Post on 23-Jun-2020
A THz sensors and sensor conceptsA THz sensors and sensor conceptsProf. Dr. Hartmut RoskosTerahertz-Physik und UltrakurzzeitspektroskopiePhysikalisches Institut des Fachbereichs PhysikGoethe-Universität Frankfurt
11.04.2013 | LOEWE-Schwerpunkt "Sensors towards Terahertz" | Hartmut Roskos | 1
A1A1
Jun.-Prof. (THz-Sensoren)Chemistry and materials sciences (Schneider, Riedel)Physics (Roskos)Physics (Roskos)Microsystems (Schlaak) Electromagnetic simulations (Weiland)
11.04.2013 | LOEWE-Schwerpunkt "Sensors towards Terahertz" | Hartmut Roskos | 2
A1 GoalsA1 Goals
Exploration of various electro-magnetic sensor concepts with regard t th i it bilit f ti l li ti S ifi lto their suitability for practical applications. Specific goals:
Very high sensitivity
Integration of functional layers into the sensor structure (A3, A4)
Inclusion of sample handling capabilities (microfluidic systems) and integration of emitters and detectors to form an ultimately compactintegration of emitters and detectors to form an ultimately compact lab-on-chip system
11.04.2013 | LOEWE-Schwerpunkt "Sensors towards Terahertz" | Hartmut Roskos | 3
A1 Sensor conceptsA1 Sensor concepts
mis
sion
250 m
Metamaterials: Periodically Frequency (THz)
Tran
s
650 m
m
Metamaterials: Periodically arranged, resonant structures
Sensor waveguide
Frequency (THz)
Grating structures
Sensor
Sensor waveguide
areaReferenceSplitter Coupler
11.04.2013 | LOEWE-Schwerpunkt "Sensors towards Terahertz" | Hartmut Roskos | 4
Exploitation of substrate wavsWaveguides
A1 Cooperation routes in the pconsortium
A1 A2, A3, A4 Sensor 1Sensor 1
, ,
Sensor 2Sensor 2C2 C3Sensor 3Sensor 3
11.04.2013 | LOEWE-Schwerpunkt "Sensors towards Terahertz" | Hartmut Roskos | 5
A2A2
Cooperation Roskos/Krozer with MPI for BiophysicsMikrofluidics: Schlaak Sensor implementation jointly with Jun.-Prof. (THz sensors)
11.04.2013 | LOEWE-Schwerpunkt "Sensors towards Terahertz" | Hartmut Roskos | 6
(THz sensors)
A2 Transport mechanisms inpbiological membranes
MPIBP: Electrophysiological approaches to unravel the functional
Method: SSM-Electrophysiology (SSM:
MPIBP: Electrophysiological approaches to unravel the functional principles of membrane proteins
Cur
rent
p y gy (Solid Supported Membrane)
On Substrate Off
• Voltage-free capacitive method, measures displacement currents
• Can be automatedCan be automated• For bacteriae and intracellular
compartiments
11.04.2013 | LOEWE-Schwerpunkt "Sensors towards Terahertz" | Hartmut Roskos | 7
A2 GoalsA2 Goals
Utili TH f th i ti ti f t t h iUtilize THz waves for the investigation of transport mechanisms in membranes1. Detection of changes of dielectric conditions can be very sensitive at high1. Detection of changes of dielectric conditions can be very sensitive at high
frequencies when resonators are employed (e.g., Akalin et al., IEEE Trans. MTT 54, 2006)
2 Th hi h th f th t th t it2. The higher the frequency, the more compact the measurement unit Reduction of the amount of substance needed Parallel operation
G b idGoubau waveguide with immobilized proteoliposomes
Example of a probe platform: Waveguide with resonatorg
11.04.2013 | LOEWE-Schwerpunkt "Sensors towards Terahertz" | Hartmut Roskos | 8
A2 Additional goals and gcooperation
To investigate the behavior of membranes upon excitation by highly intense THz waves
Established knowledge: Strong electrical currents at DC and AC (kHzEstablished knowledge: Strong electrical currents at DC and AC (kHz, MHz) can lead to pore opening in cell membranes (useful for electro-chemotherapy with the anticarcinogen Bleomycin).Lit t i di t th t ill i ti ith GH d TH l d tLiterature indicates that illumination with GHz and THz waves may lead to • depolarization of membranes• permeability for chemical substances
changes of the firing rate of axons (Siegel + Pikov Electr Lett 2010;• changes of the firing rate of axons (Siegel + Pikov, Electr. Lett. 2010; Kawase).
