Molecular_JJ printing_NN1 Molecular_JJ printing_NN1 techniques_NN2 ,_, which_DDQ involve_VV0 the_AT direct_JJ transfer_NN1 of_IO molecules_NN2 to_II a_AT1 substrate_NN1 with_IW submicrometre_NNU1 resolution_NN1 ,_, have_VH0 been_VBN extensively_RR developed_VVN over_II the_AT past_JJ decade_NNT1 and_CC have_VH0 enabled_VVN many_DA2 applications_NN2 ._. 
Arrays_NN2 of_IO features_NN2 on_II this_DD1 scale_NN1 have_VH0 been_VBN used_VVN to_TO direct_VVI materials_NN2 assembly_NN1 ,_, in_II nanoelectronics_NN2 ,_, and_CC as_CSA tools_NN2 for_IF genetic_JJ analysis_NN1 and_CC disease_NN1 detection_NN1 ._. 
The_AT past_JJ decade_NNT1 has_VHZ witnessed_VVN the_AT maturation_NN1 of_IO molecular_JJ printing_NN1 led_VVN by_II two_MC synergistic_JJ technologies_NN2 :_: dip-pen_JJ nanolithography_NN1 and_CC soft_JJ lithography_NN1 ._. 
Both_DB2 are_VBR characterized_VVN by_II material_NN1 and_CC substrate_NN1 flexibility_NN1 ,_, but_CCB dip-pen_JJ nanolithography_NN1 has_VHZ unlimited_JJ pattern_NN1 design_NN1 whereas_CS soft_JJ lithography_NN1 has_VHZ limited_VVN pattern_NN1 flexibility_NN1 but_CCB is_VBZ low_JJ in_II cost_NN1 and_CC has_VHZ high_JJ throughput_NN1 ._. 
Advances_NN2 in_II DPN_NP1 tip_NN1 arrays_NN2 and_CC inking_VVG methods_NN2 have_VH0 increased_VVN the_AT throughput_NN1 and_CC enabled_VVN applications_NN2 such_II21 as_II22 multiplexed_JJ arrays_NN2 ._. 
A_AT1 new_JJ approach_NN1 to_II molecular_JJ printing_NN1 ,_, polymer-pen_JJ lithography_NN1 ,_, achieves_VVZ low-cost_JJ ,_, high-throughput_JJ and_CC pattern_NN1 flexibility_NN1 ._. 
This_DD1 Perspective_NN1 discusses_VVZ the_AT evolution_NN1 and_CC future_JJ directions_NN2 of_IO molecular_JJ printing_NN1 ._. 
The_AT past_JJ decade_NNT1 has_VHZ witnessed_VVN the_AT genesis_NN1 and_CC evolution_NN1 of_IO printing_VVG technologies_NN2 capable_JJ of_IO patterning_VVG surfaces_NN2 with_IW features_NN2 smaller_JJR than_CSN 100nm_FO ._. 
These_DD2 capabilities_NN2 are_VBR a_AT1 result_NN1 of_IO simultaneous_JJ advances_NN2 in_II physics_NN1 ,_, chemistry_NN1 ,_, materials_NN2 science_NN1 and_CC nanotechnology_NN1 ._. 
The_AT development_NN1 of_IO tools_NN2 for_IF reducing_VVG feature_NN1 size_NN1 is_VBZ motivated_VVN primarily_RR by_II (_( 1_MC1 )_) the_AT semiconductor_NN1 industry_NN1 's_GE desire_NN1 to_TO continue_VVI increasing_VVG the_AT number_NN1 of_IO transistors_NN2 in_II a_AT1 given_JJ area_NN1 ;_; (_( 2_MC )_) the_AT central_JJ dogma_NN1 of_IO nanotechnology_NN1 ,_, which_DDQ states_VVZ that_CST as_CSA feature_NN1 sizes_NN2 approach_VV0 the_AT nanoscale_NN1 ,_, new_JJ properties_NN2 emerge_VV0 that_CST are_VBR not_XX observed_VVN in_II bulk_NN1 materials_NN2 ;_; and_CC (_( 3_MC )_) biological_JJ studies_NN2 and_CC applications_NN2 made_VVD possible_JJ by_II high-density_JJ bioarrays_NN2 ._. 
