The prototype thermoelectric assembly for medical and biological applications
Nowadays, the most authentic method for diagnosing coronavirus infection of SARS-CoV-2 (COVID-19) the polymerase chain reaction (PCR) method considered.
PCR is a molecular biology method that allows to find the genetic material of the virus in biological material (in the patient's blood, saliva, or any other biological fluid). During PCR take place of significant amplification of quantity of certain fragments of nucleic acid (DNA or RNA) for visual detection afterward. The PCR method is wide use in medicine, veterinary medicine, food industry, genetics and forensics.
The technical department of Crystal Ltd. has developed a prototype of the thermoelectric assembly TA-DA-48-27-0/100 for laboratory research equipment. This assembly from Direct-to-Air family.
The amplification of DNA fragment proceeds in the mode of rapid change of the sample temperature. Depending on the study, the number of heating and cooling cycles is set in the device. This thermoelectric assembly quickly changes from heating mode to cooling mode because has a low thermal inertia.
In this thermoelectric assembly heating and cooling cycles are proceed by using a high-performance compact heat pump - Peltier module with production of Crystal Ltd. The thermoelectric modules for this assemblies was produced on aluminum nitride substrates. AlN has a higher thermal conductivity than Al2O3 ceramics and increase the cooling or heating rate.
The temperature of the samples is measured by a sensor, which is installed in the body of the cooled/heated plate. Type of sensors available for installation: PT100; PT500; PT1000; 50M. To control the modules in the temperature maintenance mode, it is possible to operations in the PID control mode. PWM frequency is at least 5 kHz recommended.
Thermoelectric assembly TA-DA-48-27-0/100 is designed for operating voltage in the range from 22 VDC to 27 VDC. The startup/nominal current at a voltage of 24 VDC is 14 A / 10.7 A. For supply voltage of 27 V and ambient temperature of +25 °C, the heating and cooling rate is 1.5 °C/sec. approximately. The operating temperature range is from 0 ºС to +100 ºС. The overall dimensions are 270x153x115 mm, weight is of 3.8 kg. The sound pressure level is 46 dB (A) (at a distance of 1 m).
Disposable plastic tubes with a volume of 0.6 ml are used as reaction vessels. The number of places for test tubes on the contact heat exchanger is 48 pieces.
One of the features this design of thermoelectric assembly is that the seat on the plate maximally copies profile of the test tube for the best heat contact.
The contact heat exchanger is made of aluminum alloy. Anodized surface provides reliable anticorrosion protection.
This prototype thermoelectric assembly be used as one of the main components of the compact thermal cycler.
The next development will a prototype of a thermoelectric assembly that will has of two separated contact heat exchangers.
This prototype will be implemented the concept of the two contact heat exchangers and the ability for each of operation by separate management program.
To contact heat exchangers can be manufactured fixation molds for test tubes required volume of 0.2-0.6 ml. The number of wells can be increased to 96 pcs, depending on the volume of the tubes.
Thermal and mechanical Engineer at Crystal Ltd.
Aleksandr Saunin
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