Potential for the active manipulation of cells by THz waves Potential for the active manipulation of cells by THz waves
Cooperation in the consortium: with A1, C2
11.04.2013 | LOEWE-Schwerpunkt "Sensors towards Terahertz" | Hartmut Roskos | 9
A3
Cooperation of Jun.-Prof. (THz sensors) and Jakoby with Julius Kühn Institute –Bundesforschungsinstitut für KulturpflanzenBundesforschungsinstitut für Kulturpflanzen, Abt. Biologischer PflanzenschutzMicrofluidics: Schlaak
11.04.2013 | LOEWE-Schwerpunkt "Sensors towards Terahertz" | Hartmut Roskos | 10
A3 Antiboy antigen reactions
A tib d (I l b li ) P t f th d ti i t A
A3 Antiboy-antigen reactions
Antibody (Immunoglobulin): Part of the adaptive immune system. Are proteins built by B-lymphocytes (a type of white blood cells).
Antigen Antigen: Proteins, carbonhydrates, lipides, etc. attached to the surfaces of foreign objects such as bacteriae, pollen, etc.
AntigenAntigen docking site
j , p ,
Antibody-antigen reactions follow a key-lock principle Effects:principle. Effects: Direct neutralization of antigens Making the foreign substance
Antibody
Making the foreign substance recognizable for phagocytes.
11.04.2013 | LOEWE-Schwerpunkt "Sensors towards Terahertz" | Hartmut Roskos | 11
Antibody
A3 GoalA3 Goal
ELISA E Li k d I b t AELISA: Enzyme-Linked Immunosorbent AssayAntibody-based detection of antigens. After a multi-step procedure, antigens are observable multi step procedure, antigens are observable by a color reaction
Antibody antigen interactions are highlyAntibody-antigen interactions are highly selective.Disadvantage: ELISA and related approaches
i l i d irequire several processing steps, and time.
Goal: To develop a THz sensor with the same sensitivity as ELISA, but higher evaluation speed
11.04.2013 | LOEWE-Schwerpunkt "Sensors towards Terahertz" | Hartmut Roskos | 12
A3 Challenges and gcooperation in consortium
The THz signatures of the antibody-antigen reactions are still largely unknown Systematic studies of their THz properties needed Must make a choice of exemplary reactions for further sensor
developmentdevelopment Need to develop a process technology to deposit and immobilize
antibodies on the relevant sensor structures
Cooperation in consortium: with A1 and C2
11.04.2013 | LOEWE-Schwerpunkt "Sensors towards Terahertz" | Hartmut Roskos | 13
A4A4
Cooperation of Chemistry (Schneider), Materials Scienes (Riedel/Nicoloso),Physics (Elsäßer, Roskos)
11.04.2013 | LOEWE-Schwerpunkt "Sensors towards Terahertz" | Hartmut Roskos | 14
A4 Carbon nanotubes (CNTs) ( )and graphene
Carbon sheets (graphene) and nano-tubes with a thickness of a single atomic layer: Adsorption of gas molecules strongly changes the electrical properties E ll t diti f i
1. Making electrical contacts is very difficult especially in the case of vertically aligned (3D) CNTs utilize THz
Excellent conditions for sensorics
case of vertically aligned (3D) CNTs utilize THz radiation for contactless read-out
2 Th l f b i th TH f2. The plasma frequency can be in the THz frequency regime. Measurements there allow a reliable extraction of the Drude parameters (complex conductivity)
3. Graphene can be patterned Possibly promising for the fabrication of meta-materials and the exploitation of resonances for enhanced sensiti it
11.04.2013 | LOEWE-Schwerpunkt "Sensors towards Terahertz" | Hartmut Roskos | 15
sensitivity
A4 GoalsA4 Goals
• Detection of safety- and environmentally relevant gases such as SO2, CH4, CO, H2 - following adsorption on graphene resp. VA-CNTs - by
t tl d ti it t icontactless conductivity measurements using THz waves (Roskos).