As_CSA feature_NN1 size_NN1 approach_NN1 the_AT single-molecule_JJ limit_NN1 ,_, molecular_JJ transport_NN1 ,_, assembly_NN1 and_CC intermolecular_JJ interactions_NN2 become_VV0 dominant_JJ considerations_NN2 and_CC have_VH0 shifted_VVN the_AT science_NN1 of_IO patterning_VVG to_II the_AT chemists_NN2 '_GE domain_NN1 ._. 
Solutions_NN2 to_II the_AT problem_NN1 of_IO nanoscale_NN1 patterning_NN1 being_VBG explored_VVN have_VH0 traditionally_RR included_VVN destructive_JJ ,_, radiative_JJ techniques_NN2 such_II21 as_II22 extreme_JJ UV_JJ lithography_NN1 ,_, soft_JJ X-ray_NN1 lithography_NN1 ,_, electron-beam_JJ lithography_NN1 and_CC focused_VVD ion-beam_JJ writing_NN1 ,_, as_II31 well_II32 as_II33 methods_NN2 such_II21 as_II22 nanoimprint_NN1 lithography_NN1 and_CC certain_JJ types_NN2 of_IO scanning-probe_JJ lithography_NN1 (_( SPL_NP1 )_) ._. 
As_CSA nanopatterning_VVG techniques_NN2 have_VH0 become_VVN increasingly_RR important_JJ to_II chemists_NN2 ,_, materials_NN2 scientists_NN2 and_CC biologists_NN2 ,_, molecular_JJ printing_NN1 capabilities_NN2 ,_, defined_VVN as_CSA processes_VVZ where_RRQ molecules_NN2 or_CC materials_NN2 are_VBR directly_RR transferred_VVN to_II a_AT1 substrate_NN1 of_IO interest_NN1 in_II the_AT form_NN1 of_IO submicrometre_NNU1 features_NN2 with_IW at_RR21 least_RR22 one_MC1 dimension_NN1 on_II the_AT molecular_JJ scale_NN1 ,_, have_VH0 also_RR become_VV0 increasingly_RR important_JJ ._. 
In_II this_DD1 regard_NN1 ,_, two_MC technologies_NN2 --_JJ soft_JJ lithography_NN1 and_CC dip-pen_JJ nanolithography_NN1 (_( DPN_NP1 )_) --_NN1 have_VH0 emerged_VVN as_II the_AT most_RGT widely_RR variety_NN1 of_IO substrates_NN2 ._. 
This_DD1 perspective_NN1 discusses_VVZ the_AT history_NN1 and_CC applications_NN2 of_IO molecular_JJ printing_NN1 ,_, focusing_VVG primarily_RR on_II DPN_NP1 and_CC soft_JJ lithography_NN1 as_II the_AT first_MD and_CC most_RGT widely_RR used_JJ techniques_NN2 ,_, and_CC the_AT recent_JJ development_NN1 of_IO polymer-en_FW lithography_NN1 (_( PPL_NP1 )_) ,_, a_AT1 molecular_JJ printing_NN1 method_NN1 that_CST combines_VVZ the_AT advantages_NN2 of_IO soft_JJ lithography_NN1 and_CC DPN_NP1 into_II a_AT1 single_JJ lithographic_JJ platform_NN1 ._. 
Emergence_NN1 of_IO dip-pen_JJ nanolithography_NN1 In_II the_AT early_JJ 1980s_MC2 ,_, new_JJ methods_NN2 for_IF shrinking_JJ feature_NN1 sizes_NN2 of_IO patterns_NN2 on_II silicon_NN1 substrates_NN2 were_VBDR being_VBG actively_RR pursued_VVN by_II the_AT semiconductor_NN1 industry_NN1 as_CSA it_PPH1 became_VVD apparent_JJ that_CST photolithography_NN1 could_VM not_XX continue_VVI to_TO indefinitely_RR reduce_VVI the_AT sizes_NN2 of_IO features_NN2 as_CSA predicted_VVN by_II Moore_NP1 's_GE Law_NN1 and_CC desired_VVN by_II electronics_NN1 manufacturers_NN2 ._. 
