T-Box - Temperature-controlled measuring platform for automated analysis of sample sets using transmission spectroscopy

Abstract

Temperature-controlled measuring platform for the automated investigation of sample sets by means of transmission spectroscopy, characterized in that several samples are stored in a heatable sample chamber and can be measured successively with the aid of an adjustable sample wheel or sample magazine (7).

Description

1. Technical field of the invention and prior art

[0001] The temperature-controlled sample box (T-box) can be used in the field of materials analysis. It is designed to simplify the successive examination of multiple samples at a predetermined temperature using transmission spectroscopy.

[0002] For sample fixation and positioning, custom-designed sample holders and transfer stages are typically used. In addition, commercially available sample holders exist for fixing "standard samples," such as cuvettes or microscope slides, as well as temperature-controlled sample stages for examining individual samples at a predetermined temperature. 2. Deficiencies of the previously known designs and technical problems

[0003] Sample chambers / holders typically allow either temperature-dependent measurement of a single sample or the analysis of multiple samples at ambient temperature—but not both. Furthermore, there are few commercially available measurement platforms compact enough for flexible integration into existing spectroscopy setups. Commercially available platforms usually require the fabrication of custom holders and adapters, or the geometry of the samples must be adapted to the holders. This can lead to complications with sensitive samples or, more generally, to measurement inaccuracies. 3D printing allows for the custom design and cost-effective production of sample holders. The construction of compact, inexpensive, and temperature-controlled sample chambers for the analysis of single samples has also been demonstrated.However, in this case, either the stepwise examination of several samples at ambient temperature or the examination of one sample at a predetermined temperature was possible - but not both.

[0004] In summary, the following requirements for the invention emerged: - Enabling successive measurements of multiple samples without removing the sample platform between measurements - Adjustable temperature in the sample chamber - Flexible integration into a typical spectroscopy setup with transmission geometry without affecting the measurement results - Robust, automated measurement of samples over extended periods - cost-effective - Possibility of adaptation to the sample geometry 3. Problem solving

[0005] The developed sample chamber allows for the fixation of multiple samples in a sample wheel / magazine, which can then be analyzed spectroscopically in transmission. The maximum number of samples depends on their geometry and size. A sample wheel / magazine adjustable via a stepper motor enables the sequential analysis of the samples. The temperature in the sample chamber can be set from ambient temperature up to a maximum of 45 °C using a PID temperature controller, two measuring probes, a microcontroller, and two heating resistors. An external control unit, five mounting options, and three measurement slots allow for flexible integration into existing setups. The housing and the sample wheel were manufactured from PETG (polyethylene terephthalate glycol) using FDM (fused deposition modeling) 3D printing.The latter can be adapted to new sample geometries easily and cost-effectively.

[0006] The key innovation is the ability to analyze multiple samples stepwise at a predefined temperature without having to expand the platform for sample exchange. Furthermore, automation enables the analysis of samples over extended periods, allowing, for example, the monitoring of transformation processes across entire sample sets.

[0007] The prototype was designed for biplanar tablets with a diameter of 13 mm and a thickness of approximately 1 mm. The sample wheel can be adapted and manufactured for different sample geometries. If required, the design can be modified with additional mounting options and measurement slots to suit a specific spectroscopy system and then 3D printed. 4. Explanation of the invention and embodiments

[0008] Error! Reference source not found. The temperature-controlled sample box and the sample wheel / magazine were initially designed using a CAD program and subsequently manufactured using FDM 3D printing. This allows for rapid prototype iterations and later adaptations, e.g., to new sample geometries. PETG was chosen as the printing filament due to its higher temperature resistance (glass transition temperature: 80-85 °C). Regarding the sample types used (bi-planar tablets, approximately 13 mm in diameter and 1 mm thick), up to 20 samples can be fixed in the magazine. Flexible TPU plugs (thermoplastic polyurethane, Mohs hardness 85 A) are used to fix the sensitive samples in the sample slots. The magazine is reinforced at the attachment point to the axis of rotation by an aluminum insert and can be moved for sample positioning via a stepper motor.The T-Box can operate in ambient temperatures up to 45 °C. This is achieved through a PID temperature controller (Proportional-Integral-Derivative controller), two sensors, a microcontroller, and two heating elements. An active radial fan and aluminum plates ensure homogeneous heat distribution. Furthermore, an insulating layer is applied to the outside of the T-Box for improved temperature stability and reduced energy consumption. The maximum internal temperature of the T-Box can be further increased by installing additional heating elements, improving thermal insulation, and using more heat-resistant materials.