• THz ellipsometry for p ythe determination of the optical constants of functional
I ti ti f th TH ti f
graphene films (Elsäßer).
• Investigation of the THz properties of carbon meta-materials (3D CNTs and graphene) (Roskos).
11.04.2013 | LOEWE-Schwerpunkt "Sensors towards Terahertz" | Hartmut Roskos | 16
A4 Research plan and pcooperation
C b TH iCarbonNano-materials
Optimization of growth
THz sensorics
Broadband THz spectroscopy and THz ellipsometryOptimization of growth
• Dynamical conductivity• Frequency of rotational transitions• Gas-induced resonance shifts • Identification of optimal freq range
PatterningIdentification of optimal freq. range
Sensor functionality• Enhancement of sensitivity by MTM
d fi ld l li tiMeta-materials
(MTM)Functionalization• Integration of molecular-
species-selective docking sites
resonances and field localization• Try to match resonances of MTMs and
molecular rotational transitions• Specificity by functionalization
(MTM) A1, C3
• Specificity by functionalization
Sensor demonstrator“lab on chip”
Compact CW systems
11.04.2013 | LOEWE-Schwerpunkt "Sensors towards Terahertz" | Hartmut Roskos | 17
lab-on-chip B1, B2, B5, C2
A4 Synthesis and patterning y p gof CNTs and graphene
Synthesis of structured 3D CNT arrays and graphene by CVD processesSynthesis of structured 3D CNT arrays and graphene by CVD processes
Graphene
G h d d d hGraphene and doped graphene (TEM, Project: ER-CJülich TUD001)
CN
Ts
Strukturierung
SEM images of various patterned 3D CNT block arrays
11.04.2013 | LOEWE-Schwerpunkt "Sensors towards Terahertz" | Hartmut Roskos | 18
Synthesis and patterningy
A4 First experiments on CNTsA4 First experiments on CNTs
0,3
n
CNT Thickness "Ultra-thin" 90 µm120 µm
THz reflectance of a sheet of vertically aligned CNTs as a function of sheet thickness
0,2
sity
refle
ctio
n µ 143 µm 250 µm 360 µm
Fabry-Perot resonances
0,1
Inte
ns
0 1 2 30,0
Frequency (THz)
Multiple reflections between metal t l t d t i f t l d CNT
11.04.2013 | LOEWE-Schwerpunkt "Sensors towards Terahertz" | Hartmut Roskos | 19
catalyst and top region of entangled CNTs
A5A5
Cooperation of materials sciences (Riedel/Nicoloso) and physics (Elsäßer, Roskos) with Emerson ProcessRoskos) with Emerson Process Management GmbH, Hasselroth
11.04.2013 | LOEWE-Schwerpunkt "Sensors towards Terahertz" | Hartmut Roskos | 20
A5 „Fingerprint“ „ g pspectroscopy of gasses
Exploit signatures of rotational molecular modescomplementary to vibrational
HCN
Maw
illk.
Ein
h.)
complementary to vibrationalspectroscopy in the mid-infrared
Harde et al., J. Phys. Chem. A
ajewski, Labs
orpt
ion
(w
Harde et al., J. Phys. Chem. A
NH3
SO
aser Focu
Ab)
Frequenz (GHz)
SO2
us World, 2(w
illk.
Ein
h.