The_AT brisk_JJ rate_NN1 of_IO feature-size_JJ reduction_NN1 in_II CMOS_NP1 devices_NN2 demanded_VVD new_JJ ways_NN2 to_TO address_VVI and_CC image_NN1 these_DD2 nanoscale_NN1 structures_NN2 as_II the_AT existing_JJ technologies_NN2 were_VBDR no_RR21 longer_RR22 compatible_JJ with_IW the_AT smaller_JJR features_NN2 ._. 
During_II this_DD1 period_NN1 ,_, scanning_VVG probe_NN1 microscopes_NN2 (_( SPMs_NP1 )_) ,_, specially_RR the_AT scanning_NN1 tunnelling_NN1 microscope_NN1 (_( STM_NN1 )_) and_CC atomic_JJ force_NN1 microscope_NN1 (_( AFM_NP1 )_) ,_, emerged_VVD as_CSA imaging_VVG and_CC spectroscopic_JJ tools_NN2 that_CST probe_VV0 the_AT topology_NN1 of_IO surfaces_NN2 using_VVG nanosized_JJ tips_NN2 that_CST raster_NN1 across_II them_PPHO2 by_II piezoelectric_JJ actuation_NN1 ._. 
SPMs_NP1 have_VH0 revolutionized_VVN surface_NN1 science_NN1 and_CC even_RR enabled_VVD the_AT manipulation_NN1 of_IO surfaces_NN2 at_II the_AT single-atom_JJ level_NN1 ._. 
For_IF the_AT development_NN1 of_IO the_AT SPM_NP1 ,_, Binnig_NP1 and_CC Rohrer_NP1 were_VBDR awarded_VVN the_AT Nobel_NP1 Prize_NN1 in_II Physics_NN1 in_II 1986_MC ._. 
Immediately_RR following_VVG the_AT invention_NN1 of_IO SPMs_NP1 ,_, researchers_NN2 began_VVD using_VVG these_DD2 machines_NN2 for_IF patterning_VVG surfaces_NN2 ,_, marking_VVG the_AT birth_NN1 of_IO SPL_NP1 ._. 
A_AT1 major_JJ milestone_NN1 in_II SPL_NP1 development_NN1 occurred_VVD when_RRQ Eigler_NP1 and_CC co-workers_NN2 used_VVD an_AT1 STM_NN1 to_II pattern_NN1 individual_JJ atoms_NN2 on_II a_AT1 surface_NN1 ,_, suggesting_VVG that_CST SPMs_NP1 could_VM indeed_RR be_VBI used_VVN for_IF molecular_JJ printing_NN1 or_CC perhaps_RR even_RR manufacturing_NN1 ._. 
In_II this_DD1 experiment_NN1 ,_, the_AT researchers_NN2 repositioned_VVD individual_JJ Xe_NN1 atoms_NN2 on_II a_AT1 single-crystal_JJ Ni_NP1 surface_NN1 to_TO form_VVI the_AT letters_NN2 "_" IBM_NP1 "_" using_VVG an_AT1 STM_NN1 tip_NN1 at_II 4_MC K._NP1 At_II this_DD1 temperature_NN1 ,_, the_AT van_NP1 der_NP1 Waals_NP1 forces_NN2 and_CC electrostatic_JJ interactions_NN2 between_II the_AT atoms_NN2 and_CC the_AT surface_NN1 are_VBR greater_JJR than_CSN the_AT interactions_NN2 between_II the_AT tip_NN1 and_CC the_AT atom_NN1 ,_, thereby_RR keeping_VVG the_AT atoms_NN2 anchored_VVN to_II the_AT surface_NN1 while_CS they_PPHS2 are_VBR dragged_VVN to_II their_APPGE intended_JJ sites_NN2 with_IW the_AT tip_NN1 ._. 
Subsequently_RR ,_, the_AT IBM_NP1 group_NN1 showed_VVD that_CST this_DD1 patterning_JJ technique_NN1 could_VM be_VBI used_VVN to_TO study_VVI fundamental_JJ surface_NN1 properties_NN2 as_II a_AT1 result_NN1 of_IO the_AT atomic_JJ resolution_NN1 aorded_VVD by_II the_AT STM_NN1 ._. 
