defined as the relative ability of the microbe to absorb a photon as a function of wavelength over a range of wavelengths. Figure 1 (below) shows the relative spectral sensitivity for several common pathogens referenced to a 253.7 nm low-pressure mercury lamp.

Examining these pathogens i.e. Prokaryotic (bacterial) cells E. Coli and MRSA, Eukaryotic cells (Protozoan) like “Crypto” (Cryptosporidium) and a common Obligate (virus) like Rotavirus reveals that each has a unique radiation absorption “fingerprint.” In other words, they absorb photons differently at different wavelengths based on their physical biology. While different, each pathogen demonstrates a peak absorption near 265 nm and diminishes quickly above 280 nm in the UVB range. For most pathogens, there is a steep drop in sensitivity below 250 nm - for this reason, the 250 nm to 280 nm range is typically referred to as the germicidal UVC range. The principal way UVC inactivates a pathogen is the creation of Thymine dimers within the cell DNA - which has a demonstrated peak absorption of 260 nm. However, as Figure 1 shows, the observed absorption peak and height is slightly longer and different between microbes. So why are these absorption spectras slightly different across pathogens? This change is the result of cellular protein, specifically the presence of aromatic amino acids such as tryptophan and tyrosine which have a peak absorption close to 280 nm. Cells with more of or less of these proteins effectively screen the nucleic acids and shifts the action spectrum from 260 nm to a point between 260 nm to 270 nm, with 265 nm being the most commonly observed peak.

However, some pathogens, Rotavirus being one example, show a strong absorption peak at very short UVC wavelengths close to 230 nm. This is attributable to absorbance by peptide bonds which surround the RNA. Since this attribute is limited to a narrow set of pathogens most practical UV-C disinfection products focus on emitting in the germicidal UV-C range to ensure consistent disinfection across all pathogens.

Given these differences, what should an engineer do when designing UVC disinfection systems? The best approach is to understand the spectral sensitivity of your target microbe and ensure that you have adjusted your required UV dose to the wavelength that you’re using. However, this is not always feasible or plausible, especially when designing to a cocktail of target microbes. In these cases, selecting a UV source that provides significant emission in the key germicidal wavelengths from 260 nm to 270 nm ensures the most predictable disinfection performance.

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How Much Time is Required for Surface Disinfection in Your Application?

How Much Time is Required for Surface Disinfection in Your Application?

KLARAN UNIVERSITY / KNOWLEDGE BASE

How Much Time is Required for Surface Disinfection in Your Application?

One of the most common application questions we receive from customers relates to the amount of time it takes to disinfect a surface. Accordingly, this is a critical parameter for any application design. In order to find the time required, you must first understand how we calculate the UV dose that is needed to meet the application’s disinfection goals.

Step 1: Calculate DosageFor surface disinfection applications, the UV dose is the product of the irradiance and exposure time:

When it comes to systems for flowing water, requirements are determined by more complex variables. Our UVC LED requirements calculator lets you find your application needs based on such variables. Playing with the above equation, you can find that the time necessary to disinfection a surface is equal to the quotient of the dose divided by the irradiance. Therefore, when asked how much time is required for surface disinfection in your application, you must first determine how disinfection is defined (target pathogen and log reduction). This can be found in the table in this application note (please note that all the values are collected using a low-pressure mercury lamp, and therefore need to be adjusted for the LED wavelength (and tolerances)).

Step 2: Calculate Irradiance The next step is to determine the irradiance. Irradiance is defined as the power per unit area incident upon a surface at a specified distance. It is inversely proportional to the source-to-surface distance (inverse square law function). Once you know the dose requirement and calculated irradiance, it is easy to determine amount of time necessary for the given disinfection target using the above equation. For instance, let’s consider a defined disinfection level of 99 percent reduction (i.e. 2 log reduction value) of staphylococcus aureus, and a target surface area of 10 cm x 10 cm.  

Step 3: Calculate Time To determine the time required, we will determine (1) the wavelength-specific dose required, (2) the number of LEDs and relative placement/distance, and (3) minimum irradiance point on the surface. The dose required to achieve this level of disinfection is 5.4 mJ/cm2 at 254 nm, which is an equivalent dose of 5.2 mJ/cm2 at 265 nm or 6.7 mJ/cm2 at 280 nm. We use a single Klaran 35R GD LED operated at 350 mA and at beginning-of-life, aligned to the surface center and placed 6 cm from the surface.

