Prof. Dr. Hartmut Roskos - LOEWE-Schwerpunkt · A3 Antiboy antigen reactions Atibd(I l b li ) P t f th d ti i t A-antigen reactions Antibody (Immunoglobulin): Part of the adaptive

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)


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


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


Exploitation of substrate wavsWaveguides

A1 Cooperation routes in the pconsortium

A1 A2, A3, A4 Sensor 1Sensor 1

, ,

Sensor 2Sensor 2C2 C3Sensor 3Sensor 3


A2A2

Cooperation Roskos/Krozer with MPI for BiophysicsMikrofluidics: Schlaak Sensor implementation jointly with Jun.-Prof. (THz sensors)


(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


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


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


A3

Cooperation of Jun.-Prof. (THz sensors) and Jakoby with Julius Kühn Institute –Bundesforschungsinstitut für KulturpflanzenBundesforschungsinstitut für Kulturpflanzen, Abt. Biologischer PflanzenschutzMicrofluidics: Schlaak


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.


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


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


A4A4

Cooperation of Chemistry (Schneider), Materials Scienes (Riedel/Nicoloso),Physics (Elsäßer, Roskos)


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


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).


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


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


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


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


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 (


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


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


A6A6

Elsäßer (Physics) Jun.-Prof. (THz systems)( y )Jun.-Prof. (THz sensors)


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


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


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.


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)


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


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


waves: A2, A3

Documents

Prof. Dr. Hartmut Roskos - LOEWE-Schwerpunkt · A3 Antiboy antigen reactions Atibd(I l b li ) P t f th d ti i t A-antigen reactions Antibody (Immunoglobulin): Part of the adaptive