By_II arranging_VVG 48_MC Fe_NP1 atoms_NN2 in_II a_AT1 circular_JJ structure_NN1 on_II a_AT1 Cu(111)_FO surface_NN1 ,_, they_PPHS2 were_VBDR able_JK to_TO observe_VVI standing_NN1 electron_NN1 waves_NN2 within_II the_AT circular_JJ corral_NN1 at_II 4_MC K._NP1 STM_NN1 repositioning_NN1 was_VBDZ extended_VVN to_II molecules_NN2 as_RR21 well_RR22 ,_, and_CC a_AT1 molecular_JJ counting_NN1 device_NN1 was_VBDZ fabricated_VVN by_II sequentially_RR moving_VVG a_AT1 row_NN1 of_IO 10_MC fullerenes_NN2 on_II a_AT1 Cu(111)_FO surface_NN1 ._. 
Although_CS these_DD2 impressive_JJ studies_NN2 demonstrate_VV0 the_AT potential_NN1 of_IO SPMs_NP1 as_CSA patterning_VVG tools_NN2 ,_, they_PPHS2 also_RR emphasize_VV0 their_APPGE limitations_NN2 and_CC impracticality_NN1 ._. 
Specially_RR ,_, this_DD1 approach_NN1 (_( 1_MC1 )_) requires_VVZ controlled_JJ environments_NN2 and_CC low_JJ temperatures_NN2 ;_; (_( 2_MC )_) is_VBZ painstakingly_RR slow_JJ and_CC indirect_JJ in_II nature_NN1 ,_, as_CSA it_PPH1 requires_VVZ the_AT picking_VVG up_RP and_CC subsequent_JJ movement_NN1 of_IO atoms_NN2 ;_; and_CC (_( 3_MC )_) is_VBZ not_XX easily_RR scaled_VVN ._. 
However_RR ,_, the_AT work_NN1 by_II Eigler_NP1 ,_, no_RGQV31 matter_RGQV32 how_RGQV33 impractical_JJ ,_, demonstrated_VVD the_AT ultimate_JJ resolution_NN1 of_IO SPL_NP1 techniques_NN2 --_JJ atom-by-atom_JJ construction_NN1 of_IO nanopatterns_NN2 --_NN1 and_CC established_VVD a_AT1 challenge_NN1 for_IF the_AT research_NN1 community_NN1 to_TO develop_VVI rapid_JJ ways_NN2 of_IO printing_VVG atom-_JJ and_CC molecule-based_JJ structures_NN2 on_II a_AT1 surface_NN1 with_IW nanoscale_NN1 resolution_NN1 ._. 
For_IF the_AT next_MD decade_NNT1 ,_, scientists_NN2 followed_VVD the_AT model_NN1 of_IO the_AT semi-conductor_NN1 industry_NN1 and_CC developed_VVD a_AT1 series_NN of_IO indirect_JJ SPL_NP1 methods_NN2 ,_, which_DDQ focus_VV0 on_II the_AT delivery_NN1 of_IO energy_NN1 rather_II21 than_II22 molecules_NN2 to_II a_AT1 surface_NN1 to_TO create_VVI functional_JJ patterns_NN2 ,_, typically_RR with_IW the_AT aid_NN1 of_IO a_AT1 resist_VV0 material_NN1 ._. 
Taking_VVG advantage_NN1 of_IO the_AT registration_NN1 enabled_VVN by_II piezo-actuation_NN1 and_CC the_AT anoscale_NN1 radii_NN2 of_IO the_AT tips_NN2 ,_, scientists_NN2 were_VBDR able_JK to_TO generate_VVI sub-50-nm_FU features_NN2 by_II scratching_NN1 ,_, etching_VVG and_CC oxidizing_VVG surfaces_NN2 ._. 
For_REX21 example_REX22 ,_, dynamic_JJ plough_NN1 lithography_NN1 can_VM be_VBI used_VVN to_TO scratch_VVI polymer-coated_JJ silicon_NN1 surfaces_NN2 ,_, which_DDQ can_VM be_VBI subsequently_RR processed_VVN using_VVG conventional_JJ silicon_NN1 wet_JJ etching_NN1 ._. 