Klaran GD UVC LED place 60mm away from a 100mm x 100mm surface area.

The minimum irradiance value measured at the corner of the surface is 0.075 mW/cm2, which is approximately 25 percent of the peak irradiance value measured at the middle of the surface. This is modeled using an optical design software called Zemax, but can be estimated for a single LED, considering a point source and using the specified optical power and viewing angle. 

With this information, we can calculate the minimum time required for the whole surface to be disinfected for a 2 log reduction value of staph. aureus:

It is important to note that this time required is not absolute. It is impacted by the inputs on dose and irradiance (which is impacted by the UVC LED power, arrangement and distance to the surface). The key point to understand is that time and irradiance are correlated. Thus, if certain parameters of a system are open (e.g. the distance between the light source and the surface, the use of more LEDs, higher drive currents) engineers can play with these variables to minimize the exposure time, or inversely increase exposure time to lower operating characteristics. If you’re designing a product with water disinfection capabilities and want to learn about the required disinfection time for your application, explore our UVC LED Requirements Calculator.

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Microbial Performance of the Klaran AKR UVC LED Reactor

Microbial Performance of the Klaran AKR UVC LED Reactor

KLARAN UNIVERSITY / KNOWLEDGE BASE

Microbial Performance of the Klaran AKR UVC LED Reactor

Summary of collected third-party microbial performance data

Providing validated microbial performance claims targeted to customer needs quickly differentiates water purifiers and appliances. Klaran works with independent labs and our customers to expand available product claims and data against a range of target organisms to best support product managers in selecting effective solutions that are precisely oriented to what their customers are seeking.

View the Complete Test Results

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LED Tailor Innova7ion Case Study

LED Tailor Innova7ion

KLARAN UNIVERSITY / KNOWLEDGE BASE

Klaran University / Knowledge base

LED Tailor Innova7ion Case Study

Based in Finland, LED Tailor Innova7ion® has more than 10 years of experience in developing and manufacturing products with visible LED light technology and UVC LED technology. Their solutions are used for very effective surface disinfection of hand-held objects and re-usable supplies and accessories.  The company’s WiSDOM DS product is built using Klaran UVC LEDs. WiSDOM DS is a file cabinet drawer with UVC LEDs built-in to disinfect electronic devices and other non-critical medical equipment, including blood pressure cuffs and stethoscopes, in between patient visits or at the end of a shift. 

The Challenge

Commonly used hospital equipment, such as stethoscopes, blood pressure cuffs, and handheld devices such as cell phones and call buttons can transmit microbes and their spores between patients and hospital surfaces. Existing hygiene protocols recommend the use of chemical wipes for defined periods of time, ranging from one to 10 minutes to adequately treat high-touch surfaces. However, most hospital-grade disinfection wipes do not work on Clostridium difficile (C. diff) and the consistency of their use is difficult to validate. Current surface disinfection methods using chemicals can be confusing and inconsistent because of the many products available. To ensure proper disinfection, the selected agent, the manner of use (immersion vs. contact) and the treatment time must be correctly and consistently applied. Electronic devices—phones, tablets and computers—present additional challenge as these strong chemicals used to combat superbugs like C. diff often result in corrosion of the materials and can damage the devices (in fact, the warranty is often voided by the first use of the chemical). 

“ The WiSDOM DS cabinet provides a 4 log disinfection of C. diff in a three-minute cycle and can provide greater than 4 log reduction of MRSA in one-minute. Customers are surprised that by using Klaran UVC LED technology we can kill microbes in less than three minutes and that short disinfection time is highly appreciated.”