2008
Abso
rptio
n (
11.04.2013 | LOEWE-Schwerpunkt "Sensors towards Terahertz" | Hartmut Roskos | 21
A
A5 GoalsA5 Goals
THz spectroscopy for industrial applications (in consultation with Emerson Process Management)
Specific targets: Optimization of a continuous-wave measurement system with regard toOptimization of a continuous wave measurement system with regard to
THz output power, wavelength tunability, spectral purity of the emission, long-term stability, compactness and user friendlinessD t i ti f th d t ti li it f i hi h th i Determination of the detection limits for gas species which are otherwise difficult to detect: HF, NH3 etc. Simultaneous in-situ detection of individual gas species in mixtures of g p
gases and of gases with aerosols Compare performance of THz and mid-IR spectroscopy
11.04.2013 | LOEWE-Schwerpunkt "Sensors towards Terahertz" | Hartmut Roskos | 22
A5 Goals and cooperationA5 Goals and cooperation
Distinction between isomers of hydrocarbons, to be utilized for the control of combustion processes In-situ characterization of exhaust gases under the restrictive boundary
conditions of high temperatures, presence of soot, and turbulent gas flowflow Flame spectroscopy
Cooperation in consortium: with A6, B1 (photomixers) und C2
11.04.2013 | LOEWE-Schwerpunkt "Sensors towards Terahertz" | Hartmut Roskos | 23
A6A6
Elsäßer (Physics) Jun.-Prof. (THz systems)( y )Jun.-Prof. (THz sensors)
11.04.2013 | LOEWE-Schwerpunkt "Sensors towards Terahertz" | Hartmut Roskos | 24
A6 THz self mixingA6 THz self-mixing
Present THz detection scheme: Power detection with a bolometer, resp. coherent detection with a
NOW:Novel detection principle
Emitter antenna
resp. coherent detection with a photomixer
E itt d d t t t
Self-mixing: A single photomixer for emission and detection
Emitter and detector antenna
Detector antenna
Delay line Feedback mirror
11.04.2013 | LOEWE-Schwerpunkt "Sensors towards Terahertz" | Hartmut Roskos | 25
mirror
A6 GoalsA6 Goals
Application of this novel approach in sensorics
Ad t Advantages:
• Compact systemL l d d• Less laser power needed
• Simplified alignment
Exploration of the potential of the concept in practical use Exploration of the potential of the concept in practical use
Novel tomographic THz spectroscopy: spectral and three-dimensional spatial resolutiondimensional spatial resolution
11.04.2013 | LOEWE-Schwerpunkt "Sensors towards Terahertz" | Hartmut Roskos | 26
A6 THz tomographyA6 THz tomography
Various materials
Coherent superposition of the emitted and returning radiation in theCoherent superposition of the emitted and returning radiation in the photomixer useful for tomographic reconstruction. Variation of the wavelength allows for spectroscopic identification.
11.04.2013 | LOEWE-Schwerpunkt "Sensors towards Terahertz" | Hartmut Roskos | 27
A6 CooperationA6 Cooperation
Cooperation in consortium: with A5, B1 and B2
Cooperation with external partners:BATOP GmbH (Jena): Photomixers
Sacher Lasertechnik GmbH (Marburg): Dual-wavelength lasers
Dipartimento di Elettronicad ll‘ U i ità di P idell‘ Università di Pavia(Prof. G. Giuliani)
11.04.2013 | LOEWE-Schwerpunkt "Sensors towards Terahertz" | Hartmut Roskos | 28
Summary: yAdvantages of THz sensorics
S t l i th TH i (TH “fi i t “) A4 A5 A6 Spectral resonances in the THz regime (THz “fingerprints“): A4, A5, A6
THz radiation enables contactless determination of dielectric properties: A1-A6A1 A6
Weak and mid-level conductivities can be measured reliably: A4
• (High-frequency) conductivity easy to measure if plasma frequency is in• (High-frequency) conductivity easy to measure if plasma frequency is in the THz region. In this case, real and imaginary parts of conductivity can be determined with high precision.C l id li i b i• Contactless measurements avoid complications by contact resistance and contributions by grain boundaries:
Grain boundaries and contact resistances THz waves measure local influence dc conductivity conductivity
11.04.2013 | LOEWE-Schwerpunkt "Sensors towards Terahertz" | Hartmut Roskos | 29
Summary: yAdvantages of THz sensorics
Increased sensitivity by resonant (metallic) structures, both for guided waves and free-space radiation: A1-A4
High frequency small structures sufficient need only low High frequency small structures sufficient need only low amount of substance under test, parallel operation possible: A1-A4
Meta-materials easy to fabricate: A1-A4y
General: THz technology is in a transitional phase: employs mainstream technlogies, becomes more reliable, compact, cheaper. Specific scientific challenges:
• Coupled resonances (Molecular with geometrical / meta-material) has potential of enhanced sensitivity: A4has potential of enhanced sensitivity: A4
• THz radiation changes membrane potential, possibly a link to electro-chemotherapy active manipulation of cells by GHz-/THz
11.04.2013 | LOEWE-Schwerpunkt "Sensors towards Terahertz" | Hartmut Roskos | 30
waves: A2, A3