A_AT1 process_NN1 known_VVN as_II nanoshaving_VVG or_CC nanografting_NN1 uses_VVZ the_AT tip_NN1 of_IO an_AT1 AFM_NN1 and_CC an_AT1 applied_JJ force_NN1 to_TO remove_VVI a_AT1 molecular_JJ monolayer_NN1 on_II gold_NN1 in_II a_AT1 site-specific_JJ fashion_NN1 ._. 
Anodic_JJ oxidation_NN1 of_IO silicon_NN1 was_VBDZ developed_VVN by_II Quate_NN1 for_IF patterning_VVG silicon_NN1 substrates_NN2 ._. 
Sagiv_NP1 et_RA21 al_RA22 ._. 
pioneered_VVN a_AT1 related_JJ approach_NN1 ,_, which_DDQ uses_VVZ an_AT1 applied_JJ bias_NN1 between_II a_AT1 conductive_JJ AFM_JJ tip_NN1 and_CC an_AT1 monolayer_NN1 ,_, to_TO electro-chemically_RR convert_VVI methyl_NN1 groups_NN2 to_II acids_NN2 ._. 
The_AT reactive_JJ acid_NN1 groups_NN2 are_VBR used_VVN for_IF subsequent_JJ chemistry_NN1 and_CC molecular_JJ immobilization_NN1 ._. 
Such_DA techniques_NN2 have_VH0 important_JJ applications_NN2 but_CCB are_VBR limited_VVN by_II their_APPGE indirect_JJ nature_NN1 and_CC challenges_NN2 associated_VVN with_IW parallelization_NN1 ._. 
A_AT1 problem_NN1 in_II developing_VVG any_DD SPL_NP1 or_CC scanning_VVG probe_NN1 imaging_NN1 technique_NN1 that_CST functions_NN2 in_II air_NN1 ,_, is_VBZ dealing_VVG with_IW the_AT consequences_NN2 of_IO the_AT capillary_JJ effect_NN1 and_CC meniscus_NN1 formation_NN1 ._. 
These_DD2 factors_NN2 convolute_JJ measurements_NN2 taken_VVN with_IW scanning_VVG probe_NN1 instruments_NN2 ,_, and_CC therefore_RR many_DA2 scientists_NN2 rely_VV0 on_II ultrahigh_NN1 vacuum_NN1 for_IF their_APPGE experiments_NN2 ._. 
Surprisingly_RR ,_, the_AT controlled_JJ direct_JJ transfer_NN1 of_IO material_NN1 to_II a_AT1 surface_NN1 with_IW nanoscale_NN1 precision_NN1 was_VBDZ not_XX realized_VVN until_II 1999_MC when_RRQ alkanethiols_NN2 were_VBDR deposited_VVN on_II gold_NN1 substrates_NN2 ,_, with_IW the_AT use_NN1 of_IO humidity_NN1 and_CC the_AT meniscus_NN1 to_TO facilitate_VVI transport_NN1 and_CC generate_VVI stable_JJ chemisorbed_JJ nanostructures_NN2 ,_, marking_VVG the_AT invention_NN1 of_IO DPN_NP1 ._. 
Interestingly_RR ,_, a_AT1 few_DA2 years_NNT2 earlier_RRR ,_, others_NN2 had_VHD attempted_VVN what_DDQ seemed_VVD to_TO be_VBI a_AT1 nearly_RR identical_JJ experiment_NN1 and_CC concluded_VVD that_DD1 transport_NN1 did_VDD not_XX occur_VVI ._. 
The_AT stronger_JJR interactions_NN2 between_II the_AT thiols_NN2 and_CC gold_NN1 at_II room_NN1 temperature_NN1 ,_, compared_VVN with_IW the_AT weak_JJ interactions_NN2 between_II the_AT tip_NN1 and_CC the_AT ink_NN1 ,_, were_VBDR key_JJ to_II forming_VVG stable_JJ patterns_NN2 on_II the_AT surface_NN1 ._. 