The SOLUTION

The use of Klaran UVC LEDs in WiSDOM DS enables top-level hygiene with the push of a button. It provides effective and reliable surface disinfection for small to mid-size devices, such as laptops, phones, keyboards, eyewear, keys and healthcare equipment. It prevents the transmission of harmful microbes into highly sensitive areas, including hospital cancer care units, laboratories and cleanrooms.  Klaran UVC LEDs have not only proven effective against superbugs, such as C. diff and Methicillin-Resistant Staphylococcus Aureus (MRSA), but are capable of achieving significant log reduction in seconds. When integrated into equipment like the WiSDOM DS product, these compact UVC LEDs enhance and log compliance with hygiene protocols by delivering a consistent, effective germicidal dose every time. 

“Crystal IS has the optimal UVC LEDs for us. Their support has been top-notch through our entire development cycle and the level of investment they give to help customers succeed is one of the key reasons we like working with Crystal IS. Because of this, we have every confidence our engineering team is highly competent in the use of Klaran UVC LEDs, which means we can bring to market a superior and highly effective offering.”

Crystal IS Klaran UVC LEDs are compact, are environmentally friendly, and offer efficient germicidal wavelength over traditional light sources. In addition, Klaran LEDs provide: On-demand disinfection Scalable and flexible duty cycles Energy efficiency suitable for battery-powered applications Long life

Download the Case Study PDF

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“UV LED Inside” Marketing Claims: Water Disinfection vs. Water Maintenance

Water Disinfection vs. Water Maintenance

KLARAN UNIVERSITY / KNOWLEDGE BASE

“UV LED Inside” Marketing Claims: Water Disinfection vs. Water Maintenance

As the first consumer drinking water products using UVC LED start appearing on the market, manufacturers and suppliers have begun thrashing over how ultraviolet (UV) disinfection is conveyed to consumers. Above the noise of those clamoring over who owns the right to publish feature superlatives (smallest, strongest, most dependable, etc.), the variety of applications for UVC LEDs in water dispensers represents a major opportunity for product differentiation between water purifier OEMs. LEDs inherently open the door to apply disinfection just about anywhere inside of a water system. Compared to UV lamp systems, LEDs’ small size and low voltage operation make them simple additions to a wide range of consumer appliances. Today, we’re seeing the emergence of two very disparate routes of applying UV in water: water disinfection and water maintenance.

What’s the difference between water disinfection and water maintenance?

Water disinfection is the application of sufficient UV energy to water flowing to perform disinfection at a stated reduction rate of an organism. Water maintenance is the application of UV energy to standing water or wet surfaces inside of a water system to control microbe growth. Both methods, above, can yield a product with marketing claims of “UV LED Inside” but differ astoundingly on the cleanliness of the dispensed water. Water maintenance products that appeared on the market had a low power UV LED added to the tank or spigot, ensuring that at least some of the surfaces were exposed to UV. While this can serve as a valuable method to prevent surface biofilm growth, most iterations do not have sufficient optical control or UV intensity to fully prevent growth on all wet surfaces. This results in ample opportunities for biofilm growth in the system as well as dispensed water contamination. Water disinfection differs by performing a defined log reduction of a stated organism at a certain flow rate. This type of performance messaging requires an advanced level of design as compared to a single low powered LED (~2-3 mW) mounted to PCB, yet it provides a resounding improvement to the hygiene of dispensed water. Commercial teams can leverage this distinction between disinfection and maintenance to create differentiation for their products. While “UV LED Inside” sounds great, finding resonating points of “why?” when communicating with your customers is where water disinfection defines its value as a product feature. This gives product marketers the ability to engage customers through claims against high profile reference organisms like Legionella, put the specific performance claim of 99.9 percent behind it, and match a flow rate that aligns with consumers’ point-of-use and point-of-entry water purification needs. Marketers rely on design teams to confirm that these claims are true to the product’s design. Designers should pay close attention to whether performance is at the beginning or end of the reactor’s life, assure that they or their supplier can provide test data against the most valuable target organism, and that any reactor vendor has reliable control over the LED characteristics and supply chain to ensure consistent product performance for years to come. For manufacturers who wish to incorporate such claims into their products but have little to no interest in making their own reactor design, one route is to purchase an off-the-shelf reactor and subsequently integrate it into their end product. The Klaran AKR, for example, can be relied upon to provide engaging consumer marketing claims, deep performance characterization by a number of third parties, and whose supply of UVC LEDs stems from an in-house production facility.

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