[0009] The control unit was housed in a separate enclosure to allow the T-Box to be installed even in confined spaces. This unit was also initially designed using CAD software and then manufactured using FDM 3D printing. Since this component is not exposed to elevated temperatures, bio-PLA was used as the filament. The motor, heating element, and sensor cables each have their own dedicated cable harnesses to prevent interference. All components have different interfaces to prevent incorrect connections. The control unit also features a display that shows the target temperature, the measured temperature of the two sensors, and whether the box is currently being actively heated via the resistors. The display's backlight can be switched off for light-sensitive setups. Heating and temperature information is also output every second via a serial interface.The motor control is independent of this. A sample can be selected and measured directly via the measurement software using an interface (mini-USB port) with the measuring computer.

[0010] The prototype was designed for biplanar tablets with a diameter of 13 mm and a thickness of approximately 1 mm. The sample wheel can be adapted and manufactured for different sample geometries. If required, the design can be modified with additional mounting options and measurement slots to suit a specific spectroscopy system and then 3D printed.

[0011] The invention has already been tested for the examination of pharmaceutical tablets using terahertz spectroscopy. The T-Box was easily integrated into an existing, typical setup with a transmission geometry. With careful positioning, comparative air measurements with and without the T-Box showed no influence on the measurement results. The heating behavior and temperature stability over 24 hours were tested for 30, 35, and 40 °C. The T-Box heats up to the desired temperature in less than 10 minutes for all three target temperatures and then maintains this temperature stably within a range of + / - 1.5 °C. In addition, the temperature distribution within the sample chamber at 35 °C was monitored using a thermal imaging camera.A largely homogeneous heat distribution of less than + / -2 °C can be observed at the sample sites (due to the accuracy of the thermal imaging camera used). The invention has already been used for continuous measurements of several sample sets at different temperatures (total investigation duration: up to 7 days per sample set). 5. Advantages of the invention

[0012] The main advantages are the ability to successively measure multiple samples at a predefined temperature and the flexible integration options into existing spectroscopy setups. Furthermore, the material costs for constructing a single unit amount to approximately €250. The T-Box is therefore significantly less expensive than commercially available temperature-controlled sample stages or transfer platforms. The invention fulfills the requirements specified in section 1.2, which also summarize the key advantages of the T-Box. Reference symbol list 1 Heating and temperature control elements 2. Heat-conducting plate 3 convection fans 4 attachment points 5 temperature / climate sensors 6 Actuator 7 Sample magazine 8 measuring openings with 9 plugs for closing the measuring openings 10 USB ports, temperature control 11 USB ports Stepper motor controller 12 Control panel 13. Switching off the LCD backlight 14" LCD Display

Claims

[1] Temperature-controlled measuring platform for automated examination of sample sets using transmission spectroscopy characterized by , that several samples are stored in a heated sample chamber and can be successively measured using an adjustable sample wheel or sample magazine (7). [2] Measuring platform according to claim 1 characterized by , that the samples are fixed in a sample wheel (7), which in turn can be installed in a heated sample chamber and positioned by means of a servo motor (6). [3] Measuring platform according to one of the preceding claims characterized by , that the installation of the sample chamber in measurement setups can be flexibly implemented through several fastening options (4). [4] Measuring platform according to one of the preceding claims characterized by , that the variable examination of the samples in the sample chamber is possible through several measuring openings (8), which in turn can be closed with plugs (9). [5] Measuring platform according to one of the preceding claims characterized by , that the measuring computer, the actuator (6) and the heating elements (1) with temperature sensors (5) are connected via separate cable strands and via different interface types (10) & (11) to avoid incorrect connection. [6] Measuring platform according to one of the preceding claims characterized by , that the convection fan (3) and the heat-conducting plate (2) minimize the temperature gradients in the measuring platform. [7] Measuring platform according to one of the preceding claims characterized by , that the control unit is housed in a separate enclosure and the target temperature, the measured temperature of the probes and the heating status are displayed on a display (14). [8] Measuring platform according to one of the preceding claims characterized by, that the target temperature can be set by pressing buttons built into the control unit in the control panel (12) to increase and decrease the temperature. [9] Measuring platform according to one of the preceding claims characterized by , that the backlight of the display can be turned on and off by pressing the backlight switch (13).

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