The_AT versatility_NN1 of_IO this_DD1 method_NN1 ,_, using_VVG direct_JJ molecular_JJ transport_NN1 from_II a_AT1 tip_NN1 to_II a_AT1 surface_NN1 to_TO form_VVI patterns_NN2 ,_, was_VBDZ immediately_RR apparent_JJ ,_, and_CC in_II the_AT decade_NNT1 since_CS its_APPGE invention_NN1 ,_, DPN_NP1 has_VHZ been_VBN used_VVN to_TO generate_VVI structures_NN2 made_VVN of_IO organometallic_JJ molecules_NN2 ,_, polymers_NN2 ,_, DNA_NN1 ,_, proteins_NN2 ,_, peptides_NN2 and_CC affinity_NN1 templates_NN2 ,_, which_DDQ allow_VV0 for_IF the_AT subsequent_JJ immobilization_NN1 of_IO viruses_NN2 ,_, colloidal_JJ nano-particles_NN2 ,_, metal_NN1 ions_NN2 and_CC single-walled_JJ carbon_NN1 nanotubes_VVZ on_II many_DA2 types_NN2 of_IO surfaces_NN2 ._. 
Furthermore_RR ,_, DPN_NP1 has_VHZ enabled_VVN fundamental_JJ studies_NN2 related_VVN to_II molecular_JJ transport_NN1 ,_, and_CC the_AT fabrication_NN1 of_IO technological_JJ tools_NN2 such_II21 as_II22 photomasks_NN2 ,_, gas_NN1 sensors_NN2 and_CC biological_JJ screening_NN1 devices_NN2 ,_, including_II an_AT1 assay_NN1 for_IF human_JJ immunodeficiency_NN1 HIV-1_NN1 virus_NN1 p24_FO antigen_NN1 in_II serum_NN1 samples_NN2 and_CC gene_NN1 chips_NN2 ._. 
DPN_NP1 relies_VVZ on_II the_AT spontaneous_JJ formation_NN1 of_IO a_AT1 meniscus_NN1 between_II the_AT tip_NN1 and_CC surface_NN1 ,_, which_DDQ serves_VVZ as_II a_AT1 conduit_NN1 for_IF ink_NN1 transport_NN1 ._. 
The_AT deposition_NN1 rate_NN1 is_VBZ a_AT1 function_NN1 of_IO tip-substrate_JJ contact_NN1 time_NNT1 ,_, the_AT ink_NN1 diffusion_NN1 coefficient_NN1 ,_, and_CC the_AT ink_NN1 coverage_NN1 on_II the_AT pen_NN1 ._. 
Under_II appropriate_JJ conditions_NN2 ,_, feature_NN1 sizes_NN2 can_VM be_VBI controlled_VVN on_II the_AT sub-50-nm_FU to_II many-micrometre_JJ length_NN1 scale_NN1 ._. 
Patterns_NN2 are_VBR formed_VVN by_II moving_VVG the_AT tip_NN1 across_II the_AT surface_NN1 at_II a_AT1 controlled_JJ velocity_NN1 ,_, and_CC piezo-actuation_NN1 on_II three_MC axes_NN2 provides_VVZ near-perfect_JJ registration_NN1 ._. 
Because_CS the_AT piezo-actuators_NN2 are_VBR computer_NN1 controlled_VVD ,_, arbitrary_JJ patterns_NN2 can_VM be_VBI formed_VVN by_II the_AT movement_NN1 of_IO the_AT tip_NN1 ,_, which_DDQ can_VM not_XX be_VBI done_VDN by_II so_RR lithography_NN1 ,_, where_CS the_AT pattern_NN1 is_VBZ predetermined_VVN by_II a_AT1 mould_NN1 ._. 
By_II increasing_VVG the_AT rastering_JJ speed_NN1 of_IO the_AT tip_NN1 across_II the_AT surface_NN1 ,_, the_AT transport_NN1 of_IO molecules_NN2 is_VBZ halted_VVN ,_, and_CC the_AT same_DA probe_NN1 tip_VV0 that_DD1 is_VBZ used_VVN for_IF writing_NN1 ,_, acts_VVZ instead_RR as_II an_AT1 imaging_NN1 tool_NN1 rather_II21 than_II22 a_AT1 pen_NN1 to_TO provide_VVI feedback_NN1 on_II the_AT pattern_NN1 quality_NN1 ._. 
Finally_RR ,_, materials_NN2 that_CST are_VBR resistant_JJ to_TO transport_VVI in_II a_AT1 conventional_JJ DPN_NP1 experiment_NN1 can_VM be_VBI dispersed_VVN in_II a_AT1 hydrophilic_JJ or_CC lipophilic_JJ carrier_NN1 matrix_NN1 that_CST assists_VVZ their_APPGE movement_NN1 through_II the_AT meniscus41_FO ._. 
Importantly_RR ,_, there_EX is_VBZ no_AT need_NN1 to_TO expose_VVI the_AT substrate_NN1 to_II harsh_JJ ultraviolet_JJ ,_, ion-_JJ or_CC electron-beam_JJ radiation_NN1 ,_, characteristic_NN1 of_IO indirect_JJ patterning_JJ techniques_NN2 ,_, and_CC therefore_RR DPN_NP1 can_VM be_VBI used_VVN to_TO print_VVI fragile_JJ or_CC reactive_JJ organic_JJ and_CC biological_JJ materials_NN2 ._. 
These_DD2 advantages_NN2 of_IO DPN_NP1 are_VBR responsible_JJ for_IF its_APPGE rapid_JJ development_NN1 and_CC dissemination_NN1 over_II the_AT past_JJ decade_NNT1 ,_, however_RR ,_, in_II the_AT early_JJ stages_NN2 of_IO its_APPGE development_NN1 ,_, DPN_NP1 faced_VVD many_DA2 of_IO the_AT same_DA drawbacks_NN2 as_CSA surface-destructive_JJ indirect_JJ SPLs_NP1 ,_, primarily_RR poor_JJ throughput_NN1 ,_, a_AT1 concern_NN1 that_CST soon_RR would_VM become_VVI a_AT1 major_JJ focus_NN1 of_IO DPN_NP1 research_NN1 ._. 
High-throughput_JJ molecular_JJ printing_NN1 with_IW soft_JJ lithography_NN1 So_RR lithography_NN1 is_VBZ a_AT1 complementary_JJ molecular_JJ printing_NN1 technique_NN1 that_CST overcomes_VVZ the_AT throughput_NN1 problem_NN1 associated_VVN with_IW the_AT early_JJ incarnations_NN2 of_IO DPN_NP1 ._. 
Specially_RR ,_, microcontact_VV0 printing_NN1 (_( Cp_NP1 )_) ,_, a_AT1 form_NN1 of_IO so_RR lithography_NN1 ,_, uses_VVZ an_AT1 elastomer_NN1 stamp_NN1 ,_, typically_RR fabricated_VVN by_II conventional_JJ lithographic_JJ methods_NN2 ,_, to_TO directly_RR transfer_VVI materials_NN2 to_II a_AT1 surface_NN1 of_IO interest_NN1 ._. 
The_AT Cp_NP1 approach_NN1 has_VHZ flourished_VVN as_II a_AT1 research-grade_JJ molecular_JJ printing_NN1 technology_NN1 because_II21 of_II22 its_APPGE ease_NN1 of_IO use_NN1 ,_, low_JJ cost_NN1 ,_, and_CC high_JJ throughput_NN1 ._. 
It_PPH1 has_VHZ become_VVN the_AT poor_JJ man_NN1 's_GE replacement_NN1 for_IF photolithography_NN1 ,_, allowing_VVG researchers_NN2 in_II many_DA2 fields_NN2 to_TO use_VVI micro-_JJ and_CC nanofabrication_NN1 ._. 
In_II Cp_NP1 ,_, elastomeric_JJ stamps_NN2 are_VBR prepared_VVN by_II pouring_VVG an_AT1 elastomer_NN1 ,_, including_II poly(dimethylsiloxane)_NN1 (_( PDMS_NP1 )_) ,_, polyurethanes_NN2 ,_, polyimides_NN2 and_CC natural_JJ polymers_NN2 such_II21 as_II22 agarose_NN1 ,_, in_II a_AT1 mould_NN1 prepared_VVN by_II conventional_JJ photolithographic_JJ methods_NN2 ._. 
The_AT polymer_NN1 is_VBZ cured_VVN in_II the_AT mould_NN1 ,_, thereby_RR generating_VVG a_AT1 relief_NN1 structure_NN1 in_II the_AT elastomeric_JJ stamp_NN1 ._. 
The_AT stamp_NN1 can_VM then_RT be_VBI used_JJ to_II pattern_NN1 proteins_NN2 ,_, DNA_NN1 ,_, cells_NN2 ,_, alkanethiols_NN2 ,_, silanes_NN2 ,_, colloids_NN2 and_CC salts_NN2 on_II a_AT1 variety_NN1 of_IO at_II as_RG well_RR as_CSA curved_JJ surfaces_NN2 ._. 
The_AT Cp_NP1 technique_NN1 ,_, however_RR ,_, has_VHZ several_DA2 limitations_NN2 ._. 
Although_CS the_AT stamps_NN2 can_VM print_VVI over_RP large_JJ areas_NN2 ,_, they_PPHS2 can_VM only_RR deposit_VVI a_AT1 single_JJ pattern_NN1 that_CST is_VBZ predetermined_VVN by_II the_AT stamp_NN1 ._. 
Therefore_RR ,_, a_AT1 new_JJ mould_NN1 must_VM be_VBI fabricated_VVN each_DD1 time_NNT1 a_AT1 new_JJ pattern_NN1 is_VBZ desired_VVN ._. 
Feature_NN1 size_NN1 control_NN1 is_VBZ affected_VVN and_CC limited_VVN by_II stamp_NN1 swelling_VVG and_CC shrinking_NN1 ,_, both_RR during_II curing_VVG and_CC stamp_VV0 inking_VVG ._. 
The_AT mechanical_JJ properties_NN2 of_IO the_AT stamps_NN2 can_VM also_RR limit_VVI design_NN1 flexibility_NN1 ._. 
For_REX21 example_REX22 ,_, the_AT softness_NN1 of_IO the_AT elastomer_NN1 limits_VVZ the_AT aspect_NN1 ratio_NN1 ,_, height/length_NN1 (_( h/l_ZZ1 )_) ,_, of_IO the_AT features_NN2 ._. 
If_CS the_AT feature_NN1 aspect_NN1 ratio_NN1 on_II the_AT stamp_NN1 is_VBZ not_XX between_II 0.2_MC and_CC 2_MC ,_, bending_VVG of_IO the_AT stamp_NN1 can_VM cause_VVI pattern_NN1 defects_NN2 ,_, and_CC ,_, for_IF features_NN2 that_CST are_VBR too_RG widely_RR separated_VVN (_( 20h_FO )_) ,_, sagging_VVG of_IO the_AT stamp_NN1 causes_VVZ defects_NN2 ._. 
Indeed_RR ,_, the_AT fabrication_NN1 of_IO alkanethiol_NN1 features_VVZ smaller_JJR than_CSN 150_MC nm_FU is_VBZ a_AT1 significant_JJ challenge_NN1 using_VVG conventional_JJ methods_NN2 ._. 
By_II using_VVG DPN_NP1 to_TO introduce_VVI chemical_JJ modications_NN2 on_II a_AT1 flat_JJ PDMS_NP1 stamp_NN1 and_CC by_II passivating_VVG the_AT surrounding_JJ areas_NN2 with_IW a_AT1 perfluorinated_JJ monolayer_NN1 ,_, we_PPIS2 have_VH0 helped_VVN overcome_VVI this_DD1 deficiency_NN1 ,_, and_CC shown_VVN that_CST features_VVZ as_RG small_JJ as_CSA 80nm_FO could_VM be_VBI easily_RR prepared_VVN with_IW aspect_NN1 ratios_NN2 as_RG low_JJ as_CSA 0.01._MC is_VBZ study_NN1 underscores_VVZ the_AT synergistic_JJ aspects_NN2 of_IO so_RR lithography_NN1 and_CC DPN_NP1 